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# Vehicle Ancillary Load Reduction Project Close-Out Report

An Overview of the Task and a Compilation of the Research Results

J. Rugh and R. Farrington Technical Report
NREL/TP-540-42454 January 2008

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# Vehicle Ancillary Load Reduction Project Close-Out Report

An Overview of the Task and a Compilation of the Research Results

J. Rugh and R. Farrington

Prepared under Task No. FC07.5000 Technical Report
NREL/TP-540-42454 January 2008NOTICE

This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

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### Acknowledgements

The authors gratefully acknowledge the support fo r this work provided by Ed Wall, Rogelio Sullivan, Lee Slezak, and others in the Vehicle Technologies Program of the U.S. Department of Energy’s (DOE) Office of Energy Effici ency and Renewable Energy, as well as past support from Bob Kirk, Bob Kost, and Roland Grav el of DOE. The authors also appreciate the support of Terry Penney, Technology Ma nager in the National Renewable Energy Laboratory (NREL) Renewable Fuels Scienc e and Technology Directorate, and Barbara Goodman, Director of NREL’s Center for Transportation Technologies and Systems.

This project might not have been possible w ithout initial funding from NREL’s laboratorydirected research and development (R&D) program and the support of Admiral Richard Truly, NREL’s Director at the project’s inception.

We also acknowledge our close collaboration w ith the automotive industry and the strong support provided by our industr ial R&D partners. We benef ited greatly from our many interactions with industry and appreciate the challenges they face in order to deliver highquality products in increasingly shorter time frames.

In addition, we would like to recognize th e many NREL project team members who contributed so much to the program’s acco mplishments. They include the following (in alphabetical order): Greg Barber, Desikan Bhar athan, Dan Blake, Adam Boyts, Steve Burch, Larry Chaney, Matt Cuddy, Rob Farrington, S ean Gooding, Terry Hendricks, Valerie Johnson Hovland, Matt Keyser, Charlie King, Rom Mc Guffin, Aaron Oakley, Ken Proc, Cassie Quaintance, John Rugh, and Tom Thoensen.

Finally, we want to acknowledge the signif icant contributions of ADAM, the sophisticated
thermal manikin.

iii

### Executive Summary

The amount of fuel used for climate control in vehicles affects our na tion’s energy security significantly as it lowers the fuel economy of the 230 million light-duty conventional vehicles in use in the United States today. Researchers at the National Renewable Energy Laboratory (NREL), a U.S. Department of Energy (DOE) national laboratory, have estimated that the United States consumes about 7 billion gallons of fuel per year just to air-condition light-duty vehicles. Therefore, the primary mission of NREL’s Vehicle Ancillary Load Reduction Task was to develop and evaluate technologies that reduce the amount of fuel used for automobile air-conditioning (A/C). This report summarizes the results of evaluations, conducted over the last 10 years, of technolog ies and techniques for reducin g A/C fuel consumption.

NREL’s researchers used a variety of tools to research and develop innovative techniques and technologies that reduce the amount of fuel needed for a vehicle’s ancillary loads. Specifically, their efforts have led to the following:

• Development and testing of ancillary load reduction technologies for reducing A/C fuel consumption while keeping occupants comfortable

• Development of a passenger compartment c ooling system using waste heat as an

energy source.

In addition to its impact on the fuel economy of conventional vehicles, A/C can reduce the fuel economy of advanced vehicles by as much as 35%, which in turn can increase their fuel consumption as much as 50%. To address th ese issues, NREL worked closely with the automotive industry to develop techniques to redu ce ancillary loads, such as climate control, in vehicles. We conducted research to impr ove vehicle efficiency and fuel economy by controlling the climate in the vehicle while keeping passengers comfortable. As part of this effort, we conducted research in integrated modeling, optimized techniques to deliver conditioned air to vehicle occupants, condu cted thermophysiological modeling, and investigated waste-heat cooling and heating opportunities.

There is great potential to reduce A/C fuel consumption because A/C systems have traditionally been designed to maximize capaci ty, not efficiency. Therefore, among other modeling activities, we used an integrated vehicle thermal modeling process to estimate the potential reduction in A/C system size and fuel use resulting from the use of solar reflective glass and solar-powered parked-car ventilation (reducing capacity). Using a Cadillac STS as an example vehicle, we deter mined that the vehicle’s A/C cooling capacity of 5.7 kW could be reduced by 30% to 4.0 kW while mainta ining a cooldown performance of 30 minutes. A vehicle simulation showed that reducing th e A/C load by 30% decreased A/C fuel consumption by 26%.

Reducing Thermal Loads When a vehicle is parked, typically 50% to 75% of the thermal energy entering the passenger compartment is from the solar energy transmitted and absorbed by window glazing. Reflecting the solar radiation incident on the ve hicle’s glass is a critical step in making significant reductions in the thermal loads. Lower thermal loads make it possible to reduce the capacity of the A/C system.

ivAs part of the Improved Mobile Air Conditioning Cooperative Research Program (I-MAC), NREL tested a new type of solar-reflective gl ass that improved the reflection of the nearinfrared (IR) portion of the solar spectru m on a 2005 Cadillac STS. The Sungate EP automotive glass allowed only 3% of the IR energy to be transmitted through the glass. Using this technology at all glazing locations reduced the average air temperature by 7.1°C (12.8°F), the seat temperature by 8.7°C (15.7°F), the windshield temperature by 19.3°C (24.7°F), and the instrument panel surface temperature by 14.6°C (26.3°F).

Another way to assess these data is in terms of maximum possible temperature reductions, in other words, the difference between a baseline vehicle’s average air temperature and ambient. Using solar-reflective glass in all locations reduced the average air temperature by 34% of the maximum possible, and the seat temperature by 35%. Using reflective shades and electrochromic switchable glazing are also effective techniques for reducing the solar energy entering the passenger compartment. We also found that solar-reflective coatings on exterior opaque surfaces and body insulation can reduce a vehicle’s interior temperatures, but to a lesser extent than solar-reflective glazing, shades, and parked-car ventilation can. Heat pipes were found to significantly reduce instrument panel (IP), windshield, and air temperatures.

Improving Ventilation Because solar energy entering a vehicle heats the interior mass of the passenger compartment, which in turn heats the air, venting the warm air and pulling in cooler ambient air can reduce the temperature of the vehicle’s interior. Therefore, NREL tested various natural and forced ventilation techniques for parked cars on a 2000 J eep Grand Cherokee. The data showed that using strategically located air inlets for natu ral convection induced flow can be nearly as effective as using forced convection ventila tion with the heating, ventilating, and airconditioning (HVAC) blower speed set to me dium. With the sunroof open 6 cm and floor inlets, buoyancy induced flow reduced the cabi n’s air temperature by 5.7oC, a reduction of 38% of the maximum possible. In contrast, operating the HVAC blower on the medium setting reduced the average air temperature by 6.9oC.

We also tested a solar-powered ventilation system for a parked car as part of I-MAC thermal soak testing on the Cadillac STS. The average ai r temperature was reduced 5.6oC, and the seat temperatures were reduced 5o-6oC when air was exhausted from the vehicle. These represented 26% and 21% of the maximum possi ble temperature reductions, respectively. Using interior window shades to block solar radiation can result in a warm layer of air between the window and shade. So, we investigat ed ventilation strategies that exhaust this warm air and prevent it from mixing with the air in the cabin.

Using Innovative Cooling Technologies Conventional vehicles generate wa ste heat typically equivalent to 60% to 80% of the chemical energy in the fuel. Therefore, we investigated capturing a vehicle’s waste heat using thermoacoustics to power a cabin cooling sy stem. We also devel oped a thermoelectric analysis tool to assess the feasibility and performance of thermoelectric waste heat recovery
systems.

The A/C system control strategy used is an im portant factor in a vehicle’s overall energy consumption. Overcooling and then reheating air to control the temperature of the cabin is a

vmethod commonly used in vehicles with automatic temperature control. But this is not an effective energy-conservation practice. Using recirculated cabin air reduces energy use by avoiding the need to cool hot and humid outside air, but the air quality must remain acceptable. To address these issues, we devel oped a photocatalytic oxidation technique that reduced volatile organic compounds and odors in a vehicle’s cabin and increased air
recirculation rates.

In addition, conventional automotive seats in sulate the occupant thermally and reduce evaporative cooling by means of perspiration, t hus increasing the temperature of the contact between the occupant and the seat. Both actively ventilated seats and mesh seats are potentially low-energy approaches to improving thermal comfort and achieving more efficient climate control. Using a ventilated seat resulted in an overall thermal sensation improvement of 0.28, on a scale of +4 to -4. We estimate that this technique could allow the capacity of the A/C system to be reduced by 7% and still maintain thermal comfort. This would reduce A/C fuel consumption by 7.5%.

Conclusions and Recommendations The thermal load-reduction technologies that we tested are available for today’s vehicles. If they are incorporated along with a smaller A/C system, or they result in less frequent use of air-conditioning, America’s drivers will save money while remaining comfortable. In addition, fuel-use reductions translate directly to lower carbon dioxide (CO 2 ) emissions. Since this project’s inception, concerns about global warming have increased. These concerns have prompted new legislation and re quirements to use alternative re frigerants and include A/C in
vehicle CO 2 calculations. While automotive manufacturers and suppliers are redesigning A/C systems, they have a unique opportunity to in corporate thermal load-reduction technologies and improved efficiency components in the new designs.

This project has been successful for many di fferent reasons. For example, NREL developed
several new tools that weren’t available previously, such as VSOLE, the National A/C Fuel Use Model, a sophisticated thermal comfort manikin (ADAM) controlled by a high-resolution model of the human thermoregulatory system, and a transient thermal comfort model. NREL also conducted objective evaluations of advanced technologies in a vehicle context. And we provided a means of modeling and testing componen ts in a systems context to determine their performance and impact on A/C fuel consumption. Based on the insights we have gained on significantly reducing A/C system fuel cons umption, we recommend the following steps in this R&D pathway:

1. Reduce the thermal load by using solar-reflective glass or shades and parked-car
ventilation.
2. Incorporate low-mass, naturally ventilated seating (or active climate-control seating).
3. Incorporate the most efficien t A/C components available.
4. Increase the use of recirculated air to the maximum extent possible, considering air quality, dehumidification, and safety issues, while avoidi ng condensation on windows.

5. Eliminate the overcooling and subsequent reheating of air that occurs now to achieve the desired temperature in vehicles with automatic temperature control systems.

vi

### Table of Contents

1.0 Introduction ............................................................................................................................. 1 1.1 History

............................................................................................................................... .. 1 1.2 Approach ............................................................................................................................. 1 2.0 Significant Accomplishments ................................................................................................. 3 2.1 Modeling ............................................................................................................................. 3 2.1.1 A/C Fuel Use Analysis ............................................................................................... 3
2.1.2 Transient A/C Model.................................................................................................. 4
2.1.3 VSOLE ....................................................................................................................... 5 2.1.4 Integrated Vehicle Th ermal Modeling Process .......................................................... 6 2.1.5 Integrated Heat Exchanger/Thermoel ectric Power Generation Analysis Tool ........ 10 2.2 Vehicle and Component Testing ....................................................................................... 12 2.2.1 Solar-Reflective Glazing .......................................................................................... 12
2.2.2 Parked-Car Ventilation ............................................................................................ 14 2.2.3 Solar-Reflective Opaque Surface Coatings .............................................................. 16
2.2.4 Window Shades ........................................................................................................ 18
2.2.5 Insulation .................................................................................................................. 19
2.2.6 Climate-Control and Low-Mass Seats ..................................................................... 19 2.2.7 Instrument Panel Heat Pipe Cooling ........................................................................ 22
2.2.8 Waste Heat Utilization: Thermoacoustics ................................................................ 24 2.2.9 Indoor Air Quality .................................................................................................... 27 2.2.10 Boundary Layer Capture ........................................................................................ 29
2.2.11 Electrochromic Sunroof ......................................................................................... 29
2.3 Thermal Comfort Tools .................................................................................................... 30
2.3.1 ADvanced Automotive Manikin .............................................................................. 30 2.3.2 Human Thermal Physiological Model ..................................................................... 32 2.3.3 Human Thermal Comfort Empirical Model ............................................................. 33 2.3.4 Nonautomotive Applications for Thermal Comfort Tools ....................................... 33
2.4 Test Facilities .................................................................................................................... 35 2.4.1 Vehicle Climate Control Laboratory ........................................................................ 35
2.4.2 Manikin Environmental Chamber............................................................................ 37 2.4.3 Waste Heat Utilization Laboratory .......................................................................... 38 2.4.4 Outdoor Testing ....................................................................................................... 40 3.0 Application to Heavy-Duty Vehicles ................................................................................... 42 3.1 International Truck/Guardian Industries Infrared Reflective Glazing .............................. 42 3.2 Schneider/Freightliner IR Imaging ................................................................................... 44
3.3 Volvo Truck Test .............................................................................................................. 46 3.4 International Truck Test and CFD Analysis ..................................................................... 47 3.5 Sage Electrochromics ........................................................................................................ 48 3.6 New York City Transit Fleet ............................................................................................. 49 4.0 Implementation Barriers ...................................................................................................... 50
5.0 Conclusions and Recommendations .................................................................................... 51 Appendix A. Project Partners .................................................................................................... 54 Appendix B. Chronology and Project Summaries ................................................................... 55

vii

### List of Figures

Figure 1. U.S. air-conditioning fuel use, by state ....................................................................... 3 Figure 2. Normalized compressor power vs. time over the SC03 drive cycle ........................... 4 Figure 3. VSOLE interface ........................................................................................................ 5 Figure 4. Solar radiation model GUI ......................................................................................... 6 Figure 5. Vehicle integrated thermal modeling process ............................................................ 7 Figure 6. Flow path lines from body coolers ............................................................................. 8 Figure 7. CFD mesh of Cadillac STS ........................................................................................ 9 Figure 8. Air temperature contours in a baseline Cadillac STS ................................................. 9 Figure 9. Thermoelectric power output vs. hot-side and cold-side temperature ...................... 11 Figure 10. Required cold-side mass flow vs. hot-side and cold-side temperature ................... 11 Figure 11. Side-by-side Cadillac STS test for the I-MAC program ........................................ 13 Figure 12. Temperature reductions from use of solar-reflective glass in a Cadillac STS ....... 14 Figure 13. Jeep Grand Cherokee ventilation test setup ............................................................ 15 Figure 14. Parked-car ventilation in a Jeep Cherokee ............................................................. 15 Figure 15. Sungate EP and ventilation te mperature reductions in a Cadillac STS .................. 16 Figure 16. Solar-reflective roof temper ature reductions in a Cadillac STS ............................. 17 Figure 17. Solar-reflective shades in a Lincoln Navigator ...................................................... 18 Figure 18. Vehicle Climate Control Laboratory with solar lamps ........................................... 20 Figure 19. ADAM testing a W.E.T. ventilated seat ................................................................. 21 Figure 20. Thermal comfort with the ventilated seat off and on .............................................. 21 Figure 21. Mockup of passenger compartment for testing heat-pipe IP cooling ..................... 23 Figure 22. Temperatures of a heat-pipe-cooled and noncooled IP .......................................... 23 Figure 23. Temperature reductions resulting from heat-pipe cooling ...................................... 24 Figure 24. Traveling-wave thermoacoustic test setup ............................................................. 25 Figure 25. Microchannel regenerator prototype for a thermoacoustic generator ..................... 26 Figure 26. Copper foam heat exchanger for a thermoacoustic system .................................... 27 Figure 27. Bacterial growth from a 10-minute A/C vent outflow ............................................ 28 Figure 28. Fungal growth from a 10-minute A/C vent outflow ............................................... 28 Figure 29. A prototype photo catalytic air-cleaning system ..................................................... 28 Figure 30. Boundary layer capture mockup ............................................................................. 29 Figure 31. ADAM, the ADvanced Automotive Manikin ........................................................ 31 Figure 32. Cross section of a segment of the manikin ............................................................. 31 Figure 33. Physiological m odel finite-element mesh ............................................................... 32 Figure 34. Physiological model de piction of circulatory system ............................................. 33 Figure 35. Thermal comfor t correlation data flow ................................................................... 33 Figure 36. ADAM in a NASA Liquid Cooling Garment ......................................................... 34 Figure 37. ADAM testing an army blanket .............................................................................. 35 Figure 38. Vehicle Climate Control Laboratory ...................................................................... 36 Figure 39. Heads-up thermal sensation a nd comfort voting screen; system in use ................ 37 Figure 40. NREL’s Manikin Environmental Chamber ............................................................ 38 Figure 41. Real-time thermoacoustic data evaluation using an oscilloscope ........................... 39 Figure 42. Standing-wave thermoacoustic prot otype in the Waste Heat Utilization Lab ........ 39 Figure 43. DaimlerChrysler Emissions Test Cell with me tal halide lamps ............................. 40 Figure 44. DaimlerChrysler Environm ental Test Cell with IR lamps ..................................... 41

viiiFigure 45. International Class 6 Series 4300 truck test outside Phoenix, Arizona .................. 43 Figure 46. Cabin breath-level air temperat ure with IRR windshield and sidelights ................ 44 Figure 47. IR imaging test setup at Schneider’s Green Bay facility ........................................ 45 Figure 48. IR image of the baseline and super-insulated truck cabs ........................................ 46 Figure 49. Volvo truck cab test setup ....................................................................................... 46 Figure 50. International truck cab test setup ............................................................................ 47 Figure 51. FMTV geometry ..................................................................................................... 49 Figure 52. Surface mesh of the FMTV .................................................................................... 49 Figure 53. Seasonal variation in mpg fo r hybrid buses shows impact of A/C ......................... 50 Figure 54. Vehicle Ancillary Lo ad Reduction project timeline ............................................... 55



### List of Tables

Table 1. Overview of Solar Reflective Co ating Data from NREL and the Literature ............. 18
Table 2. Results from the Inte rnational Truck Cab Tests ........................................................ 48

ix

### 1.0 Introduction

1.1 History The Vehicle Ancillary Loads Reduction Project fostered a national effort to estimate automotive air-conditioning fuel consumption ra tionally and laid the groundwork for future thermal comfort models. It began as the “C ool Car Project” in 1996 and was first funded internally under a laboratory-directed resear ch and development program at the National Renewable Energy Laboratory (NREL). The firs t two-year project included 19 researchers
from five different NREL research centers focusing on research in transportation technologies, buildings, photovoltaics, wind, basic sciences, and analysis.

With initial funding of $391,468, the project quickly gained industry support. Industry partners such as Chrysler Corporation provi ded a Plymouth Breeze test bed, PPG Industries created several types of solar-reflective glazing for test vehicles, Webasto provided a sunroof, Optical Coating Laboratory Inc. (OCLI) fabricated electrochromic panels for a sunroof, Solarex sent a photovoltaic array for cabin ve ntilation, and Life Enhancement Technologies manufactured heated and cooled seat panels for research. Among the many technologies investigated were these:

• Advanced glazing to reduce the solar load

• Photovoltaics to power a cabin ventilation system in a parked vehicle

• Boundary layer control at windows to capture and exhaust heat (which led to an NREL patent)

• Photocatalytic oxidation to purify cabin air and reduce outsi de air requirements

• Advanced air-conditioning (A/C) concepts, such as ejector systems and desiccant cooling.

This internal project set the st age for a decade of U.S. Department of Energy (DOE) funding totaling $9.16 million. Close collaborations with i ndustry included the test vehicles provided by Chrysler, Ford, and General Motors (GM) . Researchers obtained solar reflective and absorbing glazing from 3M, Guardian Industries, PPG, Solutia, and S outhwall Technologies. Reflecting and absorbing window shades were pr ovided by BOS; climate control seats by Amerigon, Johnson Controls, and W.E.T.; solar reflective films and paint by 3M and PPG; and advanced body insulation by 3M.

Our work focused on light-duty vehicles but led to numerous spin-off projects. These included several Cool Cab projects for Cla ss 8 sleeper cabs. The projects involved DOE, Guardian Industries, International Truck, Vol vo Truck, and Schneider, as well as the U.S. Army, the U.S. Environmental Protection Agency (EPA), the Society of Automotive Engineers (SAE), and the National Aeronautics and Space Administration (NASA).

1.2 Approach Traditionally, the automotive industry has emphasiz ed efficient equipment. Suppliers must be able to assemble the hardware that automotive manufacturers purchase. To reduce the size of this equipment as much as possible, there mu st be an emphasis on reducing thermal loads

1while paying close attention to cost, volume, weight, reliability, and serviceability. Methods for reducing cooling thermal loads can include the following:

• Using reflective glazing, shades, and paint to reflect the infrared (IR) and (or) visible portion of the solar spectrum

• Capturing heat at the vehicle’s boundary through absorbing glass and exhausting it through boundary layer control

• Minimizing conduction into the cabin through body insulation

• Rejecting heat to outside the vehicle using active or passive ventilation of the vehicle’s cabin or through heat pipes while the vehicle is parked in the sun.

In winter, reducing heat loss from the cabin becomes increasingly important in advanced vehicles because waste heat is not always readily available. One example of this occurs when the downsized engine of a hybrid electric vehicle (HEV) is not operating because the vehicle is idling or coasting. Another example occurs when a plug-in hybrid vehicle (PHEV) is operating in all-electric mode. Options to reduce this heat loss include increasing the vehicle body’s insulation or using advanced glazing with a low-emissivity coating or double-glazed
windows.

In addition to having a reduced load, the vehicle mu st be able to warm or cool its occupants as efficiently as possible. Traditional technologie s have been inefficient because they have
conditioned the entire cabin even when ther e is only one occupant. More efficient technologies for single-occupant vehicles could include occupant sensors, body coolers, and
conditioned seats.

Future work must, therefore, involve designing more efficient equipmen t. Whenever possible, waste heat should be used for cooling as well as heating. This can be accomplished through the use of thermoacoustic systems, absorption systems, or adsorption systems, such as those made of metal-hydride. Climate-control equipmen t must be able to operate without using the engine to minimize fuel use. An electric A/C compressor is one option, perhaps one that can operate in heat pump mode to pr ovide heating. Although electric heating can be expensive, it could be an effective technique for direct-d elivery systems, such as heated seats and
windshields.

The options are many, but one of the top challe nges is to meet fuels savings goals while keeping initial and operating costs at reasonable levels. Another challenge is to achieve greater fuel economy while avoiding severa l unintended consequences. For example, polycarbonate glazing can reduce a vehicle’s weight but could cause greater thermal discomfort in winter, because polycarbonate’s long-wave infrared (IR) transmissivity is higher than that of glass. Similarly, more efficient or smaller engines generate less heat to warm cabins than today’s engines do.

Still, the potential is great to reduce fuel use for A/C and increase occupants’ comfort levels at the same time. New technologies are needed that will meet both goals and still be cost effective. The best solutions will probably re quire the development of multiple technologies designed to provide energy-efficient s eating, glazing, and vehicle bodies.

2

### 2.0 Significant Accomplishments

2.1 Modeling

2.1.1 A/C Fuel Use Analysis We calculated the impacts of air-conditioning on fuel use in light-duty vehicles both nationwide and state by state. Our analysis us ed a bottom-up approach to estimate the amount of fuel used annually in vehicles for A/C. Using a thermal comfort model, researchers determined the percentage of time that drivers use A/C to improve their thermal environment.
Environmental conditions were an important input to this mode l. Results for thermal comfort were then combined with statistics concerning when people drive (time of day); where they live (climate, including cloud cover); and how ma ny miles they drive in one year. Finally, vehicle simulations were used to determine the fuel-use penalty associated with using A/C in cars and trucks. This algorithm allowed the resear chers to determine the amount of fuel used for A/C in light-duty vehicles.

The analysis showed that, in 2001, U.S. driv ers used approximately 7.0 billion gallons of gasoline each year to air-condition vehicles. Th is was the equivalent of 5.5% of domestic light-duty vehicle petroleum consumption, or 0.46 million barrels of crude per day, assuming a one-to-one displacement. It took 9.5% of U.S. imported crude oil to produce this much gasoline, assuming a 0.435 refining ratio. 1 Figure 1 shows U.S. A/C fuel use by state.

10 14 19 7

37 78 64

9

187 43

735 179 17

127 15

238 66

109 229 273

61

52 167 22

40 12

219 17

85 144 86

186 21

118

176 95 75 142 242 26

68

68 251

753 76 730

216 86

167

1 7

37 78 64

9

187 43

735 179 17

127 15

238 66

109 229 273

61

52 167 22

40 12

219 17

85 144 86

186 21

118 86

176 95 75 142 242 26

68

68 251

753 19 61

76 730

216 86

167

1 Million Gallons Cooling & Dehumidification

1 to 17
17 to 26
26 to 52
52 to 68
68 to 78
78 to 86
86 to 142
142 to 176
176 to 216
216 to 242
242 to 730
730 to 753

Figure 1. U.S. air-conditioning fuel use, by state

1. Total annual light-duty vehicle fuel use = 125.9 billion gal gasoline, in Ward’s 2001 Automotive Yearbook. Southfield, MI: Ward’s Communications, 2001; importe d oil = 11.1 million barrels per day = 73 billion gal gasoline per year, according to the U.S. Department of Energy’s Energy Information Administration, http://www.iea.doe.gov/cabs/usa.html, accessed April 2001.

32.1.2 Transient A/C Model NREL developed a model that captures all the relevant physics of transient A/C system performance, including two-phase flow effects in the evaporator and condenser, system masseffects, air-side heat transfer on the condenser/evaporator, vehicle speed effects, temperaturedependent properties, and integration with a simplified cabin thermal model. The model was developed within SINDA/FLUINT analysis soft ware environment and integrated with the ADVISOR vehicle systems analysis software first developed at NREL. The SINDA/FLUINT and ADVISOR software employ built-in optimization capabilities that are used to optimize a vehicle’s A/C system within the overall vehicle design optimization process. An example of normalized compressor power output is shown in Figure 2.

Figure 2. Normalized compressor power vs. time over the SC03 drive cycle
Researchers used NREL’s transient A/C system model to perform multi-variable design optimization of electrically-driven compressor A/C systems. Five variables were considered: compressor displacement, capillary diameter, transfer line diameter, condenser tube diameter, and compressor speed. After 83 separate analyses, they determined that the optimum system has a system coefficient of performance (COP) = 3.42 at a co mpressor speed of 700 rpm, a compressor displacement of 120 cm 3 , and an expansion devi ce diameter of 0.191 cm.

The investigation then concentrated on optimizing the system design to maximize the evaporator cooling capacity over the SC03 drive cycle, which measures tailpipe emissions while the A/C is operating at maximum. The CO P of this design was 0.856, far below that of the maximum COP system design. The optimum compressor speed of 2066 rpm and optimum compressor displacement of 276 cm 3 is much higher than that for maximizing COP (700 rpm
and 120 cm 3 , as noted above). This highlights the differences in systems that would be

4required to achieve DOE’s goals to reduce A/C system power requirements in order to reduce vehicle fuel consumption, versus the automo tive industry’s need to maximize cooling capacity and cabin cooldown performance. Clear ly, a systematic methodology that maximizes both COP and evaporator cooling capacity will require dynamic system operation.

We investigated A/C system design optimizations using a two-speed dynamic control strategy to quantify optimized A/C system performance and evaluate compromise A/C system designs that could partially, or s imultaneously, satisfy the two di verse design objectives. A dualcompressor-speed strategy, coupled with the use of an electrically driven compressor, was found to be beneficial in developing syst em designs that improve system COP while maintaining a reasonable evaporator cooling capacity.

2.1.3 VSOLE To better understand solar-reflective glazing and its impact on the heat load of passenger compartments, we developed the Vehicle Solar Load Estimator (VSOLE). VSOLE is a graphical user interface (GUI)-driven tool programmed in the MATLAB environment (see Figure 3). The model calculates solar radiation transmitted, absorbed, and reflected by glazing as a function of the optical properties of the glazing, the glazing’s location, vehicle geometry, vehicle orientation, time, and source of radiation. The model accounts for the angular dependence of the optical proper ties of glass. The program can also display glazing properties and comparisons of different types of glaz ing under the same solar load and vehicle orientation as a function of time. (This software is available from the authors.)

Figure 3. VSOLE interface

5The solar radiation model developed at NREL pr ovides radiation source data for VSOLE. The
data are accessible from within the VSOLE GUI through the “pick a city” option in the radiation-source pull-down menu. The solar ra diation model calculates the solar spectral
irradiance incident on a vehicl e as a function of location, weat her, and vehicle orientation. Weather and sun position data for the model are available for 239 locations in the United States and U.S. territories. An example of the solar radiation model GUI is shown in Figure 4.

Figure 4. Solar radiation model GUI

2.1.4 Integrated Vehicle Thermal Modeling Process We developed the numerical modeling process shown in Figure 5 to assess the impact of reducing the thermal load on A/C system capacity and the amount of vehicle fuel used for A/C. A vehicle’s interior geometry is typicall y defined by computer-aided design (CAD) data or, as is the case for vehicles unde r development, it is not defined.

We followed two approaches to develop a co mputational fluid dynamics (CFD) mesh. One approach was to use a parametr ic modeling tool developed by ICEM CFD to modify a generic vehicle to one with the appropria te dimensions and generate a mesh in preparation for cabin thermal and fluid modeling using CFD software . A second approach was to import the CAD data into BETA CAE Systems ANSA softwa re where it was cleaned up, details were removed, and the surface was meshed.

6CAD

RadTherm

Thermal
Comfort Air Conditioning Cabin
Thermal/Fluid

Vehicle

Fuel Economy Tailpipe
Emissions Occupant
Thermal
Comfort CAD

RadTherm

Thermal
Comfort Air Conditioning Cabin
Thermal/Fluid

Vehicle

Fuel Economy Tailpipe
Emissions Occupant
Thermal
Comfort

Figure 5. Vehicle integrated thermal modeling process

RadTherm was used to model the solar load on the vehicle, convection losses on exterior surfaces, and conduction through the surfaces. FL UENT CFD software was used to model the convective heat transfer and fluid flow in the cabin. We compared the model results with quasi-steady-state vehicle soak data to gain confidence in the model. Before we used the RadTherm software, we used VSOLE to provi de the solar radiati on boundary conditions and
the FLUENT Discrete Ordi nates radiation solver.

We found that excessive run times were needed to achieve a cooldown simulation using the full CFD/RadTherm model. Therefore, a s implified model was created for the cooldown simulations, which used only RadTherm. This simplified RadTherm model was compared
with cooldown data for the vehicle.

Next, the vehicle was simulated using the ADVISOR vehicle simulator to determine the effect
of the reduced A/C load on fuel use. We used two approaches for calculating the A/C power requirement on the engine, depending on the data available. In some cases, we used the
transient A/C model described in section 2.1.2. When only bench data were available, we used a compressor power-versus-rp m curve. For a reduced thermal load case, we reduced the compressor power by the same percent reduc tion as the calculated percent reduction in capacity. We are assuming the reduced thermal load A/C system has the same COP as that of
the baseline case.

We applied the integrated mode ling process to a climate control system proposed by Johnson Controls Inc. The design consists of under-sea t heating and cooling of air for the front and rear passengers and an air recirculation system in the instrument panel (IP). Instead of blowing conditioned air directly on the body, th e system creates an envelope of conditioned

7air around the occupants in the front of the vehicl e. The flow path lines from the CFD analysis are shown in Figure 6.

Figure 6. Flow path lines from body coolers

This distributed heating, ventilating, and ai r-conditioning (HVAC) system improves the driver and front passenger’s comfort le vels compared with those of a baseline vehicle. The overall equivalent homogeneous te mperature (EHT) of the driver was reduced by 1.9°C, while the overall passenger EHT was 1.3°C lower. Since comfort is enhanced, there is potential to use a smaller A/C system compressor while maintaining comfort. Another benefit of a distributed HVAC system is that the passenger side of the sy stem can be turned off if that seat is not occupied. Both actions would reduce A/C fuel use.

As part of SAE’s Improved Mobile Air C onditioning Cooperative Research Program (IMAC), the integrated modeling process was applied to a Cadillac STS vehicle with thermal load-reduction technologies that included solar-r eflective glass, solar-powered parked-car ventilation, and solar-reflective pa int. A combination of these technologies reduced breath air temperature by 12°C (22°F), seat temperatures by 11°C (20°F), the windshield temperature by 20.4°C (37°F), and the instrument panel surface temperature by 16.8°C (30°F). The vehicle simulation showed that reducing the A/C load by 30% resulted in a 26% reduction in A/C fuel use. Figure 7 shows the CFD mesh of the Cadillac STS, and Figure 8 shows the air temperatures in the baseline Cadillac STS.

8Figure 7. CFD mesh of Cadillac STS

Figure 8. Air temperature contours in a baseline Cadillac STS

92.1.5 Integrated Heat Exchanger/Thermoelectric Power Generation Analysis
Tool NREL investigated the use of thermoelectric (TE) devices to capture energy from a vehicle’s waste heat. Researchers developed an integrated heat exchanger/thermoelectric power generation system analysis tool in the MATLAB/Simulink environment. The tool’s capabilities are as follows:

• Simultaneously analyzes heat exchanger and TE device performance

• Optimizes the performance of each to obtain the highest system efficiency and power output

• Outputs the optimum design parameters as a function of hot-side and cold-side temperatures

• Integrated with NREL’s ADVISOR software.

The integrated system analysis approach allowed NREL to simultaneously quantify the effects of important system design parameters on sy stem performance and to maximize power output in a waste heat recovery system. The flexib le TE property input format allowed NREL to analyze segmented-TE and single-TE material designs, including quantum-well and thin-film superlattice TE material designs. The tool was used to investigate potential TE system power output at various locations in th e exhaust streams in light-duty and heavy-duty vehicles for a variety of thermal conditions.

Figure 9 shows the results of a 2-p/2-n segmented-leg TE design analysis. Peak powers of 333, 626, and 843 W are shown for various exhaus t gas flow rates. Figure 10 shows the respective cold-side mass flow required. Power ge neration levels as high as 0.9 kW appear to be possible in light-duty vehicle exhaust flow st reams; power generation levels as high as 6 kW appear to be possible in h eavy-duty vehicle exhaust streams.

The interaction between heat exchanger and TE device performance creates critical system impacts that maximize TE system power outputs and define preferred hot-side and cold-side heat exchanger performance regimes. System power is strongly impacted by interface thermal resistances. Selecting superior TE materials can reduce system cold-side mass flow requirements significantly. Heat exchanger performance requirements to maintain stable TE system operation are much higher in heavy-dut y vehicle exhaust stream applications (by a factor of 15-20) than in light-duty vehicle applications.

10Figure 9. Thermoelectric power output vs. hot-side and cold-side temperature

Figure 10. Required cold-side mass flow vs. hot-side and cold-side temperature

112.2 Vehicle and Component Testing

2.2.1 Solar-Reflective Glazing When a vehicle is parked, typically 50% to 75% of the thermal energy entering the passenger compartment is from transmitted and absorbed solar energy at the glazings. Transmitted energy is primarily absorbed directly by the interior mass. The absorbed energy at the glazing is transferred to the interior by convection and reradiation in the thermal IR wavelength range. Reflecting incident solar radiation at the vehicle glazing is a critical step in achieving significant reductions in thermal loads.

A 3M nonmetallic solar-reflec tive film was soak-tested in two tan Dodge Grand Caravanminivans and two black Ford Explorer sport utility vehicles. The configuration with solarreflective film on all the glazings had the best thermal performance, showing a 1.8°C (3.2°F) reduction in maximum breath temperature. The maximum instrument panel temperature was reduced by 3.4°C (6.1°F) in this case. These re sults were not as good as those for other solarreflective technologies, but an advantage of th e nonmetallic constructi on is that it does not attenuate electromagnetic transmission or recepti on from cell phones and other
communication devices.

NREL and PPG Industries conducted a test prog ram with Sungate laminated solar-reflective glass installed in a Ford Explorer to quantify improvements in fuel economy and reductions in tailpipe emissions. Sungate is a solar-reflective coating consisting of a double stack of silver and dielectric layers. The vehicle with the solar-reflective glazing at all locations had a maximum breath temperature 2.7°C (4.9°F) lower th an that of the baseline vehicle, and the instrument panel was 7.6°C (13.7°F) lower.

NREL later tested a new type of solar-reflec tive glass on a 2005 Cadillac STS as part of the IMAC program. The glass improves reflection of the near-IR portion of the solar spectrum. The test setup is shown in Figure 11.

12Figure 11. Side-by-side Cadillac STS test for the I-MAC program

The Sungate EP allows only 3% of the infrared energy to be transmitted through the glass. Figure 12 shows that this technology at a ll glazing locations reduced the average air temperature by 7.1°C (12.8°F), seat temperatures by 8.7°C (15.7°F), the windshield temperature by 19.3°C (24.7°F), and the inst rument panel surface temperature by 14.6°C (26.3°F). Another way to assess these data is in terms of the maximum possible temperature reduction. The solar-reflective glass in all loca tions reduced the average air temperature by 34% of the maximum possible and the seat temp erature by 35%. Solar-reflective glass also reduces steady-state thermal loads when a vehicle is being driven with A/C on.

130 5 10 15 20 25

Air-Foot Air-Breath Air Dashboard Roof Exterior Front Driver

Seat Front Pass

Seat WindshieldReduction in Temperature (oC) Solar Reflective Glass-all locations

Solar Reflective Windshield-Backlite

Solar Reflective Windshield Solar Reflective Paint-all tests

Figure 12. Temperature reductions from use of solar-reflective glass in a Cadillac STS

In cold environments, solar-reflective glass would also cause the temperature of a vehicle’s
interior to be lower than it would be with traditional glazing. In most of today’s vehicles, drivers are used to a warmer than ambient passenger compartment when the sun is shining
even if it is cold outside. With solar-reflectiv e glazing, drivers will have to adjust their expectations to a cooler interi or in the winter. However, interior temperatures would not be lower than ambient or than those already encountered in a vehicle after sunset.

2.2.2 Parked-Car Ventilation When solar energy does enter the vehicle, it heats the interior mass of the passenger compartment and the air. Venting the warm air and pulling in cooler, ambient air can reduce the temperature of the interior. Therefore, NREL tested various natural and forced parked-car ventilation techniques on a 2000 Jeep Gr and Cherokee (see Figure 13).

14Figure 13. Jeep Grand Cherokee ventilation test setup

The results showed that natural-convection-indu ced flow can be effective with strategically located air inlets and that this technique was nearly as effective as forced convection ventilation with the HVAC blower running on me dium speed. Figure 14 shows that having the sunroof open 6 cm and using floor inlets reduced the cabin’s air temperature by 5.7oC, 38% of the maximum possible temperature re duction, while running the HVAC blower on medium reduced the breath air temperature by 6.9o C. Although having air enter the vehicle at
the foot level enhances natura l convection flow, implementation challenges for this technique include preventing moisture a nd contamination (such as exha ust products, dirt, and animals) from entering the vehicle through the inlets.

30 32 34 36 38 40 42 44 46

Low flow / panel

vents Medium flow / panel

vents Sunroof open 6cm Sidelites open 2cm Sunroof 6cm/double

floorvents Sunroof 6cm/double

floorvents/3 fans

Ventilation TechniqueCabin Air Temperature (C)

Ambient Temperature = 30C Baseline Cabin Air Temperature = 45C, Ambient Temperature = 30C

1.9C
13%

6.9C
46% 2.0C
13% 3.5C
23% 5.7C
38%

7.5C
50%

4.1 watts 81 watts 13 watts

Figure 14. Parked-car ventilation in a Jeep Cherokee

15As part of I-MAC thermal soak testing on the Cadillac STS, we also tested a solar-powered parked-car ventilation system. When air was pulled out of the vehicle, the average air temperature was reduced by 5.6oC and seat temper atures were reduced by 5o-6oC. These were 26% and 21% of the maximum possible temperature reductions, respectively. Air was pulled in through the HVAC heater/defroster ducts and natural vehicle body leakage areas. Even though they do not reduce temperatures as mu ch as solar-reflective glass does, parked-car ventilation technologies can be used in conjunction with so lar-reflective technologies to reduce interior temperatures significantly. Co mbining these technologies in the Cadillac STS reduced the average air temperature by 46% and the seat temperature by 44% of the maximum possible. The temperature reductions for the Sungate EP in all glazing locations and for solar-powered ventilation are shown in Figure 15.

Figure 15. Sungate EP and ventilation temperature reductions in a Cadillac STS

.2.3 Solar-Reflective Opaque Surface Coatings interior surfaces, the resulting

n

s on

e used two identical vehicles: one baseline a nd the other modified. A visibly reflecting roof

etermine

s part of the I-MAC project, we soak-tested a solar-reflective film on the roof of a stationary 5.6 12.0

8.8 16.8

6.0 10.3 11.9 20.4

0 5 10 15 20 25

Air-Foot Air-Breath Air Dashboard Roof Exterior Front Driver
Seat Front Pass
Seat WindshieldReduction in Temperature (oC)

0 9 18 27 36 45Reduction in Temperature (oF)

2 If the exterior vehicle skin temperature is warmer than the
conduction heat transfer will warm the vehicle’s interior. This is more likely to occur whe solar-reflective glazing and (or) parked-car ven tilation are used and the interior is cooler. Using a 2001 Lincoln Navigator, NREL investigated the impact of solar-reflective coating interior cabin temperatures on a parked vehicle.

W film from 3M reduced breath air temperature by 12% of the maximum possible temperature reduction, which is defined as the differen ce between the baseline vehicle breath air temperature and ambient. The exterior surfaces were covered with aluminum foil to d the largest potential reduction. The breath air temperature was reduced 28% relative to the maximum possible reduction for this case.

A
Cadillac STS in 2005. The film was an infrared reflecting product (CI-100T) manufactured by 3M. The baseline gray paint had a solar absorp tance of 0.78, and the paint with the film had a

16solar absorptance of 0.55. The 6.7oC cooler roof temperature resulted in less than a 1oC reduction in the breath air temperature (Figure 16).

In the summer of 2006, we tested a prototype solar-reflective paint on the Cadillac STS. The

uld

s new baseline paint had a solar absorptance of 0.89, and the solar-reflective paint had a solar absorptance of 0.82. The exterior surface temp erature was 6.0oC cooler than that of the baseline. The impact of paint by itself was not tested, but we estimate that the results wo
have been similar to the 2005 data. Table 1 summar izes NREL solar reflective coating data a
well as data in the literature.

0.5 1.2

0.8 0.9 6.7

0.4 0.4

-0.6 -1 0 1 2 3 4 5 6 7 8

Air-Foot Air-Breath Air Dashboard Roof Exterior Front Driver

Seat Front Pass
Seat WindshieldReduction in Temperature (oC)

Figure 16. Solar-reflective roof temp erature reductions in a Cadillac STS

hile vehicle skin temperatures can be signif icantly reduced with these technologies, the

, the W impact on interior temperatures is not that large because 1) the majority of thermal load is entering though the windows, 2) the roof is typically insulated, and 3) wind reduces the advantage of the lower temperature skin by coo ling the hot skin. If the vehicle is moving
increased convective heat loss further reduces the thermal impact of the solar-reflective coatings on opaque surfaces.

17Table 1. Overview of Solar Reflective Coating Data from NREL and the Literature

Vehicle Source Test Configuration absorptance

baseline absorptance

reflective coating exterior surface temeprature reduction ( C) breath air temeprature reduction ( C) Comments

Ford Explorer NREL internal test data black vs white vehicle est. 0.96 est. 0.4 -20 -2.1

Lincoln Navigator NREL VTMS8 paper, 20- 24, May 2007, Nottingham, UK red vs aluminum foil est. 0.7 est. 0.15 -5.6 Used foil to assess the maximum possible roof temperature reduction

full sized SUV Ford SAE paper 2005-
01-1880 black vs solar reflective

black 0.95 0.75 -2.7 A ssumed breath temperature, location not clearly stated in paper

full sized SUV Ford SAE paper 2005-

01-1881 red vs solar reflective

red 0.78 0.64 -1.3 A ssumed breath temperature, location not clearly stated in paper

full sized SUV Ford SAE paper 2005-
01-1882 black vs white 0.95 0.5 -4.6 Assumed breath temperature, location not clearly stated in paper

Cadillac STS NREL SAE paper 2007-
01-1194 Metallic silver vs 3M
solar reflective film over

silver 0.79 0.55 -6.7 -1.2 film on roof only

Cadillac STS I-MAC final report Baseline gray paint vs PPG solar reflective gray paint 0.89 0.82 -6 paint not tested by itself, no data for breath air

B Class vehicle Ihara presentation, IEA Workshop "Cooling Cars with Less Fuel", Oct 24,
2006 dark blue mica vs solar
reflective dark blue mica not reported reduction of .04

to .44 -5 to -10 -1.6 to -3.9 Unclear what is meant by "anterior heading compartments", assumed breath for now

2.2.4 Window Shades NREL assessed the impact of the use of window shades in the 2001 Lincoln Navigator thermal soak test program. Reflective shades manufactured by BOS were placed inside the cabin against the windows (Figure 17). Hooks near the windows held them in place, and a small air gap separated the shades from th e windows. The reflective shades on all windows showed a temperature reduction of roughly 20 % of the maximum possible reduction, based on the difference between the baseline vehicle’s average air temperature and ambient. The upper instrument panel showed a reduction of 43%. Black shades manufactured by BOS were also tested in the Navigators. The average cabin air temperature increased in comparison to that of the baseline vehicle. Even though the shades block transmitted radiation, their higher temperature along with convection to the air in the cabin caused a net heat gain in the cabin.

Figure 17. Solar-reflective shades in a Lincoln Navigator

As part of the I-MAC project, we soak-teste d a common, manually installed reflective shade
behind the windshield and backlite of a stati onary Cadillac STS in 2005. Although the test day was not completely cloudless, we were ab le to measure impacts during sunny periods.

18The IP and breath air temperatures were reduced by 25oC and 4oC, respectively. The seat temperatures were reduced 5oC, while th e windshield temperature increased 8oC.

Exterior mounted shades would be better than interior shades, but durability concerns are a barrier. Using shades would eliminate the need for solar reflective glass to reduce the solar load during a soak. However, reducing the solar load while the A/C is operating would improve comfort and reduce steady-state A/C fuel use. Note that using interior shades results
in a hotter window after a soak and dur ing the initial phase of a cooldown.

One technology that could be particularly beneficial is switchable, diffusely reflecting glazing. We are not aware of a functional prot otype in existence, but some suppliers are conducting research in this area. In theory, it would work as follows: the car is parked in the sun and the glazing is activated to park mode, becoming reflecting. When the driver returns, the glazing goes back to its driving state. The power required would have to be low to allow for long periods of time when the vehicle is parked, and a fail-clear logic would be needed to mitigate safety concerns.

2.2.5 Insulation The benefit of headliner insulation depends on exterior surfaces and interior temperatures. If the interior is warmer than the exterior, then increasing the insulation in the headliner will make the car warmer. However, if solar-reflective glazing and (or) parked-car ventilation are used to cool the car, headliner insulation may reduce the heat gain of a parked car.

A CFD analysis of a Jeep Grand Cherokee resulted in only a 0.2oC reduction in the average cabin air temperature due to the insulation in the roof. Advanced technology insulation on the roof of the Lincoln Navigator reduced the cabin breath air temperature by 5% of the maximum possible. In a Cadillac STS, adding insulation based on today’s technology had little impact on interior soak temperatures.

Insulation was not very effective in reducing parked-car thermal loads in conventional
vehicles. If the thermal loads are reduced fi rst with solar-reflective glass or ventilation,
insulation could become more im portant. When the A/C of a vehicle in use is operating in a warm outdoor environment (e.g., in summer), added insulation would reduce thermal loads. In winter, when the interior is warm and the out door environment is cold, insulation would help to reduce the heating load. In the United States , cabin heating is not an issue with today’s vehicles because waste heat is available. But this will be a challenge for advanced vehicles and small diesels that have less (or no) waste heat available to warm the cabin.

2.2.6 Climate-Control and Low-Mass Seats Increasing delivery efficiency means providing climate control more effectively to each vehicle occupant, thereby increasing thermal comfort with a net decrease in energy consumption. Automotive seats have the potential to improve delivery efficiency because of their large contact area with, and proximity to, occupants. A standard automotive seat thermally insulates the occupa nt and reduces evaporative c ooling of perspiration, thus increasing the occupant/seat contact temperature. Both actively ventilated seats and meshed

19seats are potentially low-energy approaches to improving both thermal comfort and climate control delivery efficiency.

The NREL Vehicle Climate Control Laboratory was developed to simulate thermal soaking and cooldown of a vehicle passenger compartme nt (Figure 18). A compact car passenger compartment was thermally soaked for 3.5 hours using a 963 W/m 2 ± 23% full spectrum solar simulator. The average room environment was controlled to 31.6°C ± 0.4°C and 30% ± 5% relative humidity. Both the ADvanced Au tomotive Manikin (ADAM), which will be discussed in a later section, and human subjects were first conditioned in an office environment. ADAM (see Figure 19) and a subj ect then entered the heat-soaked room, and the subject stood for 30 seconds before doing step exercises for 1 minute. The cooldown began 45 seconds after cabin entry, allowing time for pre-cooldown evaluations to be made.

Figure 18. Vehicle Climate Control Laboratory with solar lamps

ADAM was also used to test ventilated seat s provided by W.E.T. Automotive Systems.
ADAM recorded a seat c ontact temperature reduction of ~4.7° C when the ventilated seat was
on and an increase in heat loss from the back and the bottom of ~60 W/m 2 when the ventilated seat was on in comparison to when it was off. This resulted in an overall thermal sensation improvement of 0.28 (on a +4 to -4 scale where positive values indicate that one is feeling hot, and negative values indicate that one is f eeling cold.). The average evaluation of thermal comfort over the cooldown is shown in Figure 20. We estimate that using ventilated seats could allow the A/C system capacity to be reduced by 7%. NREL’s A/C fuel use model
indicated this could result in an estimated 522 million gallon/year reduction (7.5%) in U.S.
A/C fuel use.

20Figure 19. ADAM testing a W.E.T. ventilated seat

-3 -2 -1 0 1 2 3

-5 0 5 10 15 20 25 30 35 40 Cooldown Time (min)Thermal Comfort

Seat Off

Seat OnIncreasing ComfortDecreasing Comfort Seat on, improved comfort

A/C Start

Figure 20. Thermal comfort with the ventilated seat off and on

21A prototype seat with a meshed back was al so tested, with encouraging results. Using a reduced, 96% heat capacity A/C system, we observed an average seat back and bottom temperature reduction of 4° and 0.6°C, respec tively. Assuming that using a meshed bottom would provide results similar to those for the meshed back, much of the thermal benefit gained through ventilation could be achieved using low-mass meshed seats, and energy costs would not increase. One disadvantage of mesh seats, however, is that they increase body cooling during cold-weather driving. Traditional seats insulate the back, but a low-mass seat would cause heat loss from the back during wi nter. Occupants might find this heat loss uncomfortable, especially if they are expecting an insulated seat. So, the lack of thermal control, physical ergonomics, and safety ar e some remaining challenges for mesh seat technologies.

2.2.7 Instrument Panel Heat Pipe Cooling When a vehicle is parked, the instrument pane l can absorb a large amount of heat, attain temperatures approaching 100oC, and impact drivers’ thermal comfort and cooldown performance. Researchers constructed a mock-up of a passenger compar tment and instrument panel to assess the impact of us ing heat pipes to cool the instrument panel (Figure 21). Experimental results demonstrated IP surface temperature reductions of 20° to 30°C during maximum solar intensity envi ronments of 525 to 800 W/m 2 (which are typical of Golden, Colorado, from January to April), in comparison to un-cooled conditions.

The heat pipe’s cooling effect in the IP also reduced windshield temperatures by 9° to 12°C compared with those of the non-cooled configur ation in the April 2001 testing. A cooler IP and windshield would significantly improve the th ermal comfort of the driver and passengers in a typical vehicle cabin. In addition, Figu re 22 shows how IP cooling reduced cabin air temperature by 4° to 10°C during long-term vehicle thermal soak conditions in these tests. Figure 23 provides a summary of the temper ature reductions for the various tests.

Freeze/thaw tests were also conducted on the heat pipe systems in the IP cooling demonstration at NREL. All the heat pipes surv ived the freezing event, and all but one heat pipe demonstrated the ability to start up and operate normally in both an evaporator-led and a condenser-led thaw process. Besides having lower surface temperatures, the electronic components in the IP would also benefit from th e lower temperatures as well as the reduced heat pickup of the airflow in the A/C ducts. Howe ver, there are barriers to incorporating heat pipes in the IP. These include the need for incr eased mass, volume, and cost for the pipes as well as the best place to locate the condensing section outside the cabin.

22Figure 21. Mockup of passenger compartment for testing heat-pipe IP cooling

Figure 22. Temperatures of a heat-pipe-cooled and non-cooled IP

23T e m p e r a t u r e D i f f e r e n t i a l F r o m

T e m p e r a t u r e D i f f e r e n t i a l F r o m

H e a t P i p e C o o l i n g [

H e a t P i p e C o o l i n g [ ° C ]

0 5 10 15 20 25 30

Jan. 01 Jan. 01 Feb. 01 April. 01 Breath

IP

Windshield

0 5 10 15 20 25 30

Jan. 01 Jan. 01 Feb. 01 April. 01 Breath

IP

Windshield

Figure 23. Temperature reductions resulting from heat-pipe cooling

2.2.8 Waste Heat Utilization: Thermoacoustics Thermoacoustics is an innovative technology that uses sound to provide cooling or produce electricity. Thermoacoustic eff ects, which convert heat energy to sound, have been well understood for more than 100 years. However, substantial design imp rovements been made only over the past two decades in regard to th ermoacoustic engines and refrigeration cycles. Recently, thermoacoustic refrigerators have flow n on the space shuttle, cooled electronics in a U.S. Navy destroyer, and cooled Ben and Jerry’s ice cream.

Thermoacoustics has many potential advantages over a conventional A/C system to cool a vehicle cabin. For example, it uses waste heat, is reliable and inexpensive, does not place an extra energy load on the engine, relies on ga ses that are environmentally benign, has no moving parts (thus a device should last a long time), and requires no lubrication. The downside is that, because of its low energy density, a thermoacoustic device could take up significant volume. If we can overcome that barrier, it could be one of the cooling technologies in your next-generation car.

During the last quarter of 2004, NREL de signed and developed a standing-wave thermoacoustic device that pumps heat using a st anding sound wave to take the working fluid (helium) through a thermodynamic cycle. We relied on the heating and cooling that accompany the compression and expansion of a gas in a sound wave to produce cooling for
the interior of a vehicle. The device was modular and allowed di fferent stack designs and heat exchangers to be used in order to assess the most cost-efficient and best-performing
components.

Modeling showed that a thermoacoustic standi ng-wave engine and heat pump has a heat efficiency of approximately 15% and a heat pump COP of approximately 1. An NREL research team finished testing a standing-wav e thermoacoustic engine and heat pump in early

242005. The thermoacoustic engine performed within 10% of the modeled results. However, the heat pump provided only 20 W of cooling. Th e poor performance of the heat pump was attributed to combining the room temperature heat exchanger for both the engine and heat pump into a single unit. Researchers determined that the pressure wave from the engine has to be fully developed before it can be used in c ooling. This problem can be rectified easily by separating the heat engine from the heat pump and incorporating two ambient heat exchangers. Although the standing-wave thermoac oustic system works, it has to be too large to generate sufficient cooling power for a light-duty vehicle. Therefore, NREL researchers concentrated their efforts on developing a sm aller, traveling-wave thermoacoustic system.

In 2006, the NREL team assembled and tested a traveling-wave thermoacoustic engine (Figure 24). Like the standing-wave prototyp e, the traveling-wave system was modular, allowing different components (such as heat ex changers and regenerators) to be tested. We were particularly interested in testing a microchannel regenerator and copper foam heat exchanger.

Figure 24. Traveling-wave thermoacoustic test setup

The regenerator is an important component in a traveling-wave system because it amplifies the sound. Our modeling indicated that the mic rochannel regenerator would approximately double the total acoustic power output and increas e the conversion efficiency of heat to acoustic power by 15% in comparison to traditi onal wire mesh regenerators. Figure 25 shows a microchannel regenerator with rectangular flow passages measuring 1 mm by 0.075 mm. This microchannel regenerator did not perform as expected, however. Rather than reducing viscous losses, the soldering technique and the method used to trim the shims increased the viscous losses in the regenerator. Furthermor e, the spacing between plates within the regenerator was uneven, which led to further losses in efficiency.

25Figure 25. Microchannel regenerator prototype for a thermoacoustic generator

The copper foam heat exchanger shown in Figure 26 was used in hope of eliminating the
hundreds of welds used in traditional shell-a nd-tube heat exchangers for thermoacoustic systems. The copper foam heat exchanger design also eliminated the need for penetrations into the pressure vessel. Inst ead, it relied on heat conduction thr ough the pressure vessel walls and the copper foam to exchange the hot vehicl e exhaust gas with the thermoacoustic working
fluid.

Unfortunately, there was a very large temperat ure difference across the surface of the copper foam heat exchanger. That la rge temperature difference resulte d in non-uniform amplification of the incoming sound. It also has the potential to cause jet or convectiv e streaming, reducing the overall efficiency of the thermoacoustic device.

26Figure 26. Copper foam heat exchanger for a thermoacoustic system

NREL researchers determined from the modeling and test results that a traveling-wave thermoacoustic system for direct vehicle cooling will not be viable for light-duty vehicles because the resonant cavity needed is too large. To decrease the cavity’s size, a new combination of gases and working fluid is needed that will lower the resonant frequency of the device without reducing the power-per-unit volume.

One way to reduce the length of the resonant cav ity is to combine a heavier gas with a lighter gas. Unfortunately, combining gases precipitous ly reduces the power-per-unit volume, and the result is an unrealistically large device diameter to provide the cooling needed. However, we determined that a traveling-wave thermoacoustic system could in fact be used in light-duty
vehicles for electri city generation. Electrical power coul d be produced through the use of a flexible membrane, which would also determine the resonant fr equency of the thermoacoustic system and, therefore, its size. Future work s hould focus on reducing the cyclical fatigue of such a membrane for eventual integration into light-duty vehicles.

2.2.9 Indoor Air Quality After reducing the peak thermal load and solar gain, the next most important approach to minimizing A/C loads is to reduce the amount of outside air brought in for ventilation. It is
more effective to condition recirculated cabin ai r than to treat very hot air brought in from outside (or very cold air in the case of cabin heating). Increasing the recirculation of air leads to two additional challenges: (1) removing odors, bioaerosols, and harmful volatile organic compounds (VOCs), and (2) controlling humidit y levels to avoid condensation on cold
surfaces found when the vehicle is either in he ating mode (e.g., cold windows) or in cooling mode (e.g., cooled seats, pipes, or ducts). In addition, a microbial examination of the A/C system of a 1996 Chevrolet Lumina provided an example of what comes out of a vehicle’s vents. Figure 27 shows the resulting bacterial growth and Figure 28 shows the fungal growth
that occurred after a 10-minute exposure to the A/C vent flow.

27Figure 27. Bacterial growth from a 10-minute A/C vent outflow

Figure 28. Fungal growth from a 10-minute A/C vent outflow

Techniques such as photocatalytic oxidation (PCO) can reduce VOCs and odors in a vehicle’s
cabin. NREL’s PCO device uses a room-temperature, low-pressure-drop process that traps
and oxidizes VOCs and bioaerosols in the vehi cle. The system, shown in Figure 29, operates with ultraviolet light and a titanium dioxide catalyst. It is inexpensive and requires minimal maintenance. We measured significant reductions in formaldehyde, acetaldehyde, and acetone while testing this device.

Figure 29. A prototype photocatalytic air-cleaning system

282.2.10 Boundary Layer Capture Section 2.2.4 described the Lincoln Navigator test data that showed interior window shades can trap warm air and result in warmer cabin ai r temperatures. One way to avoid this situation is to vent the warm air layer between the window and shade. Small fans were integrated with low-flow exhaust plenums to extract therma l boundary layers from window shading devices. A mockup of a boundary layer capture system is shown in Figure 30. We found that boundary layer thermal control required about 0.8 L/s pe r linear meter (0.5 cfm per linear foot) of window. Because of the increased temperature of the boundary layer relative to the bulk air temperature in the vehicle, we found that boundary layer control required 30% to 50% less airflow than strategies that ventilate the entire interior of the vehicle. Removing hot boundary layers is more effective than letting heat mix within the vehicle and then trying to bulkventilate the entire interior.

Figure 30. Boundary layer capture mockup

2.2.11 Electrochromic Sunroof
An electrochromic window is an example of a shading technology that is built into the glazing. We built an electrochromic sunroof using samples from OCLI. The transmissivity of electrochromic glazing can be controlled to be cl ear, opaque, or partiall y clear with separate driver and passenger controls to adjust solar ga ins while the vehicle is parked or being driven. Electrochromic windows, which chan ge transmissivity with an applied voltage of as little as 2 V and only a few milliwatts, can be made in various colors. In principle, electrochromic windows can be applied to the side glazing a nd backlite to control solar gains, match a vehicle’s color for aesthetic purposes, and enha nce security. Photovoltaics can be integrated into the electrochromic window to provide power needed to change the state of the window.

292.3 Thermal Comfort Tools

NREL developed a suite of ther mal comfort tools to help develop smaller and more efficient climate control systems in automobiles. These tools consist of the thermal comfort manikin described earlier, a physiological model, and a psychological model linked together to assess comfort in a transient, nonhomogeneous envir onment. The manikin and models have been validated by comparison with physiological data that are available in the literature and with test subject data used to de velop the psychological model.

The integrated human thermal comfort system consists of a thermal manikin controlled by a finite-element physiological model of the hum an body. The thermal manikin is a surface
sensor that measures the rate of heat loss at 120 independently controlled zones. The skin heat transfer rates are sent to the physiological model, which computes the skin and internal temperature distribution and surface sweat rates. This information is then sent back to the manikin, which generates the prescribed skin te mperatures, surface sweat rates, and breathing rates. As the model steps forward in time, this loop provides a transient measurement tool. The psychological comfort model uses temperat ure data from the physiological model to predict local and global thermal comfort as a function of local skin and core temperatures and their rates of change. Using this manikin as a sensor simplifies the complexities of heat transfer from clothing and the environment into local heat loss measurements from the skin.

2.3.1 ADvanced Automotive Manikin The thermal manikin is approximately 175 cm tall and was sized to represent dimensions of a western person in the 50th percentile (Figure 31). ADAM weighs approximately 61 kg, which is heavy enough to compress an automotive seat and provide a realistic contact area. The manikin’s skeleton is composed of laminated carbon fiber, which supports its structure, houses all internal components, and provide s mounting locations for surface zones.

The manikin’s fundamental components are the 126 individual surface segments, each with a typical surface area of 120 cm 2 . Each segment (Figure 32) is a stand-alone device with integrated heating, temperature sensing, sweat distribution and dispensing , a heat flux gauge, and a local controller to manage the closed -loop operation of the zone. The high thermal conductivity of the all- metal sweating surface increases thermal uniformity and speed of response. A high-porosity layer within the su rface provides lateral sweat distribution, while the lower porosity of the exterior promot es uniform sweat across the surface.

Distributed resistance wi re provides uniform heating across the zone surface. Six segments are controlled in pairs, for 120 se parately controlled zones. A sing le zone controller, including flow control, is mounted directly on the back of each segment. The skin temperature of each zone is determined by an array of thermistors (typically, four) on each zone. A heat flux gauge integrated onto the internal surface of each zone measures heat transfer between the surface zones and the internal body cavity.

30Figure 31. ADAM, the ADvanced Automotive Manikin

Figure 32. Cross section of a segment of the manikin

31ADAM was built by Measurement Technology Northwest, Seattle, Washington. The
characteristics that make ADAM a uni que thermal manikin are as follows:

• High spatial resolution (120 zones)

• Self-contained

• Uniform sweating and heating over the entire area of the manikin

• Finite-element physiological model control.

2.3.2 Human Thermal Physiological ModelThe NREL Human Thermal Physiological Model is a three-dimensional transient finiteelement model of the human body. The model simulates human internal thermal physiological systems, such as muscles, blood, and thermore gulatory responses. The model was developed using ANSYS commercially available finite-element software. This software computes heat flow by conduction, convection, a nd mass transport of blood. The arms and legs consist of bone, muscle, fat, and skin. Ther e are additional lung and abdominal tissues in the torso and brain tissues in the head. The finite element mesh is shown in Figure 33.

Blood flow is modeled with a network of suppl y and return pipe elements within each body zone (Figure 34). The diameter of the pipes d ecreases from the center of each zone outward, toward the skin and extremities. The thermoregulatory system controls physiological responses, such as vasoconstriction/dilation, sw eating, shivering, and metabolic changes.

Figure 33. Physiological model finite-element mesh

32Figure 34. Physiological model depiction of circulatory system

2.3.3 Human Thermal Comfort Empirical Model Under a subcontract to NREL, a researcher at the University of California, Berkeley, performed 109 human subject tests in its Cont rolled Environmental Chamber under a range of steady-state and transient thermal conditions. The tests were conducted to explore the relationship between local thermal conditions and the perception of local and overall thermal comfort. Core and local skin temperature data and subjective data we re used to develop a predictive model of thermal se nsation and perception. The rela tionship between the model’s inputs and outputs is shown in Figure 35.

The researcher concluded that overall comfort is not an additive function of all local perceptions but is instead “complaint”-driven. This means that the most uncomfortable body parts drive the overall perception of thermal comfort. However, we encountered some difficulties in using this approach. Using the data available, we found a straight average to be a better predictor of subjective responses.

Physiology

T skin,local , T skin,mean , T

core Physiology

T skin,local , T skin,mean , T

core

Local Thermal
Sensation: S l Local Thermal
Sensation: S l

Overall Thermal

Sensation: S

o Overall Thermal

Sensation: S

o Local Thermal
Comfort: C l Local Thermal

Comfort: C l

Overall Thermal
Comfort: C

o Overall Thermal
Comfort: C

o

Figure 35. Thermal comfort correlation data flow

2.3.4 Nonautomotive Applications for Thermal Comfort Tools NASA currently uses liquid cooling garments (L CGs) under spacesuits to remove heat from the human body during a spacewalk. Thermally c onditioned liquid is circulated through small

33tubes distributed around the suit. We used ADAM to assess a Shuttle LCG (Figure 36) as well as an Orlan LCG, a Russian-designed coolin g garment. NASA uses a comfort curve to determine the inlet flow temperature as a function of metabolic rate for the Shuttle LCG. We tested three points on the curve and two points off the curve.

Figure 36. ADAM in a NASA Liquid Cooling Garment

The core temperature for the Orlan LCG was an average of 0.06oC lower than that of the Shuttle LCG in all tests. Since the sweat rate is a function of core temperature in the model,
the Orlan LCG also had lower sweat rates. Heat transfer to the LCG fluid was, on average, 15 W greater for the Orlan suit, indicating better heat transfer in comparison to that of the Shuttle
LCG. This resulted in lower core and skin te mperatures. The less-than-perfect fit on the upper back of the Shuttle LCG prevented a good co mparison of thermal se nsation and comfort.

Constant skin temperature tests showed that sweat impacts the performance of LCGs through increased thermal conductivity resulting from mo isture between the skin and the tubes and condensation on the tubes. A comparison of skin temperatures from a model control run with NASA subject data showed reasonably good correlation. ADAM may ha ve overestimated the leg temperature because he did not walk like the subjects did.

34We also used NREL’s thermal comfort tools to assess technologies to maintain the thermal state of a patient during a medical evacuation, as part of a test program funded by the U.S. Army Aeromedical Research Laboratory (USAAR L). Injured persons arriving at a field hospital may be hypothermic. E nvironmental conditions during me dical transport, along with a traumatic injury, can make it difficult for human bodies to maintain thermal balance. We
used our thermal manikin and Manikin Envir onmental Chamber to evaluate current and proposed thermal blankets to reduce or preven t hypothermia in patients during transport.

A wool blanket was used as the baseline, and the manikin was controlled with the physiological model (Figure 37). The electrical and chemical blankets generally resulted in warmer skin and core temperatures, although one of the electric blanket configurations resulted in a lower core temperature. This demonstrates the value of testing using a manikin and the risk of assuming that even an expensive electric blanket will reduce heat loss. With constant temperature control, using a chemical bl anket with a radiation shield wrap resulted in the lowest heat loss. The electric blanket with the lower core temperature had a correspondingly higher heat loss compared with that of the wool blanket. Supplemental testing showed that heat loss can be significan tly reduced in any configuration by placing a
wool blanket between the patient and the mesh stretcher.

Figure 37. ADAM testing an army blanket

2.4 Test Facilities

2.4.1 Vehicle Climate Control Laboratory The Vehicle Climate Control Laboratory (VCCL) at NREL was developed to simulate the thermal soak and cooldown of a vehicle passe nger compartment. The test setup shown in

35Figure 38 consisted of a compact car passenger compartment from A to C pillar, and an automobile A/C system. Environmental conditi ons were supplied by a full-spectrum solar simulator and room temperature and humidity control. The VCCL was used to assess the thermal comfort and fuel-use impacts of climate control seats (Section 2.2.6)

Figure 38. Vehicle Climate Control Laboratory

The solar simulator, “a” in Figure 38, had a mean irradiance of 963 W/m 2 ± 23%. Metal halide lamps were used to approximate the solar spectrum. The front of the car was illuminated because it was the area of primary in terest in this study. Collimation of the light was not addressed because the simulator’s primary purpose was thermal loading.

Air-conditioning was simulated using an actual system with a belt driven by an electric motor, “b” in Figure 38. The change in the thermodyna mic state was measured across the air side of the evaporator to allow calculations of heat removal to be made. To prevent the evaporator from overcooling or freezing, researchers used dead-band control of the evaporator’s exit temperature. This resulted in an average steady-state vent exit temperature.

A wind-flow simulator, “d” in Figure 38, wa s designed and built to blow air across the windshield and correct for the overheating resulting from the lack of reradiation and ambient
air movement.

The temperatures in the test setup were taken at more than 80 locations, measuring both room and passenger cabin conditions. Concentric cylin der radiation shields were used to measure passenger compartment air temperatures.

36To simplify the recording of a subject’s evaluation of thermal comfort, the Vehicle Ancillary Load Reduction (VALR) team built a heads-up voting and driving simulation interface (Figure 39). This enabled computer aided data acquisition of votes on thermal comfort while improving accuracy and reducing data entry time. When prompted, the subjects selected their thermal sensation and comfort level by changing the position of the steering wheel; they recorded their votes by toggling the headlight high beam lever. The interface improved thermal comfort testing by using a driving simulation between voting periods to maintain a
realistic metabolism and keep the evaluator’s attention.

Figure 39. Heads-up thermal sensation and comfort voting screen; system in use

2.4.2 Manikin Environmental Chamber The Manikin Environmental Chamber provides a controlled environment for preconditioning
ADAM for tests inside the VCCL. The chamber was also used for calibration and validation tests for ADAM and for tests of a liquid coolin g garment with NASA and of a thermal blanket with the U.S. Army (Section 2.3.4).

Measuring approximately 2.5 m by 2.5 m, the room shown in Figure 40 has a dedicated HVAC system installed to provide humidity, te mperature control, and air recirculation. The windows, walls, and floor are insulated to reduc e heat transfer to surrounding rooms. The control system maintains temperatures be tween 15°C and 38°C. The humidity can be controlled between appr oximately 20% and 100% , depending on the room temperature set points. A portable dehumidifier is available when high humidity in the building makes it difficult to achieve lower humidity levels. Typical airflow velocity in the middle of the room where the manikin is positioned is approximately 0.1 m/s. Portable fans are used to provide higher air flows when desired.

Relative humidity can be controlled to ±1%, a nd temperature surveys have shown variations of less than 0.4°C from floor to ceiling in the center of the room. The air temperature is measured with type K thermocouples located at head, waist, and foot le vel. The wall, ceiling, and floor temperature are also measured. A Neslab water chiller was installed to provide a
source of chilled water to the chamber.

37Figure 40. NREL’s Manikin Environmental Chamber

2.4.3 Waste Heat Utilization Laboratory NREL’s Waste Heat Utilization laboratory hous es thermoacoustic component development, a high-vacuum capability, cryogenic tank development, and hydride and getter evaluations. The equipment for the lab is as follows:

• High-vacuum hardware

• Helium leak detection

• Signal processing

• Acoustic system analysis (see Figure 41).

In this laboratory, we have demonstrated an ammonia/water absorption cycle, a thermoelectric cooling demonstration unit, a desiccant c ooling loop, a heat-driven standing-wave thermoacoustic cooler (Figure 42), and a traveling-wave thermo acoustic prototype.

38Figure 41. Real-time thermoacoustic da ta evaluation using an oscilloscope

Figure 42. Standing-wave thermoacoustic prototype in the Waste Heat Utilization Lab

392.4.4 Outdoor Testing
NREL researchers have conducte d outdoor tests of advanced t echnologies in vehicles to investigate reducing solar loads and possibly th e size of vehicle mobile air-conditioning systems (MACS). A typical thermal soak test co nsists of two vehicles and a central data acquisition system (Figure 11). We have acce ss to high-quality weather data from NREL’s Solar Radiation Research Laboratory.

For one test program, we gathered a large bod y of data on a Jeep Grand Cherokee (Figure 13). We then tested the vehicle in two Chrysler test cells, one with metal halide lamps (Figure 43) and one with IR lamps (Figure 44) to find out if a vehicle must be tested outside or if indoor tests using solar lamps can be used to accurately simulate the sun.

Figure 43. Chrysler Emissions Test Cell with metal halide lamps

40Figure 44. Chrysler Environmen tal Test Cell with IR lamps

Steady-state vehicle thermal soak tests were performed indoors using data from actual outdoor test conditions. Vehicle temperature meas urements from indoor test cells were then compared with measurements taken outdoors. Indoor test results show that the windshield was
3.4°C cooler and the IP was 4.8°C cooler when metal halide lamps were used. In addition, the driver’s seat was 1.4°C cooler and the roof was 20.1°C hotter. Trim temperatures were approximately the same.

The differences were thought to be caused by the use of a large array of lamps (a planar source) versus the sun (a point source). Specifi cally, in an outdoor test, the roof exchanges radiant heat energy with the cool sky; in the test cell, it exchanges radiation with hot lamp bulbs and the associated structure. In the outdoor test, the location of the sun and the vehicle’s geometry determine the solar radiation in cident on each window. Some windows are completely shaded from incident solar radia tion because of the position of the sun. In the indoor test, using the overhead planar lamp arra y results in a different amount of incident radiation on all the windows, even though the global horizontal flux on the hood matches that
of the outdoor test.

The difference between the spectral irradiance characteristics of the sun and of the test cell lamps also causes temperature differences. The vehicle glass absorbs more energy from the IR lamps, resulting in higher windshield temperat ures and lower IP temperatures. Although the spectral irradiance of the metal halide lamps approximates that of the sun more closely than that of the IR lamps, significant differences between vehicle temperatures were recorded in
the test cell and outdoors.

These results indicate that a vehicle thermal soak can be performed in a test cell to heat the passenger compartment in preparation for a cool down test or SCO3 emissions test. However,
a test cell should not be used to determine a vehicle’s skin temperatures or maximum component temperatures. Also, caution should be ta ken in using test cell solar lamps to assess

41advanced solar reflective glazing, because the incident angle, projected area, and spectral characteristics will not repres ent actual solar conditions



### 3.0 Application to Heavy-Duty Vehicles

Many of the thermal load reduc tion and improved comfort technol ogies investigated for lightduty vehicles can be applied to heavy-duty ve hicles as well. Light-duty vehicles, used intermittently throughout the day, average 12,000 miles per year. They are often driven after being parked in the sun for an extended period of time; therefore, the A/C system is designed to cool the passenger compartment rapidly after a heat soak. Heavy-duty vehicles are different; typically, they are used conti nuously throughout the day and average 120,000 miles per year. Thus, heavy-duty vehicle owners and operators can be sensitive to operating costs.

For example, truck drivers are often inside the vehicle’s cab during loading or unloading of the vehicle or during regulated rest periods; at those times, climate control is usually needed. When the engine is operating, the interior is cool; minimizing heat gain from the environment in summer is thus critical to reduce steady-state A/C fuel use. The main engine is typically idling to provide power to the A/C system unless an auxiliary power unit is used. A study by Argonne National Laboratory estimates that long- haul trucks idle an average of 1830 hours per year (see www.transportation.anl.gov/re search/technology_analysis/idling.html).

As our awareness of the emissions resulting from idling trucks increases, regulations are being created to ban idling in metropolitan areas. Reducing the thermal load and targeting cooling and heating to occupants can eliminate the need for idling the main engine while the vehicle is stopped. A smaller auxiliary-powered A/ C system can then provide climate control,
or comfortable conditions can be maintained without active h eating and cooling. Drivers’ comfort is also important; fleet operators want to create a comfortable environment in the cab to retain trained and experienced drivers.

The activities discussed in this section were funded by DOE through NREL’s VALR task as well as ongoing Advanced Vehicle Testing Ac tivity work under NREL’s CoolCab task. The goal of CoolCab work is to evaluate advan ced vehicle thermal management technologies for light-duty vehicles in heavy-duty vehicles application.

3.1 International Truck/Guardian I ndustries Infrared Reflective Glazing In 2001, NREL, International Tr uck, and Guardian Industries conducted a joint medium-duty truck project to examine the potential fuel economy impacts of improving the thermal management of the driver cab using infrared reflective (IRR) laminated glass. The project’s objective was to characterize the thermal pe rformance of the cabins of Class 6 Series 4300 “Next-Generation Vehicle” (NGV) trucks, test th e effect of Guardian Industries’ IRR window glazing on the cabin’s thermal environment and performance, and quantify any potential effects on the sizing and fuel economy of a truck’s A/C system.

42The cabin’s thermal performance was characte rized using a side-by-side test of two International Class 6 NGV trucks exposed to th e same hot ambient thermal environments, as defined by ambient temperature, humidity, and direct/indirect solar fl ux conditions. The test
was carried out at Atlas DSET test fac ilities in Phoenix, Arizona (Figure 45).

Figure 45. International Class 6 Series 4300 truck test outside Phoenix, Arizona
A non-dimensional thermal analysis was conducte d to establish the important cabin design and environmental parameters governing the cab in’s thermal behavior and response and to lay the foundation for interpreting test data and future testing. An additional thermal analysis of the test data wa s performed to estimate the ther mal conductance of the cabin’s ceiling, left and right doors, and rear wall. Using the temperature differential and heat flux data gathered during the testing, researchers estimated the effective cabin thermal conductance (the inverse of thermal resistance) as follows, for a Class 6 NGV truck cabin:

Left door: 4.2 W/m 2

- ° C

Right door: 3.6 W/m 2

- ° C

Ceiling: 10.0-11.0 W/m 2

- ° C

Rear wall: 1.2 W/m 2

- ° C

Vehicle experimental results showed that IRR glazing had strong impacts on many interior cabin component and air temperatur es. The difference between the breath air temperatures is highlighted in Figure 46, showing a reduction of 4.7oC when the maximum ambient temperature was attained. The IRR windshield/sidelight combination reduced maximum component and cabin air temperatures by the following values:

Cabin air temperature: 4.7 ° C Interior windshield temperature: 7.2 ° C Door interior window temperature: 2.3-5.8 ° C Instrument panel temperature: 6.6 ° C Inside door temperature: 1-1.5 ° C

430.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Test Time 0 100 200 300 400 500 600 700 800Solar Intensity [W/m2]

10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0Temperature [C] Solar Intensity & Cabin Breath-Level Temperature (11/08/01)

Solar Intensity (W/m 2 ) Breath-Level, Baseline Vehicle Breath-Level, IRR Glass Vehicle Breath-Level, Baseline Vehicle Breath-Level, IRR Glass Vehicle Ambient Temperature

International Class 6, Series 4300 Truck Cabin Tests

4.7 ° C12 Noon

Windshield & Sidelights Replaced With IRR Glazings

NREL, Golden, CO; T.J. Hendricks 12/19/01

Figure 46. Cabin breath-level air temperature with IRR windshield and sidelights

A combined A/C system/vehicle modeling analysis yielded best estimates for fuel economy improvements resulting from the lower cabin air temperatures in the International Class 6
NGV truck as follows:

SC03/CSHVR drive cycles: 0.2 to 0.3 mpg increase over a baseline of 11.3 mpg Constant 65-mph cycle: 0.0 mpg increase over a baseline of 11.8 mpg

Fuel economy increases of about 2% in the SC03 and City-Suburban Heavy Vehicle Route (CSHVR) drive cycles are believed to be a ssociated with the stop-start nature and acceleration/deceleration characteristics of the drive cycles, as well as the associated accelerations/decelerations of the A/C compressor during these drive cycles.

3.2 Schneider/Freightliner IR Imaging NREL conducted an IR imaging test with Sc hneider National and Fr eightliner. The main objective was to perform a qualitative comparison of two different truck cab insulation packages (standard vs. “super”) using infrar ed imaging. Schneider National is a large truckload carrier headquartered in Green Bay, Wisconsin. Schneider uses 15,000 drivers to operate more than 11,000 trucks and each truck averages about 120,000 miles per year. Freightliner LLC manufactures the majority of trucks operated by Schneider. Two Freightliner Century Class truck cabs were the subjects of this field test.

Freightliner, recognizing the need for improved cab insulation to meet cooling requirements during summer months, provided Sc hneider with 25 evaluation tr uck cabs equipped with an

44upgraded or super insulation package. Schneider provided two truck cabs (one standard and one super-insulated) for IR testin g to evaluate the impact of the upgraded insulation package
on heat loss.

The two test truck cabs were parked for testin g in a vacant area of Schneider’s Green Bay Operating Center parking lot. Both cab interiors were heated to similar temperatures. Initially, the truck cabs were parked apart to allow su fficient space between to capture individual images of each truck cab. As the test progre ssed, one truck cab (super-insulated) was moved closer to the other truck cab to allow images that contained both truck cabs together (Figure 47). The ambient temperature was approximate ly 0oC and the imaging was conducted at night. These were good conditions in which to evaluate the differences in insulation packages.

Figure 47. IR imaging test setup at Schneider’s Green Bay facility

Several areas, identified through differences in surface temperatures, show the potential of improving insulation to further reduce heat loss. These areas were evident in both the standard and super-insulated truck cabs and include the following:

• Driver and passenger foot wells

• Front overhead storage support

• Optional sunroof area and ceiling pad

• Rear of upper bunk

• Underneath auxiliary heater.

A difference of about 2 ° C was observed in comparing exterior surface temperatures of the baseline and super-insulated truck cabs (Figure 48 ). This difference indicates the performance improvement found in the super-insulated truck cab.

45*>9.7°

9.0

8.0

7.0

6.0

*<5.4° Base Super

Figure 48. IR image of the baseline and super-insulated truck cabs

The test results established a baseline for typical truck cab insulation while identifying the potential for reducing heating and cooling loads. The testing also identified the high-heat-loss areas within the truck cab that may have the greatest potential for improvement.

3.3 Volvo Truck Test Volvo provided a Class 8 truck cab to NREL to help investigate potential reductions in the truck cab’s thermal load as part of the CoolCab project (Figure 49). The main objective of this testing was to identify opportunities to reduce the thermal load inside the truck cab in order to reduce fuel consumption by imp roving system efficiency.

Figure 49. Volvo truck cab test setup

Testing began with establishing a baselin e for typical truck cab insulation. Simple modifications (such as adding window insulati on and applying a sleeper isolation curtain) were made to the Volvo truck cab to help understand heat loss paths. Using an NREL Freightliner Century Class truck cab for reference, tests were performed to quantify the overall heat transfer coefficient (UA) in both the Volvo and Freightliner truck cabs:

46

## ( )

ambient nteriori TTUAQ

− =

.

We measured a UA of 65 W/K for the Volvo tr uck cab. Closing the sleeper curtain reduced the UA by 15%, which indicates reduced heat tran sfer between the interi or and environment. The UA was reduced 20% by installing shades in all the windows. We measured an average air temperature rise above ambient of 10oC for the baseline Volvo case and an average air temperature rise above ambient of 5oC w ith windows covered under soak conditions. The white Freightliner truck cab had an average air temperature rise above ambient of 7oC.

Reducing the load could reduce the size, cost, and weight of idle reduction technologies. Working with industry, the CoolCab task is a pplying a systems approach to improving truck efficiency and reducing fuel use.

3.4 International Truck Test and CFD Analysis

International Truck and Engine , a manufacturer of over-the-road truck cabs, approached NREL to investigate improving cab insulati on to help reduce idling and overall fuel consumption. International want s to reduce the HVAC load during drivers’ rest periods because of battery energy storage constraints. The company lent NREL a ProStar sleeper cab to help investigate potential reductions in the truck cab thermal load as part of the CoolCab project (Figure 50). Internationa l also partially funded this test and analysis program.

Figure 50. International truck cab test setup

NREL’s Freightliner Century Class truck cab was used for comparison and baseline data. UA tests were performed to quantify the overall heat transfer coefficient in both the International and Freightliner truck cabs. Solar heat soak tests were performed to quantify interior temperatures. The data obtained in the heat soak tests were also used to validate a FLUENT
CFD model of the cab that NREL had develo ped previously for International. Once the baseline testing of both truck cabs was completed, simple modifications (such as insulating

47windows and applying a sleeper isolation curtain) could be made to the International truck cab to help understand heat loss paths.

Table 2 shows results for UA and average air te mperature above ambient for the baseline and modified configurations. The baseline white Freightliner truck cab had an average cabin interior air temperature of ~8oC above ambient.

Table 2. Results from the International Truck Cab Tests

Base or
Unmodified
Case Sleeper Curtain Closed (change from base) Arctic Curtain Closed (change from base) Windows Insulated (change from base)

UA 50 W/K -20% -25% -13% Avg. cab T air above ambient 11oC -1oC -3oC -4oC

The magnitude of the UA and temperature rise above ambient were similar to those of the
Volvo tests described in Section 3.3. The use of sleeper and window shades can significantly
reduce heat transfer between the cab and the environment.

3.5 Sage Electrochromics Sage Electrochromics, Inc. was involved in a program to evaluate means of reducing cabin temperatures in a Family of Medium Tactical Vehicles (FMTVs) operating in hot climates. One method for reducing cabin temperatures is to reduce the thermal load on the compartment. To that end, Sage Electrochro mics developed an electrochromic technology that can be integrated into the windshield of FMTVs. The project involved evaluating the impact on interior temperatures of Sage El ectrochromics glass installed on an FMTV under steady-state driving conditions with the A/C operating.

We applied our experience in evaluating the thermal load on passenger cars to determine the impact of the electrochromic gla ss on interior temperatures and heat transfer into an FMTV cab (Figures 51 and 52). Sage Electrochromics funded this work.

NREL prepared a model of an FMTV using a surface mesh and generated a final volume mesh. The next step involves collecting bound ary conditions and running the model.

48Figure 51. FMTV geometry

Figure 52. Surface mesh of the FMTV

3.6 New York City Transit Fleet In a recent test of hybrid buses in a New York City Transit fleet sponsored by DOE’s Advance Vehicle Testing Activity, research ers found that fuel economy dropped during summer months. The Orion 7 buses, which inco rporated BAE Systems hybrid technology, experienced up to a 26% reduction in fuel economy in summer (Figure 53), and the use of A/C is the most likely cause. Technologies that reduce fuel use in light-duty vehicles could also be applied to buses to reduce fuel consumption and improve fuel economy.

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Gen I Hybrids Gen II Hybrids Hybrid Gen I
Evaluation Year Number 1 Hybrid Gen I
Evaluation Year Number 2

Hybrid Gen II

Evaluation Year Number 1

Figure 53. Seasonal variation in mpg for hybrid buses shows impact of A/C



### 4.0 Implementation Barriers

A critical barrier to the incorporation of advanced climate-contro l technologies is the increased cost. If consumers were to demand better climate control along with lower fuel use,
automobile manufacturers would have a financ ial incentive to incorporate technologies like those discussed in this report. However, cons umers often do not know that such technologies exist. Besides reduced fuel use, additional benefits of advanced climate-control systems include improved comfort for drivers and pa ssengers, which could increase consumer
demand.

Another thermal load reduction benefit that has great potential to motivate consumer demand is child safety. In the United States, approximately 30 children per year die from heat-related injuries caused by entrapment in the passenger compartment. Lower cabin interior temperatures would provide trapped children with a better chance of survival. In a related issue, the deaths of approximately 10 child ren per year prompted the National Highway Traffic Safety Administration to require release latches insi de trunks (49 CFR Part 571). R Part 571).

Since the A/C system is not operating during corporate average fuel economy (CAFE) tests, there has not been a motivation regarding fuel economy to reduce fuel use for mobile A/C systems. Some have suggested a dding an A/C test to CAFE tests, but a barrier is the potential added complexity of such a test to properly account for thermal load reduction. If A/C is Since the A/C system is not operating during corporate average fuel economy (CAFE) tests, there has not been a motivation regarding fuel economy to reduce fuel use for mobile A/C systems. Some have suggested a dding an A/C test to CAFE tests, but a barrier is the potential added complexity of such a test to properly account for thermal load reduction. If A/C is

50included in fuel economy tests, we strongly r ecommend developing a procedure that will take into account all technologies than can reduce A/C fu el use. This is needed to motivate original equipment manufacturers (OEMs) to incorporate such technologies in their products.

In addition to cost, volume, weight, and serviceability are important considerations. The increased risk of recalls is a factor when automotive manufacturers are considering a new technology with no track record.

Also, thermal management crosses multiple disciplines for automotive OEMs, which sometimes makes system-level decisions difficult. The thermal environment and comfort of the cabin are impacted by the design choices a nd requirements of multiple groups (such as the body, glass, interior, HVAC, and seating). Beyo nd that for the cabin, thermal management of the engine, energy storage system, and power electronics add still more challenges.

Barriers to using waste heat for cabin cooling include relatively low and variable temperatures, weight, volume, corrosion, and engine back-pressure requirements. In particular, cabin cooling is re quired in stop-and-go traffic when engine waste heat is at a minimum. Furthermore, HEVs and PHEVs will generate even less waste heat. However, waste-heat utilization technolog y may be well suited for long-haul commercial vehicles.

It is often difficult to assess the performance of advanced technologies. Vehicle-level testing of thermal-load-reducing technologies such as so lar-reflective glass or paints in indoor test chambers has provided incorrect results. While outdoor soak-testing yields real performance data, several vehicles and longer test times are needed.

Additional barriers to incorpor ating advanced clima te-control technologies include these:

• A/C is often considered toward the end of the vehicle design process

• Some suppliers do not have tools for estimating fuel economy benefits

• International standards vary, for example, between the European Union (EU) and the United States, for such things as the choice of refrigerant and glass transmissivity requirements, among others

• Having multiple powertrains poses its own challenges (for example, for gasoline, diesel, hybrid, and plug-in hybrid vehicles).



### 5.0 Conclusions and Recommendations

NREL pursued a variety of avenues in efforts to improve vehicle efficiency and fuel economy by controlling the climate in a vehicle while keeping passengers comfortable. Because climate control loads can significantly impact the fuel economy and tailpipe emissions of conventional and hybrid electric vehicles, NREL worked closel y with industry to develop techniques to reduce auxiliary loads, such as climate control, in vehicles.

One critical benefit of reducing thermal loads is that occupants experience lower temperatures upon entering a heat-soaked vehicle and thus f eel less uncomfortable. Our research has shown

51that certain technologies can significantly re duce thermal loads and thus fuel consumption, such as solar-reflective glass and parked-car ventilation. In comparison, solar-reflective coatings and insulation had a lesser impact on interior temperatures. But they could become increasingly important as both cabin thermal loads and the waste heat from engines decrease in advanced vehicles. Cooling occupants through ventilated, cooled, or low-mass seats can also yield energy savings.

Using waste heat to generate cooling with thermoacoustics was not feasible for light-duty vehicles. But a thermoacoustic system has potential for generating electricity in vehicles with an abundance of waste heat, like today’s typical U.S. vehicles. In advanced vehicles like PHEVs and small diesels, there will be periods of time when there is little or no waste heat. In those cases, heat-generated electricity would not make sense.

In fact, we found that reducing fuel use is not by itself a sufficient motivation for automotive OEMs to incorporate advanced A/C technologies in U.S. vehicles. Although the price of fuel has risen in recent years, consumers are not de manding fuel-efficient A/C systems. To gain greater acceptance in this country, fuel-efficient A/C systems will have to be combined with a benefit such as improved thermal comfort. We have shown that several thermal load reduction technologies for vehicles provide this be nefit while reducing fuel consumption.

Another incentive for using fuel-efficient A/C sy stems in U.S. vehicles could come from new regulations addressing the need to reduce all vehicle-related air emissions. Automotive A/C is gaining more attention abroad as a result of th e EU F-gas regulation banning refrigerants with a global warming potential (GWP) > 150. The EU has been discussing how to deal with the carbon dioxide emissions caused by the fuel used to power A/C systems, and the California Air Resources Board (CARB) in our country has been doing the same. While increased attention is being paid to MA Cs, this also represents a unique opportunity to change the technology to reduce A/C fuel use and carbon dioxide emissions at the same time.

Because operating automobile A/C systems us es 0.46 million barrels per day of gasoline, reducing A/C fuel consumption also enhances our national energy security by enabling us to reduce oil imports. To significantly reduce fuel consumption in A/C systems, therefore, we recommend following the steps in this R&D pathway:

1. Reduce the thermal load by using solar-reflective glass or shades and parked-car
ventilation.
2. Incorporate low-mass, naturally ventilated seating (or active climate-control seating).
3. Incorporate the most efficien t A/C components available.
4. Increase the use of re-circulated air to the maximum extent possible, considering air quality, dehumidification, and safety issues, while avoidi ng condensation on windows.

5. Eliminate the overcooling and subsequent reheating of air that occurs now to achieve the desired temperature in vehicles with automatic temperature control systems.

Many of the load-reduction technologies we te sted, as well as climate-control seating, are already available for today’s vehicles. In additi on, interest in making A/C systems more fuelefficient is growing in the automotive indus try. And, as HEVs and PHEVs become more

52widespread, A/C loads will become increasingly important. Operating an A/C system during electric-powered driving will reduce the vehicle’s range and have negative impacts on the design and cost of the energy storage system . Reducing the cooling load allows the stored electrical energy to be used for propulsion. This load reduction also enables a vehicle to be designed that can use a smaller and less expensive energy storage system while maintaining the same range.

This work was, and is, worthy of federal support and funding for the following reasons:

• The national energy security benefit re sulting from reducing the 0.46 million barrels of gasoline used per day to power A/C systems.

• The risk of developing some advanced technologies (such as thermoacoustics and thermoelectrics) is more than the automotive industry can readily incur.

• Because vehicle cabin thermal manageme nt involves multiple disciplines and technologies, automobile manufacturers can benefit from the systems perspective provided by projects carried out at a national laboratory.

• National laboratories can provide objective, unbiased analyses.

• The tools, modeling capabilities, and experimental methods needed to develop these technologies are often beyond the capabilitie s of the suppliers who will need to produce the technologies for the automotive industry.

• Fuel-efficient A/C systems and reduced thermal loads will help advanced vehicles to operate more efficiently while re ducing greenhouse gas emissions.

53

### Appendix A. Project Partners

We would like to acknowledge all the partners that have supported our work during the past 12 years. Without their support and contributions, our research would have not have been as
successful.

Automotive industry partners were Chrysler Co rporation, Ford Motor Company, and General

Motors.

Automotive parts and equipment project partne rs and suppliers included 3M, Amerigon, BOS, BSST, Delphi, Guardian International, Johnson Controls, Measurement Technology Northwest, Modine, PPG, Sage Electrochromic s, Solutia, Southwall, Thermacore, Valeo, Visteon, W.E.T. Automotive Systems, and Webasto.

Software companies and tools that enabled us to conduct this research included ANSYS, AVL, BETA CAE Systems (ANSI), Cullimore and Ring Technologies (SINDA/FLUINT), FLUENT, ICEM CFD, and ThermoAnalytics (RadTherm).

Several government groups have also contributed to this work, including CARB, NASA, the U.S. Army, the U.S. Department of Energy, and the U.S. EPA. Other organizations that have contributed include the Society of Automotive Engineers and the University of California, Berkeley.

54

### Appendix B. Chronology and Project Summaries

Figure 54 shows an overview of NREL’s Vehicle Ancillary Load Reduction task. The top arrows indicate the major R&D tools that were developed; the horizontal bars show key industry partners for different phases of the overall project.

In addition, the following pages summarize the work of each year of the task, including the budget, key activities, technical papers, and significant presentations. To access a document, simply click on the title.

Figure 54. Vehicle Ancillary Load Reduction project timeline

55Vehicle Ancillary Load Reduction Project, FY 1996 and FY 1997

Funding

NREL: $391K

Key Accomplishments Modeling and Analysis

1. Completed ADVISOR modeling to show A/C fuel use fo r selected vehicles over various drive cycles.
2. Completed preliminary estimate of national A/C fuel use.
3. Wrote ejector cooling system model.

Testing

1. Outfitted a Plymouth Breeze with electrochromic sunroof, PV cabin ventilation, and liquid cooled/heated

seats.
2. Completed modeling and testing of automotive window boundary layer control.

Significant Presentations

1. Presented results to automotive manufacturers and suppliers and to DOE.

Other

1. Filed patent application “Vehicle Cabin Cooling System for Capturing and Exhausting Heated Boundary Layer Air from Inner Surfaces of Solar Heated Windows,” leading to U.S. Patent No. 6,186,886.
2. Exhibited technologies for reducing vehicle ancillary loads at the Third International Vehicle Thermal Management Systems Conference; May, 1997, Indianapolis, Indiana.

56Vehicle Ancillary Load Reduction Project, FY 1998

Funding

DOE: $500K

Key Accomplishments Modeling and Analysis

1. Model results showed that a 400W ancillary load changes fuel economy of a 28-mpg vehicle by 1 mpg and an 80-mpg vehicle by 6.5 mpg.
2. Model results showed significant reduction of volatile organic components in new and aged vehicles.
3. Modeled benefits of cabin ventilation on occupant thermal comfort.
4. Completed transient 16-segment thermal comfort model that predicts thermal sensation and predicted percent dissatisfied as a function of time and cabin conditions (temperature, humidity, air velocity, and solar load).

Testing

1. Grew and characterized bacteria co llected from vehicle climate control systems. Completed prototype photocatalytic oxidation air cleaner to reduce outside ai r requirements. Test results showed reductions of 90 to 100% of formaldehyde, acetaldehyde, and acetone.
2. Measured optical properties of industry solar reflective coating
3. Experimental results showed that boundary layer control with 0.5 cfm/liner foot of window removed as much heat as active cabin ventilation but with 30 to 50% less power.

Technical Papers

1. Farrington, R. B.; Brodt, D. L.; Burch, S. D.; Keyser, M. A. “Opportunities to Reduce Vehicle Climate
Control Loads.” International Electric Ve hicle Symposium and Expo sition Proceedings, EVS-15 ; October, 1998, Brussels, Belgium

.

Significant P resentations

1. Farrington, R. B.; Brodt, D. L.; Burch, S. D.; Keyser, M. A. “Opportunities to Reduce Vehicle Climate Control Loads.” Presented at the International Electric Vehicle Symposium and Exposition, EVS-15, October, 1998, Brussels, Belgium.

Other

1. Sponsored NREL/Industry Meeting titled “Partnering to Enhance Vehicle Climate Control Systems.” August, 1998.

57Vehicle Ancillary Load Reduction Project, FY 1999

Funding

DOE: $1,108K

Key Accomplishments Modeling and Analysis

1. Completed drive cycle assessment of A/C contributions to tailpipe emissions and impacts of A/C on fuel economy over the SC03 drive cycle used in the supplemental test procedure (SFTP).
2. Completed prediction of air and dash temperatures for a range of glazing optical properties and cabin
ventilation rates.
3. Completed model of reductions of heating and cooling power requirements as a function of recirculation rates and ambient conditions (temperature and humidity).

Testing

1. Developed co-heating test method to measure impacts of solar reflective glazings on solar loads.
2. Modified Dodge Neon test bed to evaluate passive cabin ventilation.
3. Measured A/C fan power consumption.
4. Documented Dodge Neon cabin soak conditions. Heat flux sensors showed that roof insulation can increase cabin soak temperatures.

5. Testing of cooled seats showed necessity for thermal comfort model. Cold surfaces cause vasoconstriction, unlike heated seats, which lead to vasodilation and muscle relaxation.

Technical Papers

1. Farrington, R. B.; Anderson, R.; Blake, D. M.; Burch, S. D.; Cuddy, M. R.; Keyser, M. A.; Rugh, J. P. “Challenges and Potential Solutions for Reducing Climate Control Loads in Conventional and Hybrid
Electric Vehicles.” Fourth International Vehicle Thermal M anagement Systems Conference Proceedings; May, 1999, London, United Kingdom

. 2. Farrington, R.; Cuddy, M.; Keyser, M.; Rugh, J. "Opportunities to Reduce Air-Conditioning Loads Through Lower Cabin Soak Temperatures." International Electric Vehicle Sym posium and Exposition Proceedings,
EVS-16 ; October, 1999, Beijing, China . NREL Report No. CP-540-25975.

Significant Presentations

1. Farrington, R. B.; Anderson, R.; Blake, D. M.; Burch, S. D.; Cuddy, M. R.; Keyser, M. A.; Rugh, J. P. “Challenges and Potential Solutions for Reducing Climate Control Loads in Conventional and Hybrid Electric Vehicles.” Presented at the Fourth International Vehicle Thermal Management Systems Conference Proceedings; May, 1999, London, United Kingdom.
2. Farrington, R.; Cuddy, M.; Keyser, M.; Rugh, J. "Opportunities to Reduce Air-Conditioning Loads Through Lower Cabin Soak Temperatures." Presented at the International Electric Vehicle Symposium and Exposition, EVS-16. October 17, 1999, Beijing, China.

Other

1. Technical Monitor of DOE Cooperative Automotive Research for Advanced Technology Program (CARAT).

a. New Higher Performance Low Cost Selective Solar Radiation Control Coatings Energy Conversion Devices
b. Development of Vehicle Magnetic Air Conditioner (VMAC) Technology Iowa State University/Astronautics Corporation of America

c. High-Efficiency Motor for Vehicle Power Accessories Visual Computing Systems, Kentucky
d. Climate Control Seating Life Enhancement Technologies
2. Participated in Third International Meeting on Thermal Manikin Testing, October 1999, Stockholm, Sweden.

58Vehicle Ancillary Load Reduction Project, FY 2000

Funding

DOE: $1,108K

Key Accomplishments Modeling and Analysis

1. Demonstrated the first stage of the vehicle integrat ed modeling process on the Chrysler ESX3 hybrid vehicle. Completed a steady state thermal model using FLUENT and the ICEM CFD cabin modeler.
2. Hosted Automotive Glazing R&D Panel (May, 2000) with participation by 3M, Chrysler, DOE, Ford, PPG, SAE, Southwall, and Visteon Glass.
3. Developed a SINDA/FLUINT air-conditioning model with an integrated lump-capacitance cabin model to predict cabin cooldown including evaluation of heat-pipe instrument panel thermal rejection system.

Testing

1. Assessed the impact of a 3M non-metallic solar reflective film in a Chrysler minivan thermal soak test in
Golden and Phoenix.
2. Completed a vehicle thermal soak test using black Ford Explorers in Golden and Phoenix (3M prototype non-metalic solar reflective film).
3. Completed conceptual design of a thermal manikin an d experimentally evaluated various skin heating and sweating concepts.

Technical Papers

1. Rugh, J.P.; Howard, R.S.; Farrington, R.B.; Cuddy, M.R.; Blake, D.M. "Innovative Techniques for Decreasing Advanced Vehicle Auxiliary Loads." Future Car Congress 2000 Proceedings; April, 2000, Arlington, Virginia . SAE Document No. 2000-01-1562. NREL Report No. JA-540-27225.
2. Farrington, R.B.; Rugh, J.P.; Barber, G.D. "Effect of Solar-Reflective Glazing on Fuel Economy, Tailpipe Emissions, and Thermal Comfort." 2000 International Body Engineering Conference Proceedings; October 3-5, 1999, Detroit, Michigan . SAE Document No. 2000-01-2694. NREL Report No. 28779.
3. Farrington, R.; Rugh, J. "Impact of Vehicle Air-Conditioning on Fuel Economy, Tailpipe Emissions, and Electric Vehicle Range." Earth Technologies Forum Proceedings; October 31, 2000, Washington, D.C. NREL Report No. CP-540-28960.
4. Huang, Z.; Maness, P. C.; Blake, D. M.; Wolfrum, E. J.; Smolinski, S. L.; Jacoby, W. A. (2000). Bactericidal Mode of Titanium Dioxide Photocatalysis. Journal of Photochemistry and Photobiology A: Chemistry . Vol. 130, January 2000; pp. 163-170; NREL Report No. JA-590-27085.

5. Huang, J.; Farrington, R.; Maness, P. C.; Huang, Z.; Blake, D.; Wolfrum, E.; Manvi, R.; Kern, R. (2000). Effect of Titanium Dioxide Photocatalytic Oxidation on Fungal Spore Germination. Abstract Q-110. Abstracts of the American Society for Microbiology 100th General Meeting , 21-25 May 2000, Los Angeles,California. Washington, DC: American Society for Microbiology (ASM) p. 565; NREL Report No. AB510-35823.

Significant Presentations

1. Rugh, J.; Howard, R.; Farrington, R.; Cuddy, M.; Blake, D. "Innovative Techniques for Decreasing Advanced Vehicle Auxiliary Loads." Presented at the Future Car Congress 2000. April, 2000, Arlington, Virginia. SAE Paper No. 2000-01-1562.
2. Farrington, R.; Rugh, J.; Barber, G. "Effect of Solar-Reflective Glazing on Fuel Economy, Tailpipe Emissions, and Thermal Comfort." Presented at the International Body Engineering Conference. October, 2000. SAE Paper No. 2000-01-2694.
3. Farrington, R. "Vehicle Testing to Determine the Benefits of 3M Solar Reflective Film." Presented to Chrysler. February 29, 2000.
4. Rugh, J. "Vehicle Testing to Determine the Benefits of 3M Solar Reflective Film." Presented to Ford. October 25, 2000.

595. Rugh, J. "Integrated Vehicle Systems Analysis - ESX3 Final Analysis - Glazing Update." Presented to the Department of Energy. August 30, 2000.
6. Farrington, R.; Rugh, J. "Impact of Vehicle Air-Conditioning on Fuel Economy, Tailpipe Emissions, and Electric Vehicle Range." Presented at the Earth Techno logies Forum. October 31, 2000, Washington, D.C.

60Vehicle Ancillary Load Reduction Project, FY 2001

Funding

DOE: $1,586K

Key Accomplishments Modeling and Analysis

1. Assessed heat-generated cooling opportunities, includ ing absorption, metal hydride absorption, desiccant, and thermoacoustic systems.
2. Wrote optimization software for heat-generated electricity with thermoelectric devices.
3. Developed a solar radiation model that calculates the solar spectral irradiance incident on the vehicle for 239
locations in the U.S.
4. Developed an interactive vehicle solar load estimator (VSOLE) to predict the transmitted, absorbed, and reflected energy of vehicle glazings for various ligh t sources, vehicle types, vehicle orientation, and locations, including parametric analysis.

5. Developed a detailed transient, two-phase A/C model in SINDA/FLUiNT analysis software with optimization capability.

Testing

1. Completed vehicle testing of two Lincoln Navigators in a collaborative effort with Ford and Tier 1 suppliers to measure the impact of advanced technologies on reducing vehicle soak temperature including solar infrared reflective glazings, visibly reflective glazings, reflective shades, gas-filled body insulation, reflective roof surfaces, and active and passive parked car ventilation.
2. Completed vehicle testing of Jeep Grand Cherokee in a collaborative effort with Chrysler to validate integrated modeling techniques.
3. Developed and tested passively cooled instrument panel using heat pipes demonstrating significantly lower peak IP and air temperatures.
4. Evaluated PPG solar reflective glazing with two white Ford Explorers in Phoenix.

5. Built a prototype thermal manikin leg with sweating, heated segments.

Technical Papers

1. Farrington, R.; Barber, G.; Hendricks, T.; Marion, W.; Markel, T.; McGuffin, R.; Rugh, J. "Integrated Modeling to Predict Occupant Thermal Comfort." 7th International Automotive Technologies Association Conference Proceedings; May, 2001 , Florence, Italy. NREL Report No. 29898.
2. Hendricks, T.J. "Milestone Report - Vehicle Transient Air Conditioning Analysis: Model Development & System Optimization Investigations." June, 2001 . NREL Report No. TP-540-30715.
3. Cullimore, B.A.; Hendricks, T.J. "Design and Transient Simulation of Vehicle Air Conditioning Systems."
Fifth Vehicle Thermal Management Systems Conference &Exhibition Proceedings ; May, 2001, Nashville, Tennessee

. 4. Rugh, J.; Hendricks, T.; Koram, K. "Effect of Solar Reflective Glazing on Ford Explorer Climate Control, Fuel Economy, and Emissions." International Body Engineering Conference & Exposition Proceedings; October, 2001

. 5. Rugh, J.; Farrington, R.; Boettcher, J. "The Impact of Metal-Free Solar Reflective Film on Vehicle Climate
Control." Fifth Vehicle Thermal Management Syst ems Conference &Exhibition Proceedings ; May, 2001, Nashville, Tennessee

. 6. McGuffin, R. "Modeling of Human Thermal Comfort." SAE 5th Vehicle Thermal Management Conference Proceedings; July, 2001

. 7. Burke, R.; McGuffin, R. "Development of an Advanced Thermal Manikin for Vehicle Climate
Evaluation." 4IMM Conference Proceedings; September, 2001.
8. Hendricks, T.J. "Optimization of Vehicle Air Conditioning Systems Using Transient Air Conditioning Performance Analysis." Fifth Vehicle Thermal Management System s Conference & Exhibition Proceedings; May, 2001, Nashville, Tennessee. Paper No. 2001-01-1734.

619. Hendricks, T.J.; Thoensen, T. "Experimental Demonstration of Heat Pipe/Two-Phase Flow Systems for Vehicle Passenger Cabin Cooling." 2001 ASME International Mechanical Engineering Congress and Exposition (IMECE2001) Proceedings ; November 11-16, 2001, New York, New York. Heat Transfer Division Vol. 369-7. NREL Paper No. 30741.

Significant P resentations

1. Farrington, R.; Barber, G.; Hendricks, T.; Marion, W.; Markel, T.; McGuffin, R.; Rugh, J. "Integrated Modeling to Predict Occupant Thermal Comfort." Presented at the Seventh International Automotive Technologies Association Conference. May, 2001, Florence, Italy.
2. Hendricks, T. "Vehicle Air Conditioning Systems: Transient Analysis, Optimization & MATLAB Integration." Presented at the International SINDA/FLUINT User’s Conference. February 9, 2001, Keystone, Colorado.
3. Rugh, J.; Farrington, R.; Boettcher, J. "The Impact of Metal-Free Solar Reflective Film on Vehicle Climate Control." Presented at the Fifth International Vehicle Thermal Management Systems Conference, May, 2001, Nashville, Tennessee.
4. McGuffin, R. "Modeling of Human Thermal Comfort." Presented at the SAE Vehicle Thermal Management Conference. July, 2001.

5. Hendricks, T. J. "Optimization of Vehicle Air Conditioning Systems Using Transient Air Conditioning Performance Analysis." Presented at the Fifth Vehicle Thermal Management Systems Conference & Exhibition. May, 2001.
6. Rugh, J. "Analysis of Advanced Solar Reflective Glazings using the Vehicle Solar Load Estimator (VSOLE)." Presented to the Department of Energy. August 31, 2001.R ugh, J. "Vehicle Testing to Determine the Benefits of PPG Sungate ® Glazing." Presented to PPG. February 13, 2001.

7. Rugh, J. "Reduction in A/C Fuel Use Milestone Presentation." Presented to the Department of Energy. September 29, 2001.
8. Rugh, J. "Integrated Vehicle Modeling Milestone Presentation." Presented to the Department of Energy. September 29, 2001.
9. Hendricks, T. J.; Thoensen, T. "Experimental Demonstration of Heat Pipe/Two-Phase Flow Systems for Vehicle Passenger Cabin Cooling." Presented at the ASME International Mechanical Engineering Congress and Exposition (IMECE2001). November 11-16, 2001, New York, New York. Heat Transfer Division Vol.
369-7.

Other

1. Marion, W. "Solar Radiation Model for Vehicle Simulation Tools." Presented to the Department of Energy. May 29, 2001.
2. McGuffin, R. "Examination of Technologies to Reduce Cabin Solar Loads and Peak Soak Temperatures in Lincoln Navigators." Presented to Ford Motor Company.
3. Farrington, R. et al., Patent No. 6,186,886, awarded February 13, 2001.
4. Hendricks, T. J. et al., U.S. Patent No. 6,964,294 B2, filed May, 5, 2001.

5. Hendricks, T.; Johnson, V.; Keyser, M. "Heat-Gener ated Cooling Opportunities." White Paper to DOE.

62Vehicle Ancillary Load Reduction Project, FY 2002

Funding

DOE: $1,182K

Key Accomplishments Modeling and Analysis

1. Integrated the transient A/C model with the ADVISOR vehicle systems analysis software.
2. Optimized an electric-driven air conditioning system for a light-duty vehicle using the transient A/C model.
3. Analyzed and designed a metal hydride heat pump for a fuel cell vehicle.
4. Developed an A/C fuel use analysis methodology. Calculated first thermal-comfort-based A/C fuel use analysis of U.S. as a function of local ambient conditions using monthly data for 116 metropolitan areas.

Testing

1. Performed vehicle soak tests of ventilation techniques to reduce the peak soak temperature using a Jeep Grand Cherokee provided by Chrysler.
2. Tested Guardian solar reflective glazings in a Class 6 International truck in Phoenix.
3. Completed human subject tests at UC Berkeley to assess human thermal sensation and comfort in transient asymmetric thermal environments

Technical Papers

1. Hendricks, T.J.; Lustbader, J.A. (2002) "Advanced Thermoelectric Power System Investigations for Lightduty and Heavy-duty Applications: Part I." and "Advanced Thermoelectric Power System Investigations for Light-duty and Heavy-duty Applications: Part II." ICT '02: XXI International Conference on Thermoelectrics Proceedings; August 25-29, 2002, Long Beach, California. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEE) pp. 381- 394; NREL Report No. CP-540-32756 and
CP-540-35510.
2. Johnson, V. "Fuel Used for Vehicle Air Conditioning: A State-by-State Thermal Comfort-Based Approach." Future Car Congress 2002 Proceedings; June, 2002, Arlington, Virginia . SAE Paper No. 2002-01-1957.
3. Farrington, R.; Johnson, V. "The Impact of Vehicle Air-Conditioning Fuel Use and What Can Be Done to
Reduce It." Fourth Annual Earth Technology Forum Proceedings ; March 25-27, 2002, Washington

, D.C

. 4. Johnson, V. "Heat-Generated Cooling Opportunities in Vehicles." Future Car Congress 2002 Proceedings; June, 2002, Arlington, Virginia. SAE Paper No. 2002-01-1969.

5. Hovland, V. "Integrated Cabin and Fuel Cell System Thermal Management with a Metal Hydride Heat Pump." International Symposium on Metal Hydrogen Systems: Fundamentals and Applications Proceedings; September 2-6, 2002, Annecy, France.
6. Rugh, J.P. "Integrated Numerical Modeling Process for Evaluating Automobile Climate Control Systems." Future Car Congress 2002 Proceedings; June, 2002, Arlington, Virginia . SAE Paper No. 2002-01-1956.

7. McGuffin, R; Burke, R.; Huizenga, C.; Zhang, H.; Vlahinos, A.; Fu, G. "Human Thermal Comfort Model
and Manikin." Future Car Congress 2002 Proceedings; June, 2002, Arlington, Virginia . SAE Paper No.
2002-01-1955.
8. Hendricks, T. "Heat Pipe/Two-Phase Flow Systems For Vehicle Passenger Cabin Cooling." Future Car Congress 2002 Proceedings; June, 2002, Arlington, Virginia . SAE Paper No. 2002-01-1970.
9. Farrington, R. "Advanced Automotive Glazings: A Cool Idea for Hot Cars." The Society of Vacuum
Coaters 45th Technical C onference Proceedings; April 13-18, 2002, Lake Buena Vista, Florida.

63Significant Presentations

1. Hendricks, T.J.; Lustbader, J.A. "Advanced Thermoelectric Power System Investigations for Light-duty and Heavy-duty Applications." Presented at the ICT ' 02: XXI International Conference on Thermoelectrics. August 25-29, 2002, Long Beach, California.
2. Johnson, V. "Fuel Used for Vehicle Air Conditioning: A State-by-State Thermal Comfort-Based Approach." Presented at the Future Car Congress 2002. June, 2002, Arlington, Virginia. SAE Paper No. 2002-01-1957.
3. Farrington, R.; Johnson, V. "The Impact of Vehicle Air-Conditioning Fuel Use And What Can Be Done to Reduce It." Presented at the Fourth Annual Earth Technology Forum. March 25-27, 2002, Washington, D.C.
4. Johnson, V. "Heat-Generated Cooling Opportunities in Vehicles." Presented at the Future Car Congress 2002. June 5, 2002, Arlington, Virginia. SAE Paper No. 2002-01-1969.

5. Hovland, V. "Integrated Cabin and Fuel Cell System Thermal Management with a Metal Hydride Heat Pump." Presented at the International Symposium on Metal Hydrogen Systems: Fundamentals and Applications. September 2-6, 2002, Annecy, France.
6. Rugh, J.P. "Integrated Numerical Modeling Process for Evaluating Automobile Climate Control Systems." Presented at the Future Car Congress 2002. June, 2002, Arlington, Virginia. SAE Paper No. 2002-01-1956.

7. McGuffin, R. Burke, R.; Huizenga, C.; Zhang, H.; Vlahinos, A.; Fu, G. "Thermal Comfort Modeling and Manikin." Presented at the Future Car Congress 2002. June, 2002, Arlington, Virginia. SAE Paper No.
2002-01-1955.
8. Rugh, J. "Jeep Grand Cherokee Project: Test Program and Thermal/Fluid Modeling." Presented at a meeting with Chrysler. November 30, 2001.
9. Farrington, R. "Advanced Automotive Glazings: A Cool Idea for Hot Cars." Presented at the Society of Vacuum Coaters 45th Technical Conference. April 13-18, 2002, Lake Buena Vista, Florida.
10. Hendricks, T. "Class 6 Truck Cabin Ther mal Characterization." March 6, 2002.
11. Hovland, V. "An Application: A Metal Hydride Heat Pump for a Fuel Cell Vehicle." Presented to the Department of Energy. September 5, 2002.
12. Hendricks, T. “Heat Pipe/Two-Phase Flow Systems for Vehicle System Cooling.” Presented at the Future Car Congress 2002. June 5, 2002, Arlington, Virginia. SAE Paper No. 2002-01-1970.

Other

1. Hendricks, T. "Class 6 Next Generation Vehicle Cabin Thermal Characterization Investigations." Joint Project by National Renewable Energy Laboratory / International Truck & Engine Corporation / Guardian Industries Automotive Products. May, 2002.

64Vehicle Ancillary Load Reduction Project, FY 2003

Funding

DOE: $500K

Key Accomplishments Modeling and Analysis

1. Improved A/C fuel use analysis for the U.S. Applied methodology on the EU and Japan.
2. Applied an integrated modeling process to a collaborative project with Johnson Controls to assess the impact of a new distributed HVAC concept based on human thermal comfort.
3. Developed a the Human Thermal Physiological Model (a three-dimensional, finite-element model of the human thermal physiological and thermoregulatory systems to control the thermal manikin).

Testing

1. Completed fabrication and developmental testing of ADAM (the ADvanced Automotive Manikin). Compared outdoor thermal soak of a Jeep Grand Cherokee with indoor testing at Chrysler's environmental test cell (IR lamps) and the emissions cell (metal halide lamps) showed significant errors with indoor testing including much higher surface temperatures due to lamp spectrum, lack of breezes, and significantly
different radiation view factors betw een the heat source and the vehicle.

Technical Papers

1. Rugh, J.P. "Application of an Integrated Modeling Process to Evaluate an Automotive Climate Control System." Vehicle Thermal Management Systems 6 Proceed ings; May 18-21, 2003, Brighton, United Kingdom. London, UK: Institution of Mechanical Engineers pp. 303-312. NREL Report No. CP-540-33370.
2. Hendricks, T.J. "Optimization of Vehicle Air Conditioning Systems Using Transient Air Conditioning Performance Analysis." Vehicle Thermal Management Systems 6 Pr oceedings; May 18-21, 2003, Brighton, United Kingdom. NREL Report No. 29930.
3. Rugh, J.; Farrington R.; Bharathan, D.; Vlahinos, A.; Burke, R.; Huizenga, C.; Zhang, H. "Predicting
Human Thermal Comfort in a Transient Non-Uniform Thermal Environment." European Journal of Applied Physiology ; Vol. 92; 2004, Number 6; pp. 721-727.
4. Burke, R.; Rugh, J.; Farrington R. "ADAM – the Advanced Automotive Manikin." Fifth International Meeting on Thermal Manikins and Mode ling Proceedings; Strasbourg, France

. 5. Zhang, H.; Huizenga, C.; Arens E.; Wang, D. "Thermal Sensation and Comfort in Transient Non-Uniform
Thermal Environments." European Journal of Applied Physiology ; Vol. 92; 2004, Number 6; pp. 728-733.
6. Hendricks, T.; Lustbader, J. "Thermoelectric Ener gy Recovery Systems in Future Advanced Vehicle Systems." The 6th ASME-JSME Thermal Engin eering Joint Conference Proceedings ; March 16-20, 2003, Hawaii

. 7. Farrington, R.; Rugh, J. "Stay Cool with Advanced Automotive Glazings." Glass Processing Days Proceedings; June 15-28, 2003, Tampere, Finland

.

Significant Presentations

1. Farrington, R.; Coroller, P.; Malvicino, C.; Gense, R.; Clodic, D.; Hrnjak, P.; Kruse, P.; Mager, R.; Harte, S.; Hovland, V. "Fuel Consumption and Associated CO 2 Emissions due to MACs." Presented at the Mac Summit 2003. February 10, 2003, Brussels, Belgium.
2. Rugh, J; Hovland, V. "National and World Fuel Savings and CO 2 Emission Reductions by Increasing Vehicle Air Conditioning COP." Presented at the 2003 Automotive Alternate Refrigerant Systems Symposium. July 17, 2003.
3. Rugh, J. "Parked Car Ventilation WJ Test Program." Presented at meeting with Chrysler. December 12,
2002.
4. Farrington, R.; Rugh, J. "Stay Cool with Advanced Automotive Glazings." Presented at Glass Processing Days. June 15-28, 2003, Tampere, Finland.

655. Rugh, J.P. "Application of an Integrated Modeling Process to Evaluate an Automotive Climate Control System." Presented at Vehicle Thermal Management Systems 6. May 18-21, 2003, Brighton, United Kingdom. London, UK: Institution of Mechanical Engineers pp. 303-312. NREL Report No. CP-540-33370.
6. Hendricks, T.J. "Optimization of Vehicle Air Conditioning Systems Using Transient Air Conditioning Performance Analysis." Presented at Vehicle Thermal Management Systems 6. May 18-21, 2003, Brighton, United Kingdom. NREL Report No. 29930.

7. Rugh, J.; Farrington R.; Bharathan, D.; Vlahinos, A.; Burke, R.; Huizenga, C.; Zhang, H. "Predicting
Human Thermal Comfort in a Transient Non-Uniform Thermal Environment." European Journal of Applied Physiology ; Vol. 92, Number 6; pp. 721-727.
8. Burke, R.; Rugh, J.; Farrington R. "ADAM – the Advanced Automotive Manikin." Presented at the Fifth International Meeting on Thermal Manikins and Modeling. Strasbourg, France.
9. Zhang, H.; Huizenga, C.; Arens, E.; Wang, D. "Thermal Sensation and Comfort in Transient Non-Uniform
Thermal Environments." European Journal of Applied Physiology ; Vol. 92, Number 6; pp. 728-733.
10. Hendricks, T.; Lustbader, J. "Thermoelectric Ener gy Recovery Systems in Future Advanced Vehicle Systems." Presented at the 6th ASME-JSME Thermal Engineering Joint Conference. March 16-20, 2003,
Hawaii.
11. Farrington, R. "Fuel Savings from Efficient Mobile Air Conditioners." Presented at the 2003 Earth Technologies Forum. April 22-24, 2003, Washington, D.C.
12. Farrington, R.; Rugh, J. "Reducing Fuel Used for Mobil Air-Conditioners Through Solar Reflective Glazing." Presented at the ITB Group Above-The-Bent Line Modules and Systems. November, 6, 2003, Dearborn, Michigan.

66Vehicle Ancillary Load Reduction Project, FY 2004

Funding

DOE: $964K WFO: US EPA $70K

Key Accomplishments Modeling and Analysis

1. Modeled standing wave thermoacoustic devices capable of using waste heat to generate cooling.
2. At the request of SAE, compared GM and EU Life Cycle Climate Performance analyses of mobile air conditioning systems.
3. Completed the Human Thermal Physiological Model.
4. Completed the Human Thermal Comfort Empirical Model.

Testing

1. Completed fabrication of the thermal manikin (ADAM) and used the improved human thermal physiological model to simulate skin temperatures within approximately +3/-1oC of published results.
2. Thermal soak tested a prototype Chrysler HEV with advanced thermal management technologies.
3. Designed and demonstrated a standing wave thermoacoustic device capable of using waste heat to generate cooling.
4. Measured a 2.8 to 4.5% reduction in automotive air-conditioning fuel use by improving thermal comfort with a ventilated seat prototype.

Technical Papers

1. Farrington, R; Rugh, J.; Bharathan, D. "Use of a Thermal Manikin to Evaluate Human Thermoregulatory Responses in Transient, Non-Uniform, Thermal Environments." International Conference on Environmental Systems Proceedings; July 19-22, 2004, Colorado Springs, Colorado . SAE Paper No. 2004-01-2345.
2. Rugh, J.; Malaney, V. "Comparison of Indoor Vehicle Thermal Soak Tests to Outdoor Tests." 2004 SAE Congress Proceedings; Detroit, Michigan . SAE Paper No. 2004-01-1376.
3. Rugh, J.; Hovland, V. Andersen, S. "Significant Fuel Savings and Emission Reductions by Improving Vehicle Air Conditioning." Mobile Air Conditioni ng Summit Proceedings ; April 14-15, 2004

, Washington,
D.C

.

Significant Presentations

1. Farrington, R; Rugh, J.; Bharathan, D. (2004) "Use of a Thermal Manikin to Evaluate Human Thermoregulatory Responses in Transient, Non-Uniform, Thermal Environments." Presented at the 2004 International Conference on Environmental Systems. July 19-22, 2004, Colorado Springs, Colorado. SAE Paper No. 2004-01-2345.
2. Rugh, J.; Malaney, V. "Comparison of Indoor Vehicle Thermal Soak Tests to Outdoor Tests." Presented at the 2004 SAE Congress. Detroit, Michigan. SAE Paper No. 2004-01-1376.
3. Rugh, J.; Hovland, V.; Andersen, S. "Significant Fuel Savings and Emission Reductions by Improving Vehicle Air Conditioning." Presented at the Mobile Air Conditioning Summit, April 14-15, 2004, Washington, D.C.
4. Rugh, J. "Comparison of Two Mobile A/C LCCP Analyses." Presented at the 2004 Alternate Refrigerant Systems Symposium. June 28-July 1, 2004, Scottsdale, Arizona.

5. Rugh, J.; Gooding, S. "Vehicle Soak Testing of Lightweight Vehicle with Advanced Thermal Management Technologies." Presented to Chrysler. November 17, 2004.
6. Keyser, M.; King, C. "FY04 Milestone 6.2 Report Light Vehicle Ancillary Systems Heat Generated Cooling Using A Standing Wave Thermoacoustic Engine/Heat Pump." Presented to the Department of Energy. September 30, 2004.

67Other

1. Established CRADA with AVL to investigate integrated modeling concepts based on thermal comfort.
2. Built the Waste Heat Utilization Laboratory.

3. Completed Vehicle Climate Control Laboratory (VCCL) including an automobile passenger compartment (Dodge Neon), heated with solar lamps, temperature measurement, and automotive A/C cooldown

.

68Vehicle Ancillary Load Reduction Project, FY 2005

Funding

DOE: $1141K WFO: US EPA $250K

Key Accomplishment Modeling and Analysis

1. Applied NREL's A/C fuel use analysis methodology to the country of India under EPA funding.
2. Started applying the integrated modeling process to a Cadillac STS.
3. Improved the Human Thermal Comfort Empirical Model.

Testing

1. Completed validation/calibration testing of ADAM with jury test results in the literature. Assessed thermalload reduction in a thermal soak test using two Cadillac STSs as part of the industry/government/SAE IMAC Cooperative Research Program.
2. Evaluated two types of advanced seating technology with W.E.T. and Amerigon. Determined the potential
to reduce A/C fuel use.
3. Completed testing of the standing wave thermoacoustic engine/heat pump and designed a modular standing/traveling wave thermoacoustic engine.

Technical Papers

1. Rugh, J.; Bharathan, D. "Predicting Human Thermal Comfort in Automobiles." Seventh Vehicle Thermal Management Systems Conference Proceedi ngs; May 10-12, 2005, Toronto, Canada . SAE Paper No. 2005-
01-2008.
2. Wolfahrt, J.; Baier, W.; Wiesler, B.; Raulot, A.; Rugh, J.; Bharathan, D.; Kußmann, C. "Aspects of Cabin Fluid Dynamics, Heat Transfer, and Thermal Comfort in Vehicle Thermal Management Simulations." Seventh Vehicle Thermal Management Systems Conf erence Proceedings; May 10-12, 2005, Toronto,
Canada. SAE Paper No. 2005-01-2000.
3. Lustbader, J. "Evaluation of Advanced Automotive Seats to Improve Thermal Comfort and Fuel Economy." Seventh Vehicle Thermal Management Systems Conf erence Proceedings; May 10-12, 2005, Toronto,
Canada . SAE Paper No. 2005-01-2056.
4. Farrington, R.; Rugh, J.; Bharathan, D.; Paul, H.; Bue, G.; Trevino, L. "Using a Sweating Manikin, Controlled by a Human Physiological Model, to Evaluate Liquid Cooling Garments." 35th International Conference on Environmental Systems Proceed ings; July 11-14, 2005, Rome, Italy . SAE Paper No. 2005-
01-2971.

Significant Presentations

1. Rugh, J.; Bharathan, D. "Predicting Human Thermal Comfort in Automobiles." Presented at the 7th Vehicle Thermal Management Systems Conference. May 10-12, 2005, Toronto, Canada. SAE Paper No. 2005-01-
2008.
2. Lustbader, J. "Evaluation of Advanced Automotive Seats to Improve Thermal Comfort and Fuel Economy." Presented at the 7th Vehicle Thermal Management Systems Conference. May 10-12, 2005, Toronto, Canada. SAE Paper No. 2005-01-2056.
3. Farrington, R.; Rugh, J.; Bharathan, D.; Paul, H.; Bue, G.; Trevino, L. "Using a Sweating Manikin, Controlled by a Human Physiological Model, to Evaluate Liquid Cooling Garments." Presented at the 35th International Conference on Environmental Systems. July 11-14, 2005, Rome, Italy. SAE Paper No. 2005-
01-2971.
4. John Rugh, J.; Bharathan, D; Chaney, L. "Predicting Human Thermal Comfort in Automobiles." Presented at the AVL Advanced Simulation Technologies User Meeting 2005. June 13, 2005, Graz, Austria.

5. Rugh, J. "How Diverse Powertrains Affect Thermal Management." Presented during a Research Forum Panel, 7th Vehicle Thermal Management Systems Conference. May 11, 2005, Toronto, Canada.

696. Rugh, J. "SAE Improved Mobile Air Conditioning Cooperative Research Program." Presented at the 2005 Mobile Air Conditioning Summit. March 15-16, 2005, Sacramento, California.

7. Rugh, J. "Measuring Indirect Emissions of MACs." Pr esented at Session 3 – Research Activities and Panel Discussion at the 2005 Mobile Air Conditioning Summit. March 15-16, 2005, Sacramento, California.
8. Keyser, M.; King, C. "Ancillary Loads Milestone 6.3.2 Investigate and Research New Heat Exchangers and Regenerators for a Traveling Wave Thermoacoustic System." Delivered to the Department of Energy. August 31, 2005.

Other

1. Invited participation at SAE’s VTMS7 Conference res earch forum panel entitled "How Diverse Powertrains Affect Thermal Management."

70Vehicle Ancillary Load Reduction Project, FY 2006

Funding

DOE: $892K WFO: NASA $76K US EPA $50K

US Army (USAARL) $10K Sage
Electrochromics $20K

SAE $54K BSST $30K

Key Accomplishments Modeling and Analysis

1. Used AVL software in the Cadillac STS thermal analysis (Improved Mobile Air Conditioning Cooperative Research Program) to model the thermal/fluid environment in the passenger compartment during soak and
cooldown.
2. Determined the A/C fuel use impact of Cadillac STS thermal load reduction technologies tested in the
summer of 2005.
3. Performed an A/C fuel use analysis of Mexico City with EPA funding.

Testing

1. Tested the best load reduction technologies in a thermal soak test using Cadillac STSs (Sungate EP, solarpowered parked car ventilation, solar reflective paint).
2. Completed NASA Liquid Cooling Garment testing using ADAM and the Manikin Environmental Chamber.
3. Completed thermoacoustic traveling wave prototype component testing.
4. Assessed an Amerigon Thermoelectric cooled seat using ADAM to determine improvement in thermal comfort and potential to reduce A/C fuel use.

Technical Papers

1. Rugh, J.; King, C.; Paul, H.; Bue, G.; Trevino, L. "Phase II Testing of Liquid Cooling Garments Using a Sweating Manikin, Controlled by a Human Physiological Model." 36 th International Conference on Environmental Systems Proceedings; Ju ly 17-20, 2006, Norfolk, Virginia . SAE Paper No. 2006-01-2239.

Significant Presentations

1. Rugh, J.; King, C.; Paul, H.; Bue, G.; and Trevino, L. "Phase II Testing of Liquid Cooling Garments Using a Sweating Manikin, Controlled by a Human Physiological Model." Presented at the 6th International Conference on Environmental Systems. July 17-20, 2006, Norfolk, Virginia. Paper No. 2006-01-2239.
2. Rugh, J.; Gooding, S. "I-MAC Vehicle Testing of Advanced Thermal Management Technologies." Presented to the I-MAC Core Team. October 27, 2005, Troy, Michigan.
3. Rugh, J. "Impact of Cadillac STS Ventilated Seat on Fuel Use and Thermal Comfort." Presented to the IMAC Core Team. March 7, 2006, Troy, Michigan.
4. Chaney, L. "Analysis of the Impact of Reduced Vehicle Thermal Load on AC Fuel Use." Presented at the 2006 Alternate Refrigerant Systems Symposium. June 27-29, 2006, Scottsdale, Arizona.

5. Meyer, J.; Chaney, L.; Rugh, J. "SAE Improved Mobile Air Conditioning Cooperative Research Program - Reduced Thermal Load." Presented at the I-MAC Sponsors Meeting. June 26, 2006, Scottsdale, Arizona.
6. Rugh, J.; Chaney, L.; Lustbader J. "Vehicle Thermal Management Integrated Modeling of the 2005 I-MAC Test Vehicle." Presented at the 1st European Mobile Air Conditioning Workshop. November 29-30, 2005, Orbassano, Italy.

7. Rugh, J. "Indirect Emissions from MACs." Presented to the California Air Resources Board. December 20, 2005, Sacramento, California.
8. Lustbader, J. "W.E.T. Automotive Systems MTNW & NREL Meeting." Presented at a meeting at NREL. November 17, 2005.
9. Keyser, M.; King, C. "Ancillary Loads Milestone 8.1 - Heat Generated Cooling Investigation and Research Into Thermoacoustic Systems." Presented to the Department of Energy. September 30, 2006.

7110. Thundiyl, K.; Chaney, L. "Mexico City Fuel Savings and Emission Reductions by Improving Vehicle Air Conditioning." Presented at the First Internationa l Conference on Carbon Management at Urban and Regional Levels: Connecting Development Decisions to Global Issues. September 7, 2006. NREL Report
No. PR-540-40550.

Other

1. 2006 Environmental Protection Agency (EPA) Climate Protection Award (NREL is the first DOE laboratory to earn this honor).
2. Completed Manikin Environmental Chamber (temperature and humidity control).

72Vehicle Ancillary Load Reduction Project, FY 2007

Funding

DOE: $270K WFO: 3M $48K Sage Electrochromics $20K Delphi $14K SAE $46K

EPA $25K

Key Accomplishments Modeling and Analysis

1. Converted the integrated vehicle thermal anal ysis process to use FLUENT CFD software.
2. Estimated the impact of reducing the thermal load on A/C thermal load on A/C system capacity of a Cadillac STS as part of the improved Mobile Air Conditioning Cooperative Research Program (summer 2006 vehicle data).
3. Updated the NREL A/C fuel use analysis methodology of India with improved boundary conditions and assumptions from Indian automobile experts with EPA funding.
4. Generated a CFD mesh of a HMMWV and FMTV.

5. Calculated the A/C fuel use of a secondary loop HFC-152a A/C system.

Testing

1. Thermal soak tested a 3M solar reflective film on a Class 8 truck in Phoenix.
2. Used ADAM and Manikin Environmental Chamber to evaluate current and proposed thermal blankets to reduce or prevent hypothermia in patients during transport - collaboration with the U.S. Army Aeromedical Research Laboratory (USAARL).

Technical Papers

1. Chaney, L.; Thundiyil, K.; Chidambaram, S.; Abbi, Y.P.; Andersen, S. "Fuel Savings and Emission Reductions from Next-Generation Mobile Air Conditioning Technology in India." Eighth Vehicle Thermal Management Systems Conferen ce Proceedings; May 20-24, 2007 . Paper No. C640/085/2007. NREL Paper
No. CP-540-41154.
2. Rugh, J.; Chaney, L.; Lustbader, J.; Meyer, J.; Rustagi, M.; Olson, K.; Kogler, R. "Reduction in Vehicle Temperatures and Fuel Use from Cabin Ventilation, Solar-Reflective Paint, and a New Solar-Reflective Glazing." 2007 SAE World Congress Proceedings; April 16-19, 2007 . Paper No. 2007-01-1194.
3. Rugh, J.; Lustbader, J. "Application of a Sweating Manikin Controlled by a Human Physiological Model
and Lessons Learned." Sixth International Meeting on Thermal Manikins and Modeling (613M) Proceedings; October 17-18, 2006

. 4. Bharathan, D.; Chaney, L.; Farrington, R.; Lustbader, J.; Keyser, M.; Rugh, J. "An Overview of Vehicle Test and Analysis Results from NREL's A/C Fuel Use Reduction Research." Eighth Vehicle Thermal Management Systems Conference Proceedings ; Paper No. C640/050/2007.

Significant Presentations

1. Rugh, J. "I-MAC CRP Team 3 Advanced Thermal Management Technologies 2006 Vehicle Test Status." Presented at the I-MAC Core Meeting. December 6, 2006.
2. Rugh, J.; Chaney, L.; Meyer, J. "I-MAC Team 3 Thermal Load Reduction." Presented at the I-MAC Final Meeting. July 20, 2007.
3. Rugh, J. "Assessing the Vehicle Level and National A/C Fuel Use Impact of Advanced Climate Control Technologies." Presented at the Cooling Cars with Less Fuel – IEA Workshop. October 23, 2006.
4. Chaney, L; Thundiyil, K.; Chidambaram, S.; Abbi, Y.P.; Andersen, S. "Fuel Savings and Emission Reductions from Next-Generation Mobile Air Conditioning Technology in India." Presented at the Eighth Vehicle Thermal Management Systems Conference. May 20-24, 2007. Paper No. C640/085/2007.

5. Rugh, J.; Chaney, L.; Lustbader, J.; Meyer, J.; Rustagi, M.; Olson, K.; Kogler, R. "Reduction in Vehicle Temperatures and Fuel Use from Cabin Ventilation, Solar-Reflective Paint, and a New Solar-Reflective Glazing." Presented at the 2007 SAE World Congress. April 16-19, 2007. Paper No. 2007-01-1194.

736. Rugh, J.; Lustbader, J. "Application of a Sweating Manikin Controlled by a Human Physiological Model and Lessons Learned." Presented at the Sixth International Meeting on Thermal Manikins and Modeling (613M). October 17-18, 2006.

7. Bharathan, D.; Chaney, L.; Farrington, R.; Lustbader, J.; Keyser, M.; Rugh, J. "An Overview of Vehicle Test and Analysis Results from NREL's A/C Fuel Use Reduction Research." Presented at the Eighth Vehicle Thermal Management Systems Conference. Paper No. C640/050/2007.
8. Baker, J.; Ghodbane, M.; Rugh, J.; Hill, W. "Alternative Refrigerant Demonstration Vehicles." Presented at the 2007 SAE Alternative Refrigerant Systems Symposium. July 17, 2007, Scottsdale, Arizona.
9. Rugh, J. "SL R-152a MAC: Updated Vehicle Analysis, Impact of Increased Mass, and Impact on Idle Time." Presented at the US EPA's HFC-152a Workshop. August 14-15, 2007, Washington, D.C.

74F1147-E(09/2007) REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188

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1. REPORT DATE (DD-MM-YYYY) January 2008 2. REPORT TYPE Technical Report 3. DATES COVERED (From - To)

5a. CONTRACT NUMBER DE-AC36-99-GO10337

5b. GRANT NUMBER 4. TITLE AND SUBTITLE Vehicle Ancillary Load Reduction Project Close-Out Report: An Overview of the Task and a Compilation of the Research Results

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER NREL/TP-540-42454

5e. TASK NUMBER FC07.5000 6. AUTHOR(S) J. Rugh and R. Farrington

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) National Renewable Energy Laboratory 1617 Cole Blvd. Golden, CO 80401-3393 8. PERFORMING ORGANIZATION
REPORT NUMBER NREL/TP-540-42454

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12. DISTRIBUTION AVAILABILITY STATEMENT National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161

13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)The amount of fuel used for climate control in U.S. vehicles reduces the fuel economy of more than 200 million lightduty conventional vehicles and thus affects U.S. energy security. Researchers at the DOE National RenewableEnergy Laboratory estimated that the United States consumes about 7 billion gallons of fuel per year for airconditioning (A/C) light-duty vehicles. Using a variety of tools, NREL researchers developed innovative techniques and technologies to reduce the amount of fuel needed for these vehicles' ancillary loads. For example, they found that the A/C cooling capacity of 5.7 kW in a Cadillac STS could be reduced by 30% while maintaining a cooldown performance of 30 minutes. A simulation showed that reducing the A/C load by 30% decreased A/C fuel consumption by 26%. Other simulations supported the great potential for improving fuel economy by using new technologies and techniques developed to reduce ancillary loads.

15. SUBJECT TERMS fuel economy; light-duty vehicles; vehicle ancillary loads; vehicle air-conditioning; energy efficiency in vehicles

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