September 25, 2008

Solar-Powered Adsorption Cooling

Solar-powered cooling is an attractive concept in that one utilizes solar energy, which is the largest component of a building’s cooling load, to drive a heat-activated air-conditioning system, thus reducing or eliminating the need for conventional, electric-powered air conditioning. Most solar-powered air-conditioning systems to date have been based on well-known absorption refrigeration, which requires difficult-to-handle fluids like ammonia or aqueous lithium bromide, and complicated system components. We are instead researching an alternative refrigeration system, based on the adsorption of the refrigerant vapor on a solid surface, which is potentially simpler, smaller, and cheaper to operate than absorption systems. Research suggests that, for low hot-water temperatures, comparable performance between absorption and adsorption systems can be achieved, for typical July conditions in Phoenix, Arizona. Importantly, the working fluid in the adsorption system can be ordinary water, instead of the hazardous refrigerants utilized in absorption systems. We are designing and constructing a prototype solar-powered adsorption cooler, initially aimed at residential applications.