Refrigeration is a massive energy consumer in commercial and industrial buildings. In the commercial sector alone, it consumes around 17 percent of all electricity.1 Rising demand and a warming climate mean almost certain expansion for refrigeration. This also means tremendous opportunity for energy savings; effort has gone into implementing many measures to reduce energy use in refrigeration across the country. But there is still a long way to go. Our research team has continued to look for more aggressive solutions in the refrigeration world and test them in real applications. Together, these new measures could improve performance significantly even in already well-operating supermarkets, restaurants, reduce the climate impact of refrigeration by using alternative refrigerants and less energy.
Use of VFDs in refrigeration
Variable frequency drives (VFDs) provide the ability to regulate frequency, fan speed and therefore the power delivered to motors in many HVAC applications. They are also a good option in refrigeration, specifically for condenser fans. Most existing refrigeration condensers in the U.S. have fixed-speed fans, so VFDs represent an important opportunity. Our field research shows that adding VFDs can save 1,400-1,500 kWh/horsepower which represents about 50 percent savings.
Q-Sync motors are a new type of innovative, highly efficient and cost-effective, permanent magnet synchronous (PMSM) motor. Between our own field research and the existing literature, studies find that in reach-in and walk-in cooler and freezers, Q-Sync motors cost-effectively use 50% - 80% less energy than traditional shaded-pole (SP) and permanent split capacitor (PSC) motors, and are even more efficient than the newer electronically commutated (EC) motors.
Innovations are on the horizon—such as the shift to alternative refrigerants—that may transform every element of the refrigeration system. Recent climate change strategies have shown that the refrigerant itself has as much climate impact as the energy going into the system.2 This is because the ability of incumbent refrigerants to trap heat inside the atmosphere can be orders of magnitude more potent that carbon dioxide. That is why carbon dioxide as a refrigerant could have enormous climate benefits and has already made significant strides in some major store chains in the Midwest. Other alternative refrigerants are now being tested in more progressive markets. This could lead to some changes in the continued trend toward more energy efficient refrigeration equipment, as some refrigerants with lower direct global warming potential lead to greater energy use. We are examining these options for some of our clients in the Midwest, including limited initial field data collection. Stay tuned for more from us on this topic.
There are still more innovations coming that we hope to investigate. For example, commissioning has been shifting to monitoring and data-based approaches in many high-performance buildings. A few pioneering firms are beginning to apply this principle to supermarkets, where controls have a bigger per-unit impact. Anecdotal evidence shows success. We are also exploring the impact of putting doors on refrigerated cases, which has been a known measure for some time but for which the economics are misunderstood, due to concerns over impact on food sales.
1The Role of Refrigeration in the Global Economy. International Institute of Refrigeration. November 2015.
2Hawken, P. Drawdown. Penguin, 2017.