Technical Support Document: Development of the Advanced Energy Design Guide for Medium Box Retail -- 50% Energy Savings

Abstract

A number of colleagues made this work possible. The authors greatly appreciate the assistance of Brent Griffith and the NREL EnergyPlus analysis and modeling team. Their simulation development and support allowed us to evaluate a variety of energy efficiency technologies. We would also like to thank NREL's High Performance Computing Center's Wesley Jones and Jim Albin for their support in providing dedicated Linux cluster nodes for the simulations needed for the analysis. Finally, we extend our thanks to those who helped edit and review the document: Stefanie Woodward, Michael Deru, and Ian Doebber (all of NREL). iv Executive SummaryThis report documents technical analysis aimed at providing design guidance that achieves wholebuilding energy savings of at least 50% over ASHRAE Standard 90.1-2004 in medium-sized retail buildings. It represents an initial step towards determining how to provide design guidance for energy savings targets larger than 30%, and was developed by the Commercial Buildings Section at the National Renewable Energy Laboratory (NREL), under the direction of the DOE Building Technologies Program.This report:• Documents the modeling and integrated analysis methods used to identify cost-effective sets of recommendations for different locations and business activities.• Demonstrates sets of recommendations that meet, or exceed, the 50% goal. There are forty eight sets of recommendations, one for each combination of sixteen climate zones and three levels of unregulated plug loads.This technical support document (TSD), along with a sister document for grocery stores (Hale et al. 2008), also evaluates the possibility of compiling a 50% Advanced Energy Design Guide (AEDG) in the tradition of the 30% AEDGs available through the American Society of Heating, Refrigerating, and AirConditioning Engineers (ASHRAE) and developed by an inter-organizational committee structure. In particular, we comment on how design guidance should be developed and presented in the next round of 50% TSDs for deployment as AEDGs. MethodologyBecause it is important to account for energy interactions between building subsystems, NREL used EnergyPlus to model the predicted energy performance of baseline buildings and low-energy buildings to verify that the goal of 50% energy savings can be met. EnergyPlus was selected because it computes building energy use based on the interaction of the climate, building form and fabric, internal gains, HVAC systems, and renewable energy systems. Percent energy savings are based on a minimally codecompliant building as described in Appendix G of ASHRAE 90.1-2004, and whole-building, net site energy use intensity (EUI): the amount of energy a building uses for both regulated and unregulated loads, minus any renewable energy generated within its footprint, normalized by building area.The following steps were used to determine 50% savings:• Define architectural-program characteristics (design aspects not addressed by ASHRAE 90.1-2004) for typical retail stores, thereby defining prototype models....

General Merchandise 50% Energy Savings Technical Support Document

“…We attempted to model indirect evaporative cooling in the RTUs, but were unsatisfied with the modeling results. We could not dynamically model the effects of bypassing the indirect evaporative cooler when it was not needed, so we are uncertain of our previous finding (Hale et al 2008b) that evaporative cooling should not be used in any climate zone. The EnergyPlus modeling methods and the input data need to be refined.…”

“…The lower bound originates from the inclusion of stores up to 20,000 ft 2 (1,860 m 2 ) in the Advanced Energy Design Guide for Small Retail Buildings (ASHRAE et al 2006). The upper bound encompasses so-called medium box and some big box stores according to the definitions in Hale et al (2008b). Our main prototype store has a floor area of 40,500 ft 2 , and is thus a medium box store.…”

“…(This floor area actually represents the boundary between medium box and big box defined in Hale et al (2008b).) The big box store model development and results are discussed in Section 4.3.…”

“…Unlike earlier work (Hale et al 2008b), this TSD enforces a humidity set point using humidistats and reheat coils fed by DX condenser waste heat (superheat). The next step is to explore advanced dehumidification strategies such as desiccant-based humidity control.…”

“…It builds on previous 2 work (Hale et al 2008a;Hale et al 2008b) that established a basic methodology for finding building designs that achieve 50% energy savings over ASHRAE 90.1-2004. These analyses improve on the earlier work in that (1) the analysis assumptions were reviewed by external experts; (2) an extended methodology for determining alternative 50% designs was developed; and (3) the extended methodology was applied to select climate zones.…”