The search for refrigerants that perfectly balance environmental, economic and safety concerns is continuing. Unfortunately, this quest throws customers and end-users off balance. Planning is stressful when the future is subject to change. Fortunately, in recent years, technology has developed to the point that it is possible to build a long-lasting platform for low-GWP commercial refrigeration.
Proven technologies are now available in four areas:
1. Developments in CO2 refrigeration
Until recently, it’s been impossible to apply the energy efficiency, safety and environmental benefits of transcritical CO₂ systems in all climates. Following years of engineering and field testing, the Danfoss Multi Ejector Solution™ was developed, which along with AK-PC 782A rack controller technology, enables a CO2 refrigeration system to operate in a transcritical zone, even in warm climates. The result is up to 10% annualized savings compared to prior transcritical parallel compression systems and up to 30% energy savings during the hottest hours of the year compared to booster systems. Moreover, compressor discharge temperatures in transcritical operation can exceed 250°F. This heat, which is usually rejected by a gas cooler, can be reclaimed by heat exchangers mounted before the gas cooler. This combination of technologies brings all the safety, economic and environmental benefits of CO2 to many large and mid-size U.S. commercial refrigeration applications, regardless of location.
2. Developments in Demand Response
The high usage of electricity by supermarkets can make it very advantageous to participate in demand response programs. As the name implies, in a demand response program, the utility sends a signal to a central control unit that utilizes the flexibility of the application to reduce power to motors, compressors and other electrical equipment. The signal triggers a reduction in electric consumption for brief periods ranging from less than one minute to long periods within a 24-hour interval, depending on the application.
Not every utility offers demand response programs. The utilities offering these programs pass on the prospective savings to participants. Economic benefits are based on the customer’s commitment to respond. A carefully designed demand response program using appropriate refrigeration control and management systems can achieve substantial energy savings while protecting food integrity.
For example, the Danfoss ADAP-KOOL® System Manager AK-SM 800 Series not only features a full web interface for remote monitoring and data management—it also incorporates built-in demand response capabilities that can take advantage of utility incentive programs. Additionally, it supports heat-reclaim technology and a variety of refrigerants, including CO2.
Store owners and energy managers should consult with utilities to evaluate their flexibility to shift the demand and the time of electric consumption.
3. Developments in thermal storage and related thermal-shifting technologies
Thermal storage makes it possible to shift electricity consumption from expensive peak rates during the day to lower rate periods during the night. Thermal storage tanks hold a liquid medium chilled at night for cooling display cases, reducing equipment run time.
In a supermarket application, the display cases can themselves function as a form of thermal storage. Lowering display-case temperatures during off-peak hours enables compressors to run less during peak hours. Thermal storage capacity can be used to produce a revenue stream when it’s connected to other stores through a district heating and cooling (DHC) system. Heat recovery technology can also be used to capture heat otherwise rejected by the refrigeration system’s condensers. For stores using CO2 with a heat-reclaim system, the size of a separate heat source—such as a boiler—can be greatly reduced or even eliminated.
4. Developments in the decarbonized grid
Called “the largest machine ever built,” the more than century-old electric grid is the largest producer of greenhouse gases. Fortunately, technology exists today to re-engineer that machine to cut CO2 emissions dramatically. Increased use of renewable power (wind and solar), continued use of stable nuclear power and use of responsive hydropower are low-carbon resources that are gradually creating a decarbonized electricity supply. Models of a moderately decarbonized electricity system for the year 2050 estimate CO2 emissions intensity could be 60% to 80% lower than today’s U.S. grid.
In the U.S., over 21 million kWh of electricity in 2017 was used in process cooling and refrigeration for food. By using low-GWP refrigerants, demand response and thermal storage technologies compatible with an increasingly decarbonized grid, air conditioning can help shrink its share of greenhouse gas emissions.
These recent technological developments are supporting the transition to low-GWP refrigerants. While policies may fluctuate, research and innovation are bringing proven products and platforms to market that can be implemented today in more food and commercial refrigeration applications than ever before. Advances in transcritical CO2 systems are also providing an attractive value proposition for many supermarkets. Other developments—demand response, thermal storage and heat reclaim—complement the trend toward a decarbonized electric grid and significantly reduce commercial refrigeration’s carbon footprint. Utilities and regulators play a vital role in creating an HFC-free future. Incentives and policies can reassure supermarket owners operating on tight margins that their investment will pay off by boosting profits in the short term, as well as the environment in the long run.