A recast of a presentation done for the Fairfax Chapter of Association of Energy Engineers in November of 2013. Presentation focuses on the the Advanced Energy Design Guides published by ASHRAE with association of AIA, USGBC, and IES with funding and technical support from DOE, NREL, and PNNL. In addition, the DOE Advanced Retrofit Guides are also discussed. Both sets of guides are available for download from this resource database.
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In 2011, the U.S. Department of Energy’s Building Technology Office (DOE’s BTO), with help from the Better Buildings Alliance (BBA) members, developed a specification (RTU Challenge) for high performance rooftop air-conditioning units with capacity ranges between 10 and 20 tons (DOE 2013). In April 2013, Carrier’s 10-ton WeatherExpert unit model was recognized by DOE to have met the RTU Challenge specifications. Carrier also committed to have its entire line of WeatherExpert models for commercial buildings compliant with integrated energy efficiency ratio (IEER) meeting the RTU Challenge requirement. This report documents the development of part-load performance curves and their use with the EnergyPlus simulation tool to estimate the potential savings from the use of WeatherExpert units compared to other standard options.
A detailed EnergyPlus model was developed for a prototypical big-box retail store. The model used the performance curves from the new model along with detailed energy management control code to estimate the energy consumption of the prototypical big-box retail store in three locations. The energy consumption by the big-box store was then compared to a store that used three different reference units. The first reference unit (Reference 1) represents existing rooftop units (RTUs) in the field, so it can be considered the baseline to estimate potential energy savings from other RTU replacement options. The second reference unit (Reference 2) represents RTUs in the market that just meet the current (2015) Federal regulations for commercial equipment standards, so it can be used as the baseline to estimate the potential for energy savings from WeatherExpert units in comparison with new RTUs that meet the minimum efficiency requirements. The third reference unit (Reference 3) represents units that meet ASHRAE 90.1-2010 requirements. For RTUs with cooling capacity greater than 11,000 Btu/h, ASHRAE 90.1-2010 (ASHRAE 2010) requires two-speed fan control or variable-speed fan control.
The following conclusion can be drawn about the comparison of energy cost for WeatherExpert unit compared to the three reference units:
• Using Reference 1 as the baseline, WeatherExpert units result in about 45% lower heating, ventilation and air conditioning (HVAC) energy cost in Houston, 55% lower cost in Los Angeles, and 35% lower cost in Chicago. The percentage savings of electricity cost is more than 50% for all three locations.
• Using Reference 2 as the baseline, WeatherExpert units result in about 39% lower HVAC energy cost in Houston, 52% lower cost in Los Angeles, and 32% lower cost in Chicago. The percentage savings of electricity cost is 44%, 55%, and 57%, respectively for the three locations.
• Using Reference 3 as the baseline, WeatherExpert units result in about 25% lower HVAC energy cost in Houston, 35% lower cost in Los Angeles, and 18% lower cost in Chicago. The percentage savings of electricity cost is 29%, 38%, and 37%, respectively.
Based on the simulation results, the WeatherExpert RTU Challenge unit, if widely adopted, could lead to significant energy, cost and emission reductions. Because the cost of these units was not available and because the costs would be specific to a given installation, no attempt was made to estimate the potential payback periods associated with any of the three reference scenarios. However, if the incremental cost relative to any of the three reference cases is known, one can easily estimate a simple payback period.
NREL contracted with the Energy Center of Wisconsin to review the Commercial Building Partnerships projects and identify and compile the best practices for ten energy conservation measures that were tested in those projects. The resulting compilation is presented in this report.
The following guide is intended to provide you with an understanding of the value of submetering on a campus and how to set-up and maintain a submetering program. Case studies from four prominent schools are included to illustrate different solutions for campus submetering. To learn more about reducing energy and water consumption on campuses through benchmarking, upgrades and behavior change, review the companion document "Campus Benchmarking Guide."
Southface developed this Campus Benchmarking Guide to help colleges and universities assess the energy and water usage of both small and large buildings and compare them to ENERGY STAR’s index of average energy usage for over 80 relevant building types. This enables the buildings with the greatest opportunities for savings to be easily identified regardless of size.
The Fire Station Efficiency Solutions Package aims to assist municipalities nationwide to reduce carbon footprints, lower utility bills, and increase resiliency by selecting improvements that will reduce energy and water use in existing buildings by at least 20%. This toolkit is a product of a collaboration between the City of Atlanta and Southface Energy Institute. Through this solutions package, municipalities and fire departments will be equipped to plan and implement individual and portfolio-level upgrades.
The Recreation Center Efficiency Solutions Package aims to support municipalities nationwide with selecting efficiency improvements to reduce energy and water use at existing recreation centers by at least 20%. This toolkit is a product of a collaboration between the City of Atlanta and Southface Energy Institute. This package intends to inform local municipalities on how to approach conserving energy and water, and implementing institutional efficiency policies across a portfolio of recreation centers.
Case study on how Fontana Unified School District in southern California used grant money to install 201 high-efficiency Carrier rooftop units (RTUs) in 30 buildings across four schools, resulting in $214,000 saved per year.
Case study on how Arby's Restaurant Group's innovative approach to rooftop unit (RTU) management garnered them $287,000 and 2.9 million kWh in annual savings.
Article in the Whole Building Design Guide about the uses and features of metal roofs that meet "cool roof" standards.