Radiative Sky Cooling-Enabled Efficiency Improvements on Commercial Cooling Systems

Global warming has already resulted in greater cooling system energy loads and more days per year with a demand for cooling. Peak summer temperatures are often 3 to 5 degrees Fahrenheit warmer than they were 10 years ago. As ambient temperatures continue to rise, refrigeration and air conditioning systems will become less efficient, and the demand for cooling will increase as more people install and run air conditioning to stay cool. SkyCool Systems has pioneered a passive cooling panel that uses multilayer reflective optical film to cool fluids with zero input electricity and without evaporating water. The panels can be connected to any air conditioning or refrigeration system to improve efficiency and cooling capacity. SkyCool Systems installed its energy-saving, capacity-improving panel arrays at two California supermarkets.

At the first site, located in Red Bluff, California, SkyCool Systems installed an 80-panel array to precool the supermarket’s refrigeration system. The array added 30 to 45 kilowatts of additional heat rejection to the site’s air-cooled condenser and resulted in 50 pounds per square inch lower compressor discharge pressures. This yielded a maximum energy savings of 15 percent and lowered the peak demand for the refrigeration system by 5 to 7 kilowatts. Additionally, the site’s rooftop condenser needed to be cooled with water from a sprinkler to increase its capacity in the summer. With the addition of the array, the site was able to remove the sprinkler from the roof, saving tens of thousands of gallons of water each year.

At the second site, located in Milpitas, California, SkyCool Systems installed a 60-panel array that subcooled the refrigeration system when the ambient air temperature was lower than 75 degrees Fahrenheit and precooled the condenser the rest of the year. When the subcooler was operating, SkyCool Systems was able to add 10 to 25 degrees Fahrenheit of additional subcooling, resulting in a 15- to 20-percent reduction in energy usage. When the precooler was running, the array was able to add 25 to 30 kilowatts of additional capacity to the condenser, lowering the power demand in the summer by 3 kilowatts. The array resulted in nearly 20,000 kilowatt-hours of energy saved.