CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION

............................................................................................................. 4-1

4.2 TECHNOLOGIES THAT DO NOT AFFECT CALCULATED DAILY ENERGY

CONSUMPTION

................................................................................................................... ...... 4-2

4.2.1 Non-Penetrative Internal Racks and Shelving

........................................................ 4-2

4.2.2 Refrigeration System Override

............................................................................... 4-2

4.2.3 Air and Water Infiltr ation Sensors

.......................................................................... 4-2

4.2.4 Humidity Sensors

.................................................................................................... 4-3

4.2.5 Heat Flux Sensors

................................................................................................... 4-3

4.2.6 Automatic Evaporator Fan Shut-Off

....................................................................... 4-3

4.2.7 Hot Gas Defrost

...................................................................................................... 4-3

4.3 SCREENED-OUT TECHNOLOGIES

............................................................................. 4-4

4.3.1 Revolving Doors

..................................................................................................... 4-4

4.3.2 Fiber Optic Natural Lighting

.................................................................................. 4-4

4.3.3 Energy Storage Systems

......................................................................................... 4-4

4.3.4 Non-Electric Anti-sweat Systems

........................................................................... 4-4

4.3.5 Automatic Insulation Deployment Systems

............................................................ 4-5

4.3.6 Higher Efficiency Evaporator Fan Motors

............................................................. 4-5

4.3.7 3-Phase Motors

....................................................................................................... 4-5

4.3.8 Economizer Cooling

............................................................................................... 4-5

4.4 REMAINING TECHNOLOGIES

..................................................................................... 4-5

4-iCHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter addresses the screening analysis that the U.S. Department of Energy (DOE) conducted in support of the ongoing energy c onservation standards rulemakings for walk-in coolers and freezers (WICFs). In the mark et and technology assessm ent (chapter 3), DOE presented an initial list of technologies that can reduce the energy consumption of WICFs. The goal of the screening analysis is to screen out technologies that will not be considered further in the rulemaking analyses. Some of the technolog ies considered in chapter 3 can reduce annual energy consumption under real-world conditi ons, but may not increase the efficiency as measured under the DOE test procedure. DOE removed from consideration those technologies that do not decrease measured energy consump tion. DOE evaluated the remaining technologies using the screening criteria set forth in the Energy Policy and Conservation Act (EPCA). (42

U.S.C. 6311–6317)

Section 325(o) EPCA establishe s criteria for prescribing new or amended standards that are designed to achieve the maximum improvement in energy efficiency. Further, EPCA directs the Secretary of Energy to determine whether a standard is technologically feasible and economically justified. (42 U.S.C. 6295(o)(2)(A), as directed by 42 U.S.C. 6316(a)(1)–(3)). EPCA also establishes guidelines for determining whether a standard is economically justified. (42 U.S.C. 6295(o)(2)(B)) In view of the EPCA requirements for determining whether a standard is technologically feasible and economi cally justified, appendix A to subpart C of Title 10, Code of Federal Regulations , Part 430 (10 CFR Part 430), “Procedures, Interpretations, and

Policies for Consideration of New or Revised Energy Conser vation Standards for Consumer Products” (the Process Rule), se ts forth procedures to guide DOE in its consideration and promulgation of new or revised efficiency st andards. These procedures elaborate on the statutory criteria provided in 42 U.S.C. 6295(o) and, in part, eliminate problematic technologies early in the process of prescribing or amending an energy efficiency standard. In particular, sections 4(b)(4) and 5(b) of the Process Rule provide guidance to DOE for making a

determination whether to eliminate from considera tion any technology that presents unacceptable problems with respect to the following criteria:

Technological feasibility. Technologies incorporated in commercial equipment or in working prototypes will be considered technologically feasible.

Practicability to manufacture, install, and service. If mass production of a technology in commercial equipment and reliable installati on and servicing of the technology could be achieved on the scale necessary to serve the relevant market at the time of the effective date of the standard, then that technology will be considered practicable to manufacture, install, and

service.

Adverse impacts on equipment utility or equipm ent availability. If DOE determines that a technology has significant adverse impact on the utility of the equipment to significant subgroups of consumers, or result in the unava ilability of any covered equipment type with performance characteristics (including reliability), features, sizes, capacities, and volumes that

4-1are substantially the same as equipment generally available in the United States at the time, it

will not be considered further.

Adverse impacts on health or safety. If DOE determines that a technology will have significant adverse impacts on health or safety, it will not be considered further.

In sum, if DOE determines that a particular technology or combination of technologies

fails to meet one or more of the four criteri a, it will be screened out. Section 4.3 below documents the reasons for eliminating any technology.

4.2 TECHNOLOGIES THAT DO NOT AFFECT CALCULATED DAILY ENERGY

CONSUMPTION

As stated above, technologies that do not decr ease measured energy consumption are not

considered beneficial in the context of this ru lemaking. Therefore, DOE removed the following technologies from consideration.

4.2.1 Non-Penetrative Internal Racks and Shelving

Many manufacturers have noted that often end users will install interior shelving units and racks in the walk-ins using penetrative fasten ers such as nails and screws. These, by nature, compromise the inner metal skin and insulation of the envelope resulting in reduced insulating capacity and possibly air leakage. However, since manufacturers have little control over behavior of end-users and most shelving systems are now designed to be free-standing, this issue may be less important. In addition, the test procedure used to measure the daily energy performance of a WICF doesn’t account for any energy savings rela ted to this equipment. Consequently, DOE did not consider non-penetrative racks and shelving in the engineering analysis.

4.2.2 Refrigeration System Override

A refrigeration system override would cons ist of an option to manually shut off the mechanical refrigeration system for select periods of time, such as during the loading and unloading of product. At these times, high tra ffic results in many door openings, or the door being left open altogether. In a conventional system, the refrigeration system continues to operate in an attempt to bring the temperatur e down to the desired value. An override would prevent this, meaning that less energy would be used during these periods. However, the DOE test procedure for WICF has no provision for the tes ting of walk-ins equipped with such systems, and thus there would be no reduction in energy consumption as tested. Consequently, DOE did not consider refrigeration system override in the engineering analysis.

4.2.3 Air and Water Infiltration Sensors

Infiltration of water and/or water vapor into the envelope insulating material may lead to significant reductions in the insulating capacity of the affected regions due to the thermal conductivity properties of wa ter. This sort of infiltration may result from specific incidents, such as punctures or damage or a steady-state process occurring over a long period of time. A water

4-2condensate or vapor sensor, implanted within the insulating material would allow for early detection of damage to the insulating material. However, while the data may be useful for endusers and manufacturer, the technology doesn’t directly result in a reduction in energy consumption. Consequently, DOE did not consider air and water sensors in the engineering analysis.

4.2.4 Humidity Sensors

Humidity of the air is another factor wh ich can influence the performance of the mechanical refrigeration system. As more humid air has a higher enthalpy, it thus requires more energy to cool the air on a day with high humidit y. Sensors installed in the system could provide real-time information regarding the outside humidity, which would allow for more informed decisions to be made regarding topics such as the loading and unloading of product at certain times. However, these sensors (except if they are used for the purposed of anti-sweat heater control) do not provide a means of directly reducing energy consumption. Consequently, DOE did not consider humidity sensors in the engineering analysis.

4.2.5 Heat Flux Sensors

For the same reasons as the humidity sens ors mentioned above, DOE did not consider heat flux sensors in the engineering analysis.

4.2.6 Automatic Evaporator Fan Shut-Off

This control would automatically shut off ev aporator fans whenever the walk-in door is opened. The result would be that less chilled air would be blown out into the surroundings, meaning that less energy would be needed to bring the interior space back down to temperature following a door opening. However, the proposed DOE test procedure contains no provision for calculating energy savings that would occur with such a system because th e envelope (including doors) and the refrigeration system are tested se parately. Consequently, DOE did not consider automatic evaporator fan shut-off in the engineering analysis.

4.2.7 Hot Gas Defrost

Hot gas defrost utilizes heat generated from the system in order to defrost the evaporator coil rather than using a dedicated electric defrost coil. However, operation of a hot gas defroster requires that the compressor a nd fans continue to run, meanin g that the entire mechanical refrigeration system is still operating. Generally, these components collectiv ely require an energy input that is greater than that needed to operate an electrical defroster. This means that hot gas defrost would not greatly affect energy consumption as measured under the test procedure. Additionally, the test procedure contains no provision for testing a system connected to a remote rack which utilizes hot gas defrost. Consequently , DOE did not consider hot gas defrost in the engineering analysis.

4-34.3 SCREENED-OUT TECHNOLOGIES

This section addresses the technologies that DOE screened out because they did not meet the requirements of sections 4(a) and 5(b) of the Process Rule. DOE considered the following four factors: (1) technological feasibility; (2) pr acticability to manufacture, install, and service; (3) adverse impacts on equipment utility to consumers; and (4) adverse impacts on health or safety. The technologies that were screened out are: higher efficiency evaporator fan motors, external heat rejection, and energy storage systems.

4.3.1 Revolving Doors

A provision for the reduction of losses from door opening would be the use of revolving doors. Like vestibule entries, revolving door sy stems are commonly used for the entryways of large buildings. Similarly, they prevent direct exchange of air and reduce the rate of infiltration compared to a standard door. By reducing direct air exchange the associated energy savings are quite significant.

However, in order to prevent the utility of a walk-in from being impacted, the size of the door must accommodate a person plus space for ca rrying or moving products into the walk-in. Doors of this size do exist but are prohibitively expensive for medium to small sized units. In addition, these type of doors require a large foot print, reducing useable floor area for storage or other use. For these reasons, DOE did consider revolving doors in the engineering analysis.

4.3.2 Fiber Optic Natural Lighting

Fiber optic lighting systems are in use in the building industry. However, in this analysis, DOE has not encountered any such systems either in prototype or manufactured and sold for walk-in operations. As a result, DOE screened out fiber optic natural lighting on the grounds of technological infeasibility.

4.3.3 Energy Storage Systems

One proposed technology included the incor poration of thermal storage media which could be cooled during the overn ight hours and then used to lessen the refrigeration load during the peak daytime operating period. However, in th is analysis, DOE has not encountered any such systems either in prototype or manufactured a nd sold for walk-in operations. As a result, DOE screened out energy storage systems on th e grounds of technological infeasibility.

4.3.4 Non-Electric Anti-sweat Systems

While it is technically possible to perform door heating with non-electric primary energy resources, DOE has not encountered any such sy stems either in prototype or manufactured and sold for walk-in operations. As a result, DOE screened out fiber optic natural lighting on the grounds of technological infeasibility.

4-44.3.5 Automatic Insulation Deployment Systems

A system that enhanced the insulation of glass display doors during non-business hours would significantly reduce energy consump tion without impacting utility of the walk-in. However, in this analysis, DOE has not encountered any such systems either in prototype or manufactured and sold for walk-in operations. As a result, DOE screened out automatic insulation deployment systems on the gr ounds of technological infeasibility.

4.3.6 Higher Efficiency Evaporator Fan Motors

The provisions of EISA mandate that WI CF evaporator fans be equipped with electronically commutated motors (ECMs). In this analysis, DOE has not encountered any electric motor technologies which perform more efficiently than the EC Ms already required for this application. As a result, DOE has screened out the possibility of using higher efficiency evaporator fan motors on the grounds of technological infeasibility.

4.3.7 3-Phase Motors

3-phase motors can save energy over single-phase motors; however, use of 3-phase motors requires 3-phase power. No t all businesses that use walk-i ns are equipped with 3-phase power, and therefore must use single-phase equi pment. DOE screened out this design option on the grounds of utility.

4.3.8 Economizer Cooling

Economizer cooling consists of directly venting outside air into the interior of the walk-in

when the outside air is as cold as or colder than the interior of the walk-in. This relieves load on the refrigeration system when pull-down load is necessary. However, this presents a utility issue, as ambient temperatures in some areas of the country rarely or never reach temperatures as low as those inside a walk-in. Because the utility of this technology is constrained by the walk-in’s location or region, DOE screened out economizer cooling as a design option for improving the energy efficiency of walk-in coolers and freezers.

4.4 REMAINING TECHNOLOGIES

After eliminating those technologies that do not decrease energy consumption as measured by the test procedure, and do not meet the requirements of sections 4(a) and 5(b) of the Process Rule, DOE is considering the following technologies:

• Improved wall, ceiling, and floor insulation

• Improved door gaskets and panel interface systems

• Electronic lighting ballasts and high-efficiency lighting

• Occupancy sensors

• Automatic door opening and closing systems

• Air curtains

4-5• Strip curtains

• Vestibule entryways

• Display and window glass system insulation performance

• Anti-sweat heater controls

• No anti-sweat systems

• Ambient subcooling

• Higher-efficiency compressors

• Evaporator fan control

• Evaporator and condenser fan blades

• Higher-efficiency condenser fan motors

• Improved evaporator and condenser coils

• Defrost controls

• Floating head pressure

4-6