Technologies using refrigerants with a Global Warming Potential (GWP) less than 150 are considered the best-in-class, or ‘climate- friendly’ technologies for new retail refrigeration systems and equipment. Refrigerants like carbon dioxide (R-744), hydrocarbons such as propane (R-290) and isobutene (R-600a), and ammonia (R-717) all have GWPs less than 10. If U.S. supermarkets voluntarily adopt technologies using only low-GWP refrigerants in all new stores beginning in 2020, they can cumulatively avoid emissions of 20.8 million MTCO2e by 2025. Examples of such technologies include:
Transcritical CO2 systems
Cascade or indirect systems using a combination of two low-GWP refrigerants
Micro-distributed systems using hydrocarbon condensing units on a chilled water or glycol loop
Stand-alone display cases using hydrocarbons
Conversions to Lower-GWP
Companies can achieve additional emission reductions by converting all or part of an existing refrigeration system to use low or medium-GWP refrigerants. Through performing gas conversions or retrofits on existing systems using high-GWP HFCs like R-404A, supermarkets can significantly reduce the average GWP across all stores. In some cases, a secondary loop on the low side of a system can be converted to use a very low-GWP refrigerant like CO2, while still using some HFCs on the high side but significantly reducing the HFCs in that store. In some cases it may be appropriate to replace part of all of the HFC refrigerant with a medium GWP blend. These blends can reduce GWPs by up to 70% compared with R-404A, while requiring little or no changes to system components. However, these blends still contain some HFCs and have a considerable climate impact of up to 1400, so are not considered climate friendly over the long term or in new equipment and systems. Strategies that incorporate conversions of existing systems to reduce average GWP of refrigerants across all U.S. supermarkets by 50% in 2025, could reduce U.S. emissions by 22.7 million metric tons CO2e annually.
Increasing Energy Efficiency
There is a tremendous opportunity for leading companies to pair adoption of low-GWP refrigerants with other technologies to enhance the overall efficiency of refrigeration systems. In many cases low-GWP refrigerants are also more energy efficient than HFCs and can contribute to energy savings and reductions in total cost of ownership. Hydrocarbons and ammonia are extremely efficient refrigerants in all temperature conditions. Carbon dioxide is very energy efficient in temperate climates and can be used efficiently in warm or tropical regions either as a secondary refrigerant or when paired with energy enhancing technologies. Complimentary energy enhancing technologies and design choices include parallel compression, adiabatic coolers, liquid/gas ejectors, heat reclaim, and design improvements like LED lights and installing doors and night shades on open display cases. Adoption of low-GWP refrigerant technologies should be a key component of a company’s overall strategy to decrease energy use and minimize the total warming impact of cooling. For more information and case studies read EIA’s report on energy efficiency in HFC-free supermarket refrigeration.