7-i CHAPTER 7. ENERGY USE ANALYSIS

TABLE OF CONTENTS

7.1 INTRODUCTION .............................................................................................................. 7-1 7.2 OVERVIEW OF ENERGY USE ANALYSIS BY EQUIPMENT CLASS ...................... 7-1 7.2.1 Simulation Tool Description ................................................................................... 7-2 7.2.2 Building Models...................................................................................................... 7-2 7.2.2.1 Modular Classroom Simulation Model ....................................................... 7-2 7.2.2.2 Modular Office Simulation Model.............................................................. 7-3 7.2.2.3 Telecommunication Shelter Simulation Model .......................................... 7-3 7.2.3 Equipment Modeling .............................................................................................. 7-5 7.2.4 Simulated Climates and Weather Data ................................................................... 7-7 7.2.5 Energy Use Extraction and Aggregation to State Level Data ................................. 7-7 7.2.6 Calculation of Gas Heating Impact ......................................................................... 7-9 7.3 ENERGY USE ANALYSIS RESULTS ........................................................................... 7-10 REFERENCES .......................................................................................................................... 7-12

LIST OF TABLES

Table 7.2.1 Development of Condenser- Only COP Values by Efficiency Level ....................... 7-7 Table 7.2.2 Calculation of UEC for Office Building in Atlanta, GA .......................................... 7-8 Table 7.3.1 National UEC Estimates for SPVAC and SPVHP Equipment ............................... 7-11

LIST OF FIGURES

Figure 7.3.1 Baseline National Unit Energy Consumption Estimates by Building Type .......... 7-107-1 CHAPTER 7. ENERGY USE ANALYSIS

7.1 INTRODUCTION

The e nergy use analysis discusses the process used by the U.S. Department of Energy (DOE) to provide energy use estimates for baseline and higher- efficiency standard levels for single package vertical air conditioners (SPVAC) and heat pumps (SPVHP), collectively referred
to here as single package vertical units (SPVU ).

This chapter describes the energy use analysis for SPVAC and SPVHP equipment with a cooling capacity less than 135,000 British thermal units per hour (B tu/h ). Th is chapter detail s the determin ation of baseline annual per unit energy consumption (UEC) estimates for each equipment class and describes the development of UEC estimates for more

- efficient equipment, up to the maximum technolog ically feasible (max

- tech ) levels defined in chapter 5 of the technical support document (TSD)

.
For each of these equipment types, the existing or proposed Federal standard is expressed

as an efficiency metric or metrics : e nergy e fficiency r atio ( EER ) for cooling efficiency and

c oef f icient of p erformance (COP) for heating efficiency. For each equipment class, this chapter describes how an estimate of the UE C is developed corresponding to the different rated efficiencies

.

7.2 OVERVIEW OF ENERGY USE ANALYSIS BY EQUIPMENT CLASS

T he analysis to assess the UEC of SPVAC and SPVHP equipment began with a review of the existing market and applications for the various classes of equipment

. The market assessment indicat ed that for SPVU equipment , the market is primarily modular buildings characterized as education (i.e. , modular classrooms), modular offices, and what are commonly referred to as technical or telecommunica tion shelters

— small

, self -contained building structures housing electronic equipment but not intended for occupants. DOE analyzed the energy consumption of SPVU equipment using a building simulation approach for three classes of commercial buildings: modular classrooms, modular offices, and telecommunication shelters

. To estimate the energy use of SPVAC and SPVHP equipment in these building types, DOE developed building simulation models for use with DOE’s EnergyPlus software. 1 In each case, the build ing construction elements ( e.g. , footprint, window- wall ratio, envelope construction, and general building form factor and design) were developed to be representative of typical building designs within the general class of building being modeled . The build ing simulation models were configured to use heating, ventilating, and air-conditioning ( HVAC ) systems representing SPVAC or SPVHP equipment and were modeled in a diverse set of climates and for the range of efficiency levels developed in the engineering a nalysis

.

H eating, cooling , and supply blower energy use from each simulation was scaled by the ratio of representative cooling capacities analyzed in the rulemaking to the simulated equipment capacit ies for each building modeled. This provides climate -spe cific UEC statistics for the representative cooling capacities developed in the engineering analysis (36,000 Btu/h and 72,000 Btu/h) for each building type. These c limate

- sp ecific energy use results were weighted to provide7-2 state

- level UEC estimates by building type and equipment class

. These state

- level estimates were provided to the subsequent life- cycle cost (LCC) analysis.

7.2.1 Simulation Tool Description

DOE used the EnergyPlus version 8.0 software for the energy use analysis. EnergyPlus predicts the energy use of a building given hourly weather file data , a description of the building and the operation of the building, estimated internal loads, and a characterization of the building HVAC equipment. Energy use results for the building can be readily extracted for different time steps and at detailed subcomponent levels if necessary. EnergyPlus is an integrated software tool, where both the building loads and how those loads are served by equipment are solved iteratively. EnergyPlus has a sepa rate, but robust, ground heat transfer model, which is particularly useful in the simulation of smaller buildings. DOE is currently using EnergyPlus as the basis for most of its whole-building energy simulation research, and the tool and its ongoing develo pment are actively supported within DOE.

7.2.2 Building Models

A prototypical building model was developed for each building type and is described by the building footprint, general building size and design, and internal gains and operating schedules

. A descript ion of each building model is provided below, with further details, including operation schedules, found in appendix 7A. These three building models (modular classroom, modular office, telecommunication shelters) were used to establish the energy usage of SPVAC and SPVHP equipment used in the aforementioned building markets.

7.2.2.1 Modular Classroom Simulation Model

To estimate the energ y consumption of SPVAC and SPVHP equipment in a classroom application, DOE developed a double wide (56 ft by 28 ft), single story, 1,568- ft 2 wood- frame modular classroom simulation model . Wood-frame construction was chosen because it is consistent with known modular classroom design. A crawlspace was used to represent the above

ground floor level construction characteristic of these buildings . A window- to

- wall area fraction of 15 percent was used as representative of typical modular classroom construction. Envelope performance characteristics were established using the requirements in ANSI/ASHRAE/IESNA a 90.1-2004 to approximate a mix of existing stock and new construction. 2 Schedules and load profiles were taken from classroom -space building zones in the DOE primary school commercial prototype building models. 3 These schedules represent a building used as a classroom effectively 10 months of the year, with light (but daily) usage during a 2 -month summer period. Internal loads fo r receptacle (plug) loads were based on direct equipment power (watts per square foot) figures for the DOE primary school commercial prototype building model and were set to 1.4 W /ft 2 peak . Occupancy loads were also developed from the DOE primary school co mmercial prototype building and were set to 25 persons per 1,000 ft 2 . Lighting power and internal loads were based on ASHRAE 90.1-2004 lighting power density levels for classroom space at 1.4 W /ft 2 peak, which was selected to be representative of a mix of existing classroom lighting power in the building stock and in recent construction. Ventilation levels were based on the

a ANSI is the American National Standards Institute; ASHRAE is the American Society of Heating, Refrigerating, and Air

- Conditioning Engineers; IESNA is the Illuminating Engineering Society of North America.7-3 requirements of ASHRAE Standard 62.1-2004, which reflects current ventilation requirements in many building codes and would be appropri ate for most new or replacement equipment

. Mechanical ventilation was set at 0.37 c ubic feet per minute (c fm ) /ft 2 for the classroom based on ASHRAE 62.1 -2004 requirements. The HVAC equipment was scheduled to operate the supply fan 14 hours a day during weekdays to provide both ventilation and circulation during occupied periods. It was scheduled off during weekends and holidays.

Infiltration was modeled using the EnergyPlus Airflow Network model, which provides for a wind - and temperature

- based estimate of infiltration loads during the year that also responds to HVAC system operation. An equivalent leakage area for the building was first established using an overall air exchange rate of 7 air changes per hour (ACH) under a 50- pascal indoor-outdoor pressure difference

. This equivalent leakage area was then spread evenly among the walls, floor, and ceiling components. The 7 ACH value was selected as generally representative of range of reported ACH values from different studies. 4 5 6

Economizer requi rements by location were established consistent with those in ASHRAE 90.1-2004 for equipment less than 65,000 Btu/h, and separately for equipment greater than or equal to 65,000 Btu/h, with both sets of economizer requirements being simulated to help estab lish the typical energy use per ton for equipment in these different size categories.

7.2.2.2 Modular Office Simulation Model

To estimate SPVU energy use in an office type application, DOE developed a 1,568- ft 2 (56

- ft by 28

- ft) wood- frame modular office simulation model similar in general design to the modular classroom model. A principal difference between the models is in the use of office type load and usage profiles for the modular office application. Schedules and load profiles as well as internal l oad estimates were all based on DOE’s small office commercial prototype building model. 3 Internal receptacle loads were set to 0.63 W /ft 2 peak

. Peak scheduled occupancy was set to 5.6 persons per 1,000 ft 2 . Lighting power requirements were based on ASHRAE 90.1-2004 requirements for office space

, selected to be representative of a mix of lighting power in the building stock and in recent construction, at 1.0 W /ft 2 peak

. Air

- side economizer requirements were established consistent with those in ASHRAE 90.1-2004 for SPVU equipment less than 65,000 Btu/h, and separately for SPVU equipment greater than or equal to 65,000 Btu/h, with both sets of requirements being simulated to help establish the typical energy use per ton for SPVU equipment in both size ca tegories . The HVAC equipment was scheduled to operate the supply fan 13 hours a day during weekdays and 12 hours on Saturday during occupied periods. It

was scheduled off Sundays and holidays.

7.2.2.3 Telecommunication Shelter Simulation Model

Telecommunication sh elter s are used to house electronic components like phone switches, optical fiber networking equipment , transmitters

, and receivers in remote locations
away from a central telecommunication office

. These shelters protect the equipment from humidity, dust, solar overheating, and physical damage. As the housed electronic equipment generate s heat during operation, there is a need to maintain the air temperature inside the shelter within certain limits. To estimate SPVAC energy use in a typical technical/telecommunication shelter, DOE developed a small telecommunication shelter model in the form of a 240- ft 2 precast7-4 concrete wall and roof shelter (12 ft by 20 ft)

. b The telecom munication shelter used continuous interior R-10 foam insulation in roof, floor, and wall assemblies

. The pre-fab building was mounted on a concrete slab in all climates simulated as is typical commercial practice

. For the telecommunication shelter, DOE did not identify a source for typical representative internal electronic loads as a function of building size and did not find substantial information on representative internal gain profiles. However , based on discussions with shelter retailers, DOE used a 10.55-kW (36,000-Btu/h) maximum internal load to reflect intern al design load in the shelter

. DOE determined that on average over the year, this internal load ran at a constant 65 percent of peak internal load , reflecting estimates for computer server environments. 7 A study of options for improving energy efficiency in the telecommunications ( e.g. , cellular phone) network notes that power consumptio n for electronics in many shelters is often fairly stable from day to night and largely independent of phone traffic. However, an available o perating strategy that consists of turning certain radio transmitters and receivers off when the call traffic decreases can provide up to a 40 percent reduction in power consumption during these periods. 8 Lacking further detail, DOE used a constant average thermal load of 6.86 kW (23,400 Btu/h), which did not change with time of day. However, equipment sizing was based on the maximum internal load level plus design day environment loads in each climate. DOE did not add an additional cooling sizing factor for the telecommunication shelter model as this was reflected in the underlying computer server data defining the average internal load

. Lighting power was not explicitly modeled as its use would be expected to be minimal.

The high internal load density an d the insulated building envelope in the telecom munication shelter resul t in year round cooling loads. To reduce energy consumption, air side economizers represent a means to reduce the cooling load in tele communication shelters

. Discussion with different shelter retail and manufacturin g firms indicated a wide variation in whether economizers are typically specified by the individual telecom munication firm
customers . W hile some shelter manufacturer/retailers indicated climate variation in how these

are spec ified

, c d others suggested it is often driven more by individual corporate user specification s. b A voluntary standard for telecommunication site development, Motorola R-56, suggests that all wall -mount HVAC units should be equipped with economizers. 9 However, discussion with manufacturer contacts during the engineering analysis suggested that overall only approximately 45 percent of SPVU equipment is shipped with an economizer option for the telecommunication market

. These data were not available by equipment capacity. As a consequence, DOE simulated the telecommunication building in each location with and without an economizer option and provided both sets of results as inputs to the LCC analysis, where they could be appropriately sampled using the es timated market fraction with and without an economizer

. The HVAC equipment is scheduled to operate in a fan cycling mode during all hours. In this mode, the fan will operate only for the duration of time tha t the SPVAC compressor operates

b Typical shelter and peak equipment load based on Pacific Northwest National Laboratory (PNNL) communication with staff at Midwest Surplus, a retailer of new and refurbished communication shelters (May 18, 2012).

< http://www.midwestsurplus inc.com/contactus.php >

c Discussion between PNNL staff and Thermobond staff (July 3, 2012). < http://www.thermobond.com > d Phone discussion with PNNL and CellXion staff (Aug 1, 2012). < http://sabrebuildingsystems.com >7-5 to serve the space conditioning loads, or in the event that the load is met through economizer cooling.

7.2.3 Equipment Modeling

Equipment performance characteristics used in modeling are shown in appendix 7A. Each building model was simulated using one HVAC unit for the building, responding to a single space thermostat . I n the case of the telecommunication shelter, redundant identical air conditioners with alternating usage during the year were assumed when establishing average annual energy consumption per unit. The use of redundant air -conditioning units was consistent with industry practice based on communication with shelter manufacturers e f as well as the Motorola R-56 guideline. To provide for this, the energy use per unit established for the equipment serving teleco mmunication shelter s was calculated by dividing the energy use per ton for the simulated buildings by 2 and then multiplying by the representative capacity in tons for each equipment class.

Simulations were done for the buildings using SPVAC equipment with electric resistance heating, and then a separate set of simulations was done for buildings with SPVHP equipment. For each equipment class and building type combination, DOE simulated each efficiency level identified in the engineering analysis

. Supply air fan/ blower power at the base line efficiency level was based on review of manufacturer literature and reported blower motor voltage and current data for 3 -ton SPVAC equipment at a 9.0 energy efficiency r atio ( EER ) level and using a permanent

- split capacitor ( PSC ) motor. 10 The fan power data were not available, so a power factor of 0.9 was used to convert available blower motor volt- amps to watts . The corresponding fan power was estimated to be 154.4 watts per cooling ton (W/ton). Based on data develo ped in the engineering analysis, the energy analysis used PSC motors at this power level for EER values up to 9.5. Electronically commutated supply air fan motors were assumed for equipment with an EER of 10.0 and higher to reflect the engineering analysis assumptions. Direct fan power data

were not available from manufacturer literature for fans using electronically commutated (brushless direct current ) motors (ECM) . An estimate of the fan power for systems using an ECM fan motor was made based on the rati o of typical motor efficiency for fractional (1/3) h orsepower (h p) PSC and ECM motors. g The resulting ECM motor horsepower was estimated
at 113.6 W /ton . Fan motors were assumed to run at constant speed and constant power while operating and d id not reduce speed as a function of thermal load. h

Equipment cooling EERand heating COP were converted to corresponding condenseronly cooling COP and condenser-only heating COP simulation inputs for each efficiency level simulated for the nominal 95 °F and 47 °F outdoor temperature rating conditions, respectively.

e Typical shelter and peak equipment load based on Pacific Northwest National Laboratory (PNNL) communication with staff at Midwest Surplus, a retailer of new and refurbished communication shelters (May 18, 2012).

< http://www.midwestsurplusinc.com/contactus.php > f Discussion between PNNL staff and Thermobond staff (July 3, 2012). < http://www.thermobo nd.com >
g Nominal PSC motor efficiency is estimated at 0.54 and nominal ECM fan motor efficiency is estimated at 0.725. Adjusting for the benefit of the fan heat reduction and greater net capacity yielded a supply fan power per ton ratio of 0.737 and an equivalent 113.6 W/ton for a system with an ECM blower.
h While certain high

- efficiency equipment on t he market today may utilize the benefits of variable speed fan operation, it was assumed that this would not be a required feature for equipment built to meet a standard with a full

load ( e.g. , EER) efficiency rating metric.7-6 Each of these latter two metrics is used as an input to the EnergyPlus simulation model and represent s the performance of the cooling equipment’s refrigeration component without the supply fan power and corresponding heat gain into the supply air stream. They are calculated by backing out the estimated supply fan power at nominal rating conditions from the rated energy consumption while simultaneously accounting for the effect of fan heat. This is done for the condenser-only cooling COP and condenser-only heating COP using the following equations :

COP CU

_ Cool = CAP C 3. 413 + AHRIFanPower

CAP C EER − AHRIFanPower Eq. 7.1

COP CU

_ Heat = CAP h 3. 413 − AHRIFanPower

CAP h COPx 3. 413 − AHRIFanPower Eq. 7.2

Where :

COP CU_Cool = condenser-o nly cooling COP, COP CU_ Heat = condenser-o nly h eating COP, CAP c = cooling ca pacity a t Air -Conditioning, Heating, and Refrigeration Institute ( AH RI ) rating conditions (Btu/h), CAP h = heating capacity at A H RI rating conditions (Btu/h), EER = rated energy efficiency ratio (Btu/W) at AHRI rating conditions, COP = heating rated coefficient of performance at A HRI rating conditions, and AH RIFanPower = supply fan power at AHRI rating conditions.

The estimated AH RIFanPower for equipment with PSC and ECM blower motors and the nominal rating conditions for SPVAC and SPVHP equipment as discussed above were used to develop the condenser-only cooling and heating COP values. The calculated COP CU_Cool and COP CU_Heat are shown in Table 7.2.1 for each EER and COP combination developed in the engineering analysis

. Capacity and efficiency performance curves as a function of indoor and outdoor conditions representative of SPVAC and SPVHP equipment were developed for this simulation analysis and are provided in appendix 7A.7-7 Table 7.2.1 Development of Condenser -O nly COP Values by E fficiency L evel

Efficiency Level EER COP * AHRIFanPower W/ton COP CU_Cool COP CU_Heat *

EPCA ** Baseline 9.0 3.0 154.4 3.113 3.303 ASHRAE Baseline 10.0 3.0 113.6 3.341 3.214
1 † 10.5 3.2 113.6 3.526 3.453
2 † 11.0 3.3 113.6 3.714 3.574
3 † 11.75 3.9 113.6 3.999 4.317
4 † 12.3 3.9 113.6 4.211 4.317
* Heat pumps o nly.

** EPCA is the Energy Policy and Conservation Act of 1975, as amended by the Energy Independence and Security Act of 2007. † Efficiency Level applies to SPVAC <65,000 Btu/h and SPVHP <65,000 Btu/h equipment classes only.

7.2.4 Simulated C limat es and W eather D ata

DOE used typical meteorological year (TMY3) weather data for each of 237 location s for the EnergyPlus simulations. 11 The locations correspond to 237 U.S. climate locations for which DOE had previously generated state weighting factors . DOE sized equipment for each building simulation using a design -day sizing approach incorporating the design data found in the EnergyPlus design

- day weather data files for each location

. i DOE also incorporated an additional cooling sizing factor of 1.1 for the equipment used in the modular office and modular classroom simulations, reflective of the typical sizing adjustment needed to account for discrete available equipment capacities in SPVAC and SPVHP equipment. As stated earlier , DOE did not incorporate additional sizing factors for the telecommunication equipment

.

7.2.5 Energy Use Extraction and Aggregation to State Level Data

From the annual simulation results for buildings using SPVAC and SPVHP equipment in each climate

, DOE extracted the condenser energy use for cooling, the supply air blower energy use for both heating and cooling hours, the electric resistance heating energy, and the equipment capacity for each building type, climate, and efficiency level

. DOE developed corresponding normalized annual cooling energy per cooling ton and annual blower energy per cooling ton for the SPVAC equipment at the efficiency simulated by dividing the annual energy use data for each end

- use by the total building cooling capacity in tons. In addition, the normalized el ectrical heating energy per ton was calculated b y dividing the electrical heating energy use by the total building cooling capacity in tons for the building. In the ca se of SPVAC equipment, this per-ton heating energy use was based on electric resistance heating . In the case of SPVHP equipment, this per-ton heating energy was based on the sum of the compressor heating energy and the electrical resistance heating energy provided

. The per -ton cooling, fan, and heating energy use were then individually aggreg ated to
state

- level estimates

. For each state

, relative weighting factors associated with each TMY location were used based on previously developed climate weights . DOE used population- based weighting factors developed for each of the 237 TMY climate s base d on detailed population

i EnergyPlus TMY3

- based weather data files and design day data files available at:

< http://apps1.eere.energy.gov/buildings/energyplus/weatherdata_about.cfm >7-8 statistics from the U.S. Geological Survey ( USGS ) Populated Places dataset to weight each climate in each state. The development and documentation of these weighting factors is found in appendix 7B. The original weight ing factors were developed based on 239 TMY2 12 locations. As DOE used the more recent TMY3 weather files for the energy simulations, DOE first identified all TMY2 locations with a corresponding TMY3 weather file. DOE did not include the TMY2 island locations of San Juan

, Puerto Rico , and Guam in the development of s tate

- level data

, which reduced the data set to 237 locations for this analysis

. For each combination of equipment class, building type, climate, and efficiency level, DOE developed per-ton cooling, blower, and heating annual energy consumption values for each simulation by location , and aggregated these to corresponding s tate values using the previously discussed weighting factors to establish the contribution of each climate to each s tate

. Once developed at the s tate level, these per -ton energy end- use estimates were multiplied by the representative cooling capacity estimated for the equipment class being modeled (3 or 6 tons). This provided state -average cooling, blower, and heating annual energy consumption for both equipment sizes.

To be consistent with the energy uses typically associated with air -conditioning equipment and reported in other rulemaking analyses , DOE based the energy use for SPVAC equipment on cooling and fan energy only and did not include total heating energy in the overall UEC . However, the analysis indicated that where fan power was reduced for higher efficiency levels (10 EER and above), there was a corresponding non- trivial increase in the amount of heating required in each climate to make up for the loss of heat energy imparted into the supply air stream through the use of the more- efficient supply air blower during the heating season. The scale of this impact was climate dependent, with little heating impact in warm climates, and greater heating impact in cold climates where space heating requirements dominate during the
year . To account for this heating energy impact, for each climate

, DOE calculated a heating “take back” effect for higher efficiency levels as a dev iation from the baseline heating energy use per ton for each SPVAC equipment capacity and efficiency level

. The final SPVAC energy consumption estimates were then based on the calculated cooling and supply blower energy uses plus this heating “take back,” which allowed the energy savings estimates to correctly account for the heating energy increase during the year that occur s at certain high efficiency levels when using higher efficiency blower motors.

An example of the impact of the heating take back is shown below for a modular office in Atlanta, Georgia

, for a 3 -ton SPVAC unit at the ASHRAE baseline efficiency level relative to the EPCA baseline level using the data shown in Table 7.2.2

.

Table 7.2.2 Calculation of UEC for Office Building in Atlanta , GA Cooling Energy

kWh/yr

- ton Blower Energy kWh/yr

- ton Heating Energy kWh/yr

- ton Total Energy kWh/yr

- ton EPCA Baseline 1

, 091 600 4

, 294 5
, 986 ASHRAE Baseline 992 455 4, 364 5, 812
Heating Take B ack 707-9 UEC_SPVAC i,j = (Cooling_energy_per_ton i,j + Blower_energy_per_ton i,j + Heating _t akeback _per_ ton i, j ) × Representative Capacity (t ons) Eq. 7.3

Where :

Cooling_energy_per_ton i, j = Cooling_energy_per_ton for climate i at efficiency level j

, Blower_energy_per_ton i,j = Blower_energy_per_ton for climate i at efficiency level j , and Heating_takeback_per_ton i,j = Heating_energy_per_ton for climate i at efficiency level j –

H eating_energy_per_ton for climate i at the baseline efficiency level

. Using Eq. 7.3

, the SPV AC UEC for 3 -ton cooling equipment used in modular offices in Atlanta at the ASHRAE baseline is as follows.

UEC_SPVAC Atlanta, ASHRAE Baseline = [9 92 kWh/yr-ton + 455 kWh/yr-ton + (4,364 kWh/yr-ton – 4,294 kWh/yr-ton)] × 3 tons

UEC_SPVAC Atlanta, ASHRAE Baseline = 4,551 kWh/yr Eq. 7.4

The analysis method for SPVHP equipment included the heating energy (compressor heating and electric resistance backup) directly from the simulat ion results in developing the UEC by climate , and thus DOE did not separately calculate a heating “take back” effect.

The results of the steps described above, taken for each building type and equipment class, provided the annual expected energy consumption for each SPVAC or SPVHP class for each combination of building type, climate, and efficiency level.

Once s tate

- level UEC estimates for each equipment class were established, they were provided to the LCC analysis

. National average UEC estimates for each equipment class and efficiency were also established based on population- based weighting across states and shipment weights to the different building types. See chapter 8 of the notice of proposed rulemaking ( NOPR ) TSD for discussion of weighting across states and building types. With regard to the latter, while DOE established shipment weights for SPVAC equipment to three building types (education, office, and telecommunication), DOE determined that SPVHP equipment was not used to a sig nificant extent in telecommunication facilities and thus only allocated shipments of SPVHP equipment to two building types: education and office.

7.2.6 Calculation of Gas Heating Impact

Based on discussions with manufacturers in the engineering model development , it was estimated that approximately 5 percent of the market for the SPVAC less than 65,000 Btu/h class utilize s gas furnace heating, and thus the corresponding heating take back is an effect on gas heat consumption. To account for this, DOE multiplied t he heating take back for the simulated SPVAC equipment, based on electric resistance heat, by the ratio of the electric resistance heat generation efficiency (assumed 100 percent) to an assumed gas heating efficiency

. The gas7- 10 heating efficiency was based on an estimated 81 percent furnace annual fuel utilization efficiency

. The gas heating take back was then converted to annual thousand British thermal units (kBtu) of natural gas for monetizing the purchases in the LCC.

7.3 ENERGY USE ANALYSIS RESULTS

Figure 7.3.1 shows the national average EPCA baseline UEC estimates for each equipment class by build ing type assuming electric heat and based on the state population weights discussed in chapter 8 of the NOPR TSD

. UEC for SPVAC equipment includes cooling
energy and supply fan energy only

. UEC for SPVHP equipment includes cooling, supply fan, and heating energy consumption. SPVHP heating energy use resu lts in much higher UEC figures than SPVAC equipment for both modular classrooms and offices. For the telecommunication shelters modeled, internal gains provide essentially all the heating energy needed for the buildings within the defined control temperature range. As such, no heating energy use is seen in the models, and SPVAC and SPVHP UEC figures are the same for the same capacity equipment. In addition, for modular offices and classrooms, the 6- ton equipment uses slightly less than twice the energy as the 3 -ton equipment at the baseline efficiency level for both equipment types. While 6 -ton baseline units have a lower EER than 3-ton baseline units (8.5 vs. 8.9), they also benefit from greater use of economizers in the analysis

. By contrast, the UEC estim ate for baseline 6 -ton units serving the telecom munication shelters is slightly more than twice that of the 3- ton telecom munication unit due only to the difference in baseline EER for the two sizes

.

Figure 7.3.1 Baseline National Unit Energy Consumption Estimates by Building Type7- 11 Table 7.3.1 shows the national average annual U EC estimates for SPVAC and SPVHP equipment corresponding to the EER and COP levels analyzed, when weighted across building types, states , and heating fuel types . These estimates presume shipments for SPVAC equipment to education, office, and telecommunication sectors at 35 percent , 30 percent , and 35 percent, respectively

, of the entire market for SPVAC equipment, as detailed in chapter 9 of the NOPR TSD . For SPVHP equipment, DOE presumed that heating energy needs were such that telecommunication shelter manufacturers would not purchase SPVHP equipment. As such, shipment weightings for SPVHP equipment were apportioned only to the education and office building use categories at 54 percent and 46 percent, respectively

. See chapter 9 of the NOPR TSD for details

. UEC estimates by state for each equipment class are found in the LCC analysis spreadsheet tool, and are discussed in chapter 8.

Table 7.3.1 National UEC Estimates for SPVAC and SPVHP Equipment

Ef ficiency Level Equipment Class

SPVAC <65 kBtu /h SPVHP <65 kBtu/h SPVAC, ≥ 65 and <135 kBtu/h SPVHP ≥65 and <135 kBtu/h
kWh/yr Gas kBtu/yr * kWh/yr kWh/yr kWh/yr

EPCA Baseline 6,880

- 20,921 13,743 41,721 ASHRAE Baseline ** 6,175 5 4 20,383 12,251 40,589 Level 1 5,923 5 4 19,921 NA NA Level 2 5,694 5 4 19,629 NA NA Level 3 5,387 5 4 18,775 NA NA Level 4 * * 5,185 5 4 18,633 NA NA

* Calculated average gas heating “take back” per unit based on 5 percent of market with gas heat.
** ASHRAE b aseline represents max

- tech levels established for SPVAC and SPVHP equipment greater than or equal to 65,000 Btu/h, but less than 135,000 Btu/h . Level 4 represents max

- tech levels established for SPVAC and SPVHP equipment less than 65,000 Btu/h.7- 12 REFERENCES

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– Office of Energy Efficiency and Renewable Energy. EnergyPlus Energy Simulation Software V 5.0 . (Last accessed April 24, 2013.)

< http://apps1.eere.energy.gov/buildings >

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. American Society of Heating, Refrigerating and Air -Conditioning Engineers, Atlanta, Georgia.

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< http://www.energycodes.gov/development/commercial/90.1_models >
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