Conference Paper

NREL/CP-550-48295

August 2010

Walmart Experimental Store 

Performance Stories

Preprint

Michael Deru, Eric Kozubal, and Paul Norton

Presented at ACEEE Summer Study

Pacific Grove, California

August 15–20, 2010
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1

Walmart Experimental Store Performance Stories

Michael Deru, Eric Kozubal, and Paul Norton, National Renewable Energy Laboratory

ABSTRACT

Walmart opened two experimental stores—one in Colorado and one in Texas—in 2005 to 

serve as test beds for several advanced building systems. Each store embodied more than 50 

experiments covering materials, water systems, energy systems, and renewable energy 

production. Walmart worked for three years with the National Renewable Energy Laboratory for 

the Colorado Store and Oak Ridge National Laboratory for the Texas store to monitor, analyze, 

and report on their performance. This paper presents the performance of the energy system in 

the Colorado store. 

HVAC experiments included waste oil boilers, a microturbine/absorption chiller 

combined heat and power system, evaporative cooling, and a transpired solar collector. The 

refrigeration systems integrated a medium-temperature secondary loop, evaporatively cooled 

condenser, doors on medium-temperature cases, and light-emitting diodes on cases. Experiments 

in the lighting systems included a redesigned roof for clerestory daylighting and T-5 fluorescent 

lamps. Three photovoltaic systems for a total of 135 kW and a 50-kW wind turbine are also 

included.

The energy system performance was compared to the measured performance of a 

prototypical Walmart store and to other benchmarks where appropriate. Many worked well and 

continue to save energy. Some did not perform well and have been altered, or have been 

removed and replaced with other systems. Many lessons learned have been incorporated into the 

prototype design and help Walmart save energy in new stores. The revised systems have been 

monitored for the past year and show excellent energy performance.

Introduction

Walmart has stated that it is committed to environmental responsibility, and that it wants 

to be a leader in building and operating retail facilities that minimize the use of energy and 

natural resources. Since 1993, Walmart has constructed a series of experimental stores designed 

to test technologies and techniques for reducing its buildings’ energy and environmental impacts. 

Walmart continued this effort with the construction of two experimental supercenters—one in a 

hot climate (McKinney, Texas) and one in a cold climate (Aurora, Colorado) (see Figure 1). 

Each supercenter incorporated a wide range of advanced efficiency technologies to reduce its 

energy needs and employ solar and wind energy generated on site to meet some of the remaining 

energy needs. The two experimental stores were meant to be test beds for innovative 

technologies and employed mixes of “experiments” appropriate for the different climates.

The performance of these stores was monitored for three years (January 2006 through 

December 2008) by two U.S. Department of Energy national laboratories: the National 

Renewable Energy Laboratory (NREL) for the cold climate site in Aurora, Colorado, and Oak 

Ridge National Laboratory for the hot climate site in McKinney, Texas (Deru & MacDonald 

2007; MacDonald & Deru 2007). For comparison, a prototypical Walmart supercenter near each 

experimental store was monitored during the same period. The reference stores were nearly 

identical in size and function to the experimental stores, but contained the Walmart prototypical 
2

energy systems. This paper presents the major energy system experiments in HVAC, 

refrigeration, lighting, and renewable energy generation at the Colorado experimental store.

Figure 1. Aurora, Colorado, Experimental Store

Photo credit: NREL PIX 15780

Experiment Descriptions

The energy system experiments covered in this paper are briefly described and compared 

to the comparable systems in the reference store.

HVAC and Combined Heat and Power

The reference supercenter HVAC system consisted of three main air handling units 

(AHUs) that operate as 100% outdoor air systems and 37, 3- to 20-ton rooftop units (RTUs) to 

handle the loads not covered by the AHUs. The AHUs had carbon dioxide demand ventilation 

control, which never reached the set point of 900 ppm. The RTUs were cycled to meet the loads 

in the spaces they served and had minimum outside air settings and economizers for free cooling.

The main HVAC energy experiments are summarized in Table 1. The air distribution 

system in the experimental store consisted of 9 AHUs with indirect evaporative cooling and 28

RTUs. The AHUs delivered supply air through a large array of fabric ducts instead of through a 

small network of metal ducts in the reference store. The primary heating and cooling energy was 

delivered through hydronic loops for chilled water (CHW) and heating hot water (HHW). The 

HHW served heating coils in the AHUs and RTUs and the radiant floor loops. The CHW served 

the radiant floor loops and cooling coils in the AHUs and 13 of the RTUs. The other RTUs used 

standard direct expansion (DX) coils for cooling. The AHUs used economizers, indirect 

evaporative cooling, and CHW coils for cooling. Radiant floor heating and cooling loops were 

installed in the entryways, checkout area, around the open freezer cases, and in the garden and 

automotive centers. 

The HHW loop was served, in order of preference, by two, 415,000-Btu/h waste oil 

boilers, exhaust heat exchanger from the microturbines, and a 5.6 million-Btu/h gas boiler. The 

waste oil boilers burned used automotive oil from the automotive center and waste cooking oil 

from the kitchen. The kitchen oil system required heaters on the storage tank and piping system 
3 

to prevent the oil from solidifying. The CHW water loop was served by a 120-ton double-effect 

absorption chiller driven by heat reclaim from the microturbine exhaust. A transpired solar 

collector covered most of the south wall (back) of the store and preheated the ventilation air for 2 

of the AHUs and 11 of the RTUs near the back of the store.

Table 1. HVAC Experiments

System Experimental Store Reference Store

Radiant floor 

Radiant floor heating and cooling in the 

checkout area, entrances, frozen food aisles, 

garden center, auto center.

None 

Combined heat 

and power 

Six, 60-kW microturbines, a 1 0-ton doubleeffect absorption chiller, an air-to-water heat 

exchanger, and a cooling tower.

2 None

Indirect 

evaporative 

cooling 

Main sales floor was served by 9 AHUs with 

indirect evaporative cooling. The AHUs 

also have cooling coil supplied by chiller for 

hottest days.

All cooling was from packaged DX units.

Air distribution 

system

Main sales floor had fabric ducts to induce 

stratification in the store and reduce the

conditioned volume.

Air distribution from the AHUs and RTUs 

was through short metal ducts with diffusers 

near the ceiling.

Transpired solar 

collector air 

preheater

Two AHUs and 11RTUs along the south 

wall of the store received preheated air from 

the transpired solar collector in colder 

weather.

None

Recovered waste 

oil boilers

Burned used vehicle oil from auto shop and 

recovered cooking oil from the kitchen for 

HHW generation

All space heating was from gas fired furnace 

sections in the RTUs and unit heaters.

Refrigeration

The sizes of the refrigerated cases and walk-in coolers and freezers were very similar 

between the two stores; however, there were several experiments in the refrigeration systems

(see Table 2). The reference supercenter used a standard distributed case refrigeration system 

with four compressor racks and air-cooled condensers. All of the medium-temperature cases 

were open and all used linear fluorescent lighting. The experimental store incorporated an 

evaporatively cooled condenser, a glycol secondary loop for the medium-temperature system, 

doors on all medium-temperature dairy and deli cases, light-emitting diodes (LEDs) in all cases, 

enhanced evaporator coil surfaces, and high-efficiency electrically commutated fan motors. 

Table 2. Refrigeration Experiments

System Experimental Store Reference Store

Condenser evaporative condenser air-cooled condensers

Secondary loop

A heat exchanger and a secondary glycol 

loop were added to the medium-temperature 

refrigerant system. 

Refrigerant was distributed to the cases.

Refrigeration 

cases

Cases had high-efficiency, enhanced coil 

surfaces and electrically commutated highefficiency fan/motor packs in the mediumtemperature cases. Doors were added to 

dairy and deli cases.

Standard efficiency cases and no doors on 

medium-temperature cases.

Case lights All cases used LEDs T8 linear fluorescent lights
4

Lighting

The reference supercenter sales floor lighting layout used rows of two, 4-ft T-8 lamp 

fixtures 12 ft apart and skylights installed at a 3.9% skylight to floor area ratio (see Figure 2). 

The installed lighting power density (LPD) was 1.3 W/ft2

. The lights were dimmed to 20%, then 

turned off when natural light was adequate to meet the illuminance set point of 50 fc (500 lux). 

The experimental store lighting system experiments are listed in Table 3. The roof architecture 

of the experimental store incorporated three large sawtooth structures forming north-facing 

clerestory windows (see Figures 1 and 2). Skylights were included between these structures and 

in other areas of the store not served by the clerestory windows. The sales floor light fixtures 

used one, 5-ft high-output T-5 lamp. The lamps were dimmed to 20%, then turned off with 

available natural light. In both stores, the lights were controlled through the energy management 

system by one light sensor located in a skylight looking up at the sky. The control systems were 

calibrated to maintain the illuminance at approximately 50 fc (500 lux). The reference store 

sales floor was controlled as one large zone, and the experimental store was controlled as three 

zones because of the light and dark areas created by the sawtooth roof structure.

Figure 2. Daylighting in the Colorado Experimental (left) and Reference (right) Stores

Photo credit: Paul Norton/NREL Photo credit: Paul Norton/NREL 

Table 3. Lighting Experiments

System Experimental Store Reference Store

Sales floor 

lighting

5-ft T5HO lamps with 15 ft spacing between 

rows (installed LPD = 0.95 W/ft2)

T8 lamps with 12 ft spacing between rows 

(LPD = 1.3 W/ft2)

Sales floor 

daylighting

Three large sawtooth structures provide 

north-facing clerestory windows and space 

for photovoltaic panels

flat roof with 3.9% skylight to floor area 

ratio

Produce lighting

The height of the focused lighting over the 

produce was lowered and lower wattage 

metal halide bulbs 

Renewable Energy Systems

The reference store contains no renewable energy systems. The experimental store 

renewable energy experiments are listed in Table 4. Three photovoltaic (PV) systems are 

mounted on the sawtooth roof structures for total of 135 kW (Figure 3); a 50-kW wind turbine 

generator is located on a 120-ft pole next to the building. 
5

Table 4. Renewable Energy Experiments

Experiment Description

33-kW amorphous silicon PV 242, 136-W panels mounted on the rear sawtooth

50-kW single crystalline silicon PV 208, 250-W panels mounted on the front sawtooth

52-kW single and amorphous crystalline silicon PV 264, 190-W panels mounted on the rear sawtooth

50-kW wind turbine 50-kW wind turbine generator mounted on a 120-ft pole

Figure 3. Two of the PV Systems on the Aurora, Colorado, Experimental Store

Photo credit: Paul Norton/NREL

Monitoring

Extensive metering was installed in the experimental and reference stores to monitor the 

electricity end uses, HHW and CHW loops, gas and water use, and indoor and outdoor 

environmental conditions in accordance with the Procedure for Measuring and Reporting 

Commercial Building Energy Performance (Barley et al. 2005). These systems collected data 

from 234 points on 1-, 15-, and 60-minute frequencies on all major end uses, with more detailed 

data on the HVAC, refrigeration, and lighting systems. Several short-term (1–4 week) and 

seasonal monitoring activities focused on particular systems and data collected from the building 

energy management systems. The data acquisition systems were extremely reliable; very few 

data were missed between January 2006 and December 2008. 

Results

The highlights of the building and systems performance are covered in the following 

sections. Performance comparisons are generally between the experimental store and the 

reference store, but other comparison points are included as appropriate.

Whole Building

The annual energy performance for the experimental and reference stores is shown in 

Table 5. The story is very different depending on the metric used for comparison. The site 

energy use is 86% higher in the experimental store over the three years because a large amount 

of natural gas was used in the microturbines. The source energy use is very close, and both 
6

stores are slightly lower than the average of other Colorado supercenters during the same period. 

The CO2e emissions are 9% lower in the experimental store. The CO2e emissions from the 

electric utility grid are very high in Colorado because of the high use of coal and natural gas, 

which is why the experimental store can outperform the reference store for this metric.

Table 5. Whole-Building Performance

2006 2007 2008 Average

Site Energy (kBtu/ft2)

Reference 127 121 123 123

Experimental 218 228 238 228

Energy Savings –73% –89% –93% –85%

Source Energy (kBtu/ft2)

Reference 349 338 335 341

Experimental 339 347 348 345

Energy Savings 3% –3% –3% –1%

CO2e Emissions (metric ton) Total

Reference 5,871 5,690 5,626 17,186

Experimental 5,182 5,274 5,238 15,694

Emissions Savings 12% 7% 7% 9%

HVAC

The HVAC systems’ annual energy use is shown Table 6. The experimental store HVAC 

systems used almost twice as much electricity, 35% less gas, and 20% more total source energy 

than the reference store. This performance reflects the overall HVAC, envelope, and control 

system design.

Table 6. HVAC System Performance 

2006 2007 2008 Total

Electricity (MWh)

Reference 556 539 502 1,599

Experimental 1,136 1,084 921 3,141

Energy Savings –104% –101% –83% –97%

Gas (MWh)

Reference 2,433 2,351 2,598 7,382

Experimental 1,464 1,481 1,869 4,814

Energy Savings 40% 37% 28% 35%

Total Source Energy (MWh)

Reference 4,773 4,619 4,758 14,150

Experimental 5,837 5,662 5,493 16,993

Energy Savings –22% –23% –15% –20%

The HVAC electricity use in the experimental store was high because the fans, pumps, 

and air curtain heaters used a great deal of energy. The electricity use for the RTUs and AHUs 

was 33% higher in the experimental store than in the reference store because the AHU fans

operated continuously to keep the fabric ducts inflated. A control change after the first 18

months turned half the units off for six hours at night (deflating the fabric ducts), which reduced 

the load by 15 kW. The hydronic system pumps also required significant electricity. Design and 

control issues led to excessive pressure loss and run time on the pumps. Piping and control 

changes in the second year reduced pumping energy use by 43% from 2006 to 2008. The 
7

experimental store did not have double doors in the entry vestibules and used electric air curtain 

heaters to heat these spaces, which used 3% of the total store electricity in 2006. The reference 

store had two sets of doors in the vestibules and used gas unit heaters, which resulted in less than 

0.2% of the store total electricity being used for the air curtain heaters.

The waste oil boilers accounted for 3% and 4% of the total HHW load in 2006 and 2007, 

respectively. These systems were decommissioned in 2008 because of repeated maintenance 

issues and because the waste oil supply was too small to permit continuous burning throughout 

the heating season. The electricity used for heating the pipes and storage tank for the kitchen 

system equaled 93% of the energy generated from the system during the first two years of 

operation. 

The average measured delivered efficiency (delivered energy/incident energy) of the 

transpired solar collector was approximately 10% during the heating months with a peak value of

56%. The efficiency is mainly governed by the amount of air flow drawn through the collector. 

Several control problems and damper malfunctions led to the low average efficiency (Kozubal et 

al. 2008). The AHUs were controlled to cut off outside air flow when the outdoor air 

temperature dropped below 32°F to prevent the CHW coils from freezing; however, the 

delivered temperature from the transpired solar collector usually exceeded 32°F when the sun 

was incident on the collector. Thus, the AHUs drew air from the transpired solar collector 

during fewer than half of the available hours with favorable conditions over the 2007–2008 

heating season. 

Two of the AHU indirect evaporative cooling units, which account for 37% of the total 

AHU flow, were monitored closely in 2008. The wet bulb effectiveness was estimated to be 

47%; the ideal value for these units is 70%. The low effectiveness was mainly caused by the 

dirty inlet air filters and deposits on the surface of the heat exchanger surfaces. This was the 

third summer of use and the systems had not been maintained properly. Despite the lower than 

expected performance, these sections provided more than 50% of the cooling from these two 

units. 

The CHP system provided 52% of the experimental store’s electricity, 58% of the HHW 

load, and reduced monthly peak electricity power demand by an average of 200 kW over the 

three years. The electrical efficiency of the system was 24% and the total efficiency was 42% 

over the three year period. The system was controlled to produce the maximum amount of 

electricity all the time, and the thermal energy was often not fully utilized. 

Refrigeration

Several experiments were conducted in the experimental store’s refrigeration system, so

isolating any of them was difficult. The overall system performance was very successful,

showing 20% energy savings (see Table 7). Differences in store operation and volume of 

product sold are not known; however, the magnitude of these differences is expected to be much 

smaller than the overall energy savings. Most of the energy savings (29%) come from the lowtemperature (freezer) systems. The energy uses for each end use in the refrigeration systems are 

shown in Figure 4. Energy savings were achieved in every category except the defrost system in 

the low-temperature cases, most likely because of differences in the control strategies for the 

defrost and antisweat systems.
8

Table 7. Refrigeration Performance

Total Electricity (MWh) 2006 2007 2008 Total

Reference 1,550 1,416 1,397 4,363

Experimental 1,219 1,171 1,100 3,489

Total Energy Savings 21 % 17% 21% 20%

Low-temperature savings 34% 28% 24% 29%

Medium-temperature savings 10% 13% 19% 14%

Figure 4. Comparison of Refrigeration Energy Use by Component

Source: Author

The LED case lights and the compressors showed the largest absolute energy savings; the 

condenser showed the largest percent energy savings at 60%. The compressor energy savings 

arise from the reduced loads on the system, which mainly come from the evaporatively cooled 

condenser, the LED case lights, the antisweat heaters, and the evaporator fans. The energy 

savings from the addition of doors on medium-temperature cases seem to be approximately 

offset by the losses associated with the addition of the secondary loop, which adds pumps and a

heat exchanger. 

The LED case lights in the experimental store used 58% less energy than the linear 

fluorescent ones in the reference store during the first year. The LEDs were so successful that 

Walmart replaced the lights in the cases with doors in the reference store with motion sensorcontrolled LEDs in September 2007. The LEDs in the reference store reduced the energy use by 

45% and the motion sensors reduced the energy use by another 25% over the fluorescent lights. 

Walmart determined that LED case lights have a high enough return on investment that it

retrofitted most of the low-temperature cases in its U.S. stores with LEDs. 

The evaporatively cooled condenser reduces the saturated condensing temperature, which 

provides a more effective heat sink and reduces the load on the compressors. By studying the 

difference between summer and winter compressor performance, we can make some inferences 
9

about the impacts of the evaporatively cooled condenser. The compressor peak power demand 

for both stores was very similar in the winter, but the difference in the summer ranged from 20 

kW to 30 kW. The difference in monthly compressor energy use (reference store – experimental 

store) ranged from 4,000 kWh in the winter to 16,000 kWh in the summer. Both effects are 

primarily attributed to the evaporatively cooled condenser compared to the air-cooled condenser.

The addition of doors to multideck refrigerated cases is an important efficiency measure, 

but it was difficult to separate out the effect. Previous research has shown a 68% load reduction

and better product temperature control (Faramarzi et al. 2002). 

The main reason for using a secondary loop is to reduce the refrigerant charge. In fact, 

because of the losses in the heat exchanger and the added pumping energy for the glycol, the 

secondary loop likely increased the energy use in this store. Recent more compact and more 

efficient secondary loop designs show more than 90% reduction in refrigerant charge and are 

very close to being energy neutral compared to the distributed design.

Lighting

Table 8 shows the energy use for total interior, sales floor area, and perimeter lighting. 

The experimental store used about 7% less energy for total interior lighting but 38% more energy 

for lighting the sales floor area. This table also shows the lighting energy for the sales floor area 

assuming the ASHRAE Standard 90.1-2004 allowable LPD of 1.7 W/ft2 for a sales area and 24-

hour, 365-day operation (ASHRAE 2004). The experimental store used 65% less energy than 

would be allowed under Standard 90.1-2004.

Table 8. Lighting System Performance

2006 2007 2008 Total

Total Interior Lighting (MWh)

Reference 1,146 1,111 1,094 3,351

Experimental 1,048 1,057 997 3,103

Energy Savings 9% 5% 9% 7%

Sales Floor Lighting (MWh)

ASHRAE 90.1-2004 2,234 2,234 2,234 6,701

Reference 545 495 497 1,537

Experimental 708 728 685 2,121

Energy Savings Compared 

to the Reference Store –30% –47% –38% –38%

Energy Savings Compared 

to Standard 90.1-2004 65% 64% 65% 65%

Walmart has been experimenting with skylights and daylighting controls since its first 

demonstration store in Kansas in 1993; its prototypical design and control system is very 

efficient. Despite the experimental store’s 28% lower installed LPD for the sales floor, the 

typical nighttime peak power draw for the sales floor lighting for the same illuminance was 120 

kW in the experimental store and only 80 kW in the reference store. The experimental store’s 

very high ceilings from the sawtooth roof required a much higher LPD than the reference store’s 

uniform flat roof. During the day, however, the experimental store received more natural light

and could dim and turn off the lights for longer periods, because its daylighting aperture was 

20,129 ft2

; the reference store’s was only 5,780 ft2. The daylighting apertures for the two stores 

are very different and are compared on their overall function of providing natural light to the 

space. The experimental store roof construction provided more hours of adequate daylight and 
10

had lower summer heat gain, but it was more expensive and required more steel and glass, 

provided a less uniform distribution of daylight, and had a higher heat loss rate in cold weather.

Renewable Energy Systems

The energy production totals from the renewable energy systems are listed in Table 9. 

The thin-film silicon PV and the polycrystalline silicon PV systems were not operational until 

mid-June 2006; thus, their production during 2006 was much lower than during 2007 and 2008. 

All the PV systems experienced some downtime because of electrical and inverter faults. When 

the PV systems were operational, they performed within 5% of the design consultant’s expected 

performance. The second to last column in Table 9 lists the percent energy lost from the PV 

systems through the isolation transformers when the PV systems were not producing energy (at 

night, when the panels were covered with snow, etc.). During the winter, the monthly percent 

lost can reach 23% of the monthly total energy production. The inverter for the thin-film system

has an automatic disconnect built into the system and did not have the same problem of lost 

energy. The final column in Table 9 shows the net electricity produced (MWh) divided by the 

installed power (kW) for 2008. A value of 1.2 for this metric is considered to be good.

The wind turbine was an experimental system and had repeated problems that caused it to 

be out of operation more often than not. When the system was operational, it performed far 

below manufacturer’s expectations, which were based on inflated estimates of available wind 

resources. 

Table 9. Renewable Energy System Net Energy Production (MWh)

2006 2007 2008 Total % Lost

MWh/kW

Installed 

(2008)

33-kW thin film silicon PV 17.3 27.2 36.6 81.1 0.6% 1.14

50-kW single crystalline silicon PV 52.5 55.1 52.9 160.4 7.0% 1.12

52-kW polycrystalline silicon PV 31.4 61.3 64.1 156.7 6.1% 1.31

50-kW wind turbine 21.2 9.3 1.9 32.4

Total Renewable Energy 231.9 305.5 317.6 855.0

Conclusions

Walmart has a long history of pushing the envelope in building and operating energyefficient buildings. The 2005 experimental stores constructed in Texas and Colorado are two 

examples of this effort. Valuable lessons were learned from monitoring the experimental and 

reference stores about what works well according to Walmart standard practices. Highlights of 

the lessons learned from the Colorado store include:

• Evaporative cooling can work well in the dry Colorado climate. It provided 

approximately 50% of the space cooling for the AHUs. The refrigeration system 

evaporatively cooled condenser provided summertime peak power reductions of 30 

kW and energy savings of 16,000 kWh/month. 

• For large single-story buildings, the energy performance of electricity- and natural 

gas-powered distributed systems is difficult to beat. Hydronic-based systems need 

multiple energy recovery opportunities and close evaluations of the pumping and 

control design if they are to be effective.
11

• The transpired solar collector effectively delivered preheated ventilation air, but it 

must be controlled properly to optimize performance.

• Combined heat and power systems must have consistent thermal and electrical loads. 

This store did not have a consistent thermal load and was costly to operate.

• Secondary refrigeration loops significantly reduce refrigerant charge and can provide 

at least equal energy performance to standard refrigeration systems.

• LED case lights can provide significant energy savings (about 50%) over linear 

fluorescent lighting.

• T5HO lamps in this application did not show energy savings over properly controlled 

T8 lamps.

• North-facing clerestories did not deliver more energy savings than the standard 

skylights already used by Walmart. 

• Control sequences should be simple and robust so operators can easily understand 

how they work and interact with other system controls.

• Renewable energy systems should be monitored continuously so problems can be 

corrected in a timely fashion.

• Renewable energy systems should be designed to eliminate or minimize parasitic 

power draws.

Walmart is continually improving the design and operation of its buildings. Its latest 

efforts for high-efficiency buildings combine lessons from these experimental stores and applied 

them with lessons from other projects in integrated and climate-sensitive designs. The Aurora,

Colorado, experimental store has been retrofitted to remove some of the failed experiments and 

improve on the operation of other systems based on the lessons learned. The store will be 

monitored for one more year with the new configurations and compared to the first three years of 

operation.

References

ASHRAE. 2004. Energy Standard for Buildings Except Low-Rise Residential Buildings. 

ANSI/ASHRAE/ IESNA Standard 90.1–2004. Atlanta, Ga: American Society of Heating, 

Refrigerating and Air-Conditioning Engineers.

Barley, C.D., M. Deru, S. Pless, P. Torcellini, and S. Hayter. 2005. Procedure for Measuring 

and Reporting Commercial Building Energy Performance. Golden, Colo: National 

Renewable Energy Laboratory.

Deru, M., and M. MacDonald. 2007. “Wal-Mart Experience: Part Two.” ASHRAE Journal Vol. 

49(10), 22-27.

Faramarzi, R.T., B.A. Coburn, and R. Sarhadian. 2002. “Performance and Energy Impact of 

Installing Glass Doors on an Open Vertical Deli/Dairy Display Case.” ASHRAE AC-02-7-2, 

ASHRAE 2002 Winter Meeting.

Kozubal, E., M. Deru, S. Slayzak, P. Norton, G. Barker, and J. McClendon. 2008. “Evaluating 

the Performance and Economics of Transpired Solar Collectors for Commercial 

Applications. Pacific Grove, Calif.: 2008 ACEEE Summer Studies. 

MacDonald, M., and M. Deru. 2007. “Wal-Mart Experience: Part One.” ASHRAE Journal Vol. 

49(9).
F1147-E(10/2008)

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REPORT NUMBER

NREL/CP-550-48295

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)

NREL

11. SPONSORING/MONITORING

AGENCY REPORT NUMBER

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)

Walmart opened two experimental stores—one in Colorado and one in Texas—in 2005 to serve as test beds for 

several advanced building systems. Each embodied more than 50 experiments covering materials, water systems, 

energy systems, and renewable energy production. Walmart worked for three years with the National Renewable 

Energy Laboratory for the Colorado Store and Oak Ridge National Laboratory for the Texas store to monitor, 

analyze, and report on their performance. HVAC experiments included waste oil boilers, a microturbine/absorption 

chiller combined heat and power system, evaporative cooling, and a transpired solar collector. The refrigeration 

systems integrated a medium-temperature secondary loop, evaporatively cooled condenser, doors on mediumtemperature cases, and light-emitting diodes on cases. Experiments in the lighting systems included a redesigned 

roof for clerestory daylighting and T-5 fluorescent lamps. Three photovoltaic systems for a total of 135 kW and a 50-

kW wind turbine are also included. The energy system performance was compared to the measured performance of 

a prototypical Walmart store and to other benchmarks. 

15. SUBJECT TERMS

walmart; experimental store; test bed; advanced building

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT

UL

18. NUMBER 

OF PAGES

19a. NAME OF RESPONSIBLE PERSON

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18