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Technology Adoption

 
 

Climate-Friendly Technologies 

 

Technologies using refrigerants with a Global Warming Potential (GWP) of less than 10 are considered ultra-low, or 'climate-friendly' technologies for new stores and remodels. 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 adopt technologies using only ultra-low GWP refrigerants in all new stores beginning in 2025, they can cumulatively avoid emissions of 45.7 million MTCO2e by 2030. Examples of such technologies include:

 
 

Conversions of Existing HFC Systems

 
Companies can also achieve emission reductions by converting all or part of an existing HFC refrigeration system to use low-GWP refrigerants. In some cases, a secondary loop on the low side of a system can be converted to a hybrid system that uses 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. However, these HFC blends still carry a considerable climate impact of up to a 1400 GWP, 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% by 2030, could reduce U.S. emissions by 33.7 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.

Types of Low-GWP Supermarket Refrigeration Systems

Transcritical CO2 systems

A type of HFC-free central refrigeration system using only carbon dioxide (R744) with a GWP of 1 as a refrigerant. In higher ambient climates where temperatures frequently exceed the critical point of CO2, 88°F, these systems operate in a ‘transcritical’ mode which can benefit from the use of energy-efficiency enhancing features such as adiabatic cooling, parallel compression, and ejector technologies in order to maintain high energy performance and reduce electricity consumption.

Cascade or indirect systems

These systems often use two or more low-GWP refrigerants, comprised of a primary and secondary refrigerant. The primary refrigerant, typically in a chiller on the roof or in a machine room, is used to cool a secondary refrigerant, usually CO2, which circulates through the display cases. Usually either ammonia (R717) with a GWP of 0, propane (R290) with a GWP of 3, or another hydrocarbon is used as the primary refrigerant.

Distributed and Micro-distributed systems

In a distributed system, the centralized refrigeration system is replaced by smaller refrigeration units located near the refrigerated cases they serve. This system can also be designed using a chilled water or glycol loop that is used as a heat transfer fluid to carry heat away from the distributed systems, increasing efficiency. In some cases a distributed or micro-distributed system may provide advantages in terms of flexible layout or changes in configuration of equipment, as well as easier repair to a single case or set of cases without having to shutdown the entire refrigeration system.

Stand-alone display cases using natural refrigerants

One to three door refrigerated or freezer cases that can be designed using either a hydrocarbon refrigerant such as propane (R290) or CO2 (R744), with GWPs of 3 or 1 respectively. Typically, this type of equipment is self-contained with all parts of the refrigeration system contained within the equipment itself with no assembly or installation required often referred to as “plug and play solutions”. With ongoing changes to safety standards, increasing safe use of energy efficient hydrocarbons is expected in these pieces of equipment. In some cases, stand-alone or self-contained equipment can replace part or all of a centralized refrigeration systems depending on store needs.

Hybrid HFC/Low-GWP Systems (Conversion of an existing system only)

Similar to a cascade or indirect system above, this type of system uses two or more refrigerants in a primary/secondary loop system. In this case, a system using HFCs may have one of the secondary refrigerants converted to a low-GWP refrigerant such as CO2 (R744). Often CO2 is used as the secondary refrigerant for a series of low-temperature or freezer cases.