Refrigeration Playbook: Natural Refrigerants Selecting and Designing Energy- Efficient Commercial Refrigeration Systems That Use Low Global Warming Potential Refrigerants Caleb Nelson, Chuck Reis, Eric Nelson, James Armer, Rob Arthur, Richard Heath, and James Rono CTA Architects Engineers Boise, Idaho Adam Hirsch and Ian Doebber National Renewable Energy Laboratory Golden, Colorado NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Technical Report NREL/TP-5500-63821 March 2015 Contract No. DE-AC36-08GO28308 Refrigeration Playbook: Natural Refrigerants Selecting and Designing Energy- Efficient Commercial Refrigeration Systems That Use Low Global Warming Potential Refrigerants Caleb Nelson, Chuck Reis, Eric Nelson, James Armer, Rob Arthur, Richard Heath, and James Rono CTA Architects Engineers Boise, Idaho Adam Hirsch and Ian Doebber National Renewable Energy Laboratory Golden, Colorado Prepared under Task No. ARCB1102 Prepared under Subcontract No. AGG-4-42181-01 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. National Renewable Energy Laboratory Technical Report 15013 Denver West Parkway NREL/TP-5500-63821 Golden, CO 80401 March 2015 303-275-3000 • www.nrel.gov Contract No. DE-AC36-08GO28308 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. 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The authors would like to thank Arah Schuur and Glenn Schatz of the U.S. Department of Energy Building Technology Office for their support and guidance on this work. The authors would also like to acknowledge the contributions of peer reviewers from industry and at NREL who provided feedback to improve this report, including Neil Monson, Target Corporation; Dustin Searcy, Parker Hannefin Corporation; Shitong Zha, Hill Phoenix; Ren Anderson, Eigen Energy; and Ron Judkoff, NREL. iv This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Abbreviations and Acronyms ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers ASTM American Society for Testing and Materials ANSI American National Standards Institute Btu British thermal unit CBP Commercial Building Partnerships CFC chlorofluorocarbons CFM cubic feet per minute CO2 carbon dioxide DOE U.S. Department of Energy DX direct expansion EPA U.S. Environmental Protection Agency EEV electronic expansion valve EUI energy use intensity GHG greenhouse gas GWP global warming potential HCFC hydrochlorofluorocarbon HFC hydrofluorocarbon HFO hydrofluoroolefin HVAC heating, ventilation, and air-conditioning LT low temperature MT medium temperature NH3 ammonia NREL National Renewable Energy Laboratory PRV pressure relief valve psi pounds per square inch TEWI Total Equivalent Warming Impact W Watts v This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Executive Summary Background This refrigeration playbook provides guidance to refrigeration system design teams about selecting energy-efficient refrigeration systems that use low-global warming potential (GWP) refrigerants. It emerged from work done as part of the U.S. Department of Energy’s Commercial Building Partnerships (CBP). CBP was a public/private, cost-shared initiative that demonstrated cost-effective, replicable ways to achieve dramatic energy savings in commercial buildings. CBP aimed to reduce energy use by 50% in new construction and 30% in existing buildings compared with minimum code requirements or pre-retrofit energy use. Building owners teamed with the U.S. Department of Energy, national laboratory staff, and private sector experts to explore and implement energy-saving ideas and strategies. Although the analysis presented here was distilled from design work done for a CBP pilot project with the Defense Commissary Agency (which completed construction after CBP had finished), the guidance and tools are intended to benefit the entire supermarket industry. In recent years, supermarket refrigeration systems have been trending toward using smaller refrigerant charges and applying synthetic refrigerants with lower GWP or natural refrigerants with negligible GWP. In many instances, the driving factors for alternative refrigeration system decisions are marketing exposure and demonstrating good environmental stewardship. Because low-GWP and natural refrigerants have favorable thermodynamic properties compared to stand- ard synthetic refrigerants, energy-efficient systems that also have low-GWP can be designed. Purpose The purposes of this playbook and accompanying spreadsheet are to generalize the detailed CBP analysis and to put tools in the hands of experienced refrigeration designers to evaluate the performance of multiple alternative refrigeration system designs for different climates across the United States. It is also intended to alert designers to the safety and compliance considerations that must be taken into account when working with alternative refrigerants. Scope This playbook was written for supermarket design teams at companies considering low-GWP or natural refrigeration systems. Although the concepts discussed apply to a variety of refrigeration technologies, when considering other applications such as convenience stores or industrial refrigeration, care should be taken to determine which parameters should be adjusted to match the application. The calculations presented in the accompanying spreadsheet and described in the appendices will help users estimate energy savings and environmental impacts; they do not necessarily reflect the actual savings realized by a specific system and building. Variables such as low-side system configuration, building usage patterns, and weather patterns can significantly impact the performance of the refrigeration system. Brief chapter summaries follow. • Chapter 1 presents the goals and scope of the playbook in detail and describes the approach to energy analysis. • Chapter 2 covers recent history, describes the trends that have focused attention on low- GWP refrigeration systems, and introduces a metric that encompasses the direct environmental impact of refrigerant emissions and indirect effects through the energy vi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. generation required to power the system called the Total Equivalent Warming Impact (TEWI). • Chapter 3 presents the six alternative refrigeration system configurations considered in the report. System diagrams accompany each application. They are: o Low-temperature (LT) or medium-temperature (MT) carbon dioxide (CO2) overfeed o MT hydrofluorocarbon direct expansion (DX) with LT CO2 DX cascade o Hydrofluorocarbon DX primary over combined MT overfeed with LT CO2 DX o Ammonia (NH3)-flooded primary over combined MT overfeed with LT CO2 DX o CO2 transcritical booster system o Self-contained water-cooled hydrocarbon. • Chapter 4 describes the physical properties of NH3, CO2, and propane and their implications