Solar-powered absorption chillers are based on a technology that’s been in use in commercial A/C and refrigeration for decades. Absorption cooling uses the heat-extraction properties that result from condensing a solution of water and ammonia. It utilizes no environmentally unfriendly chlorofluorocarbons refrigerants and few moving parts. When combined with solar power as the energy source in a dry climate, an absorption chiller can provide very low operating costs and very small environmental footprint.In a standard air conditioner, an electrically powered compressor concentrates the heat energy in refrigerant. In an absorption heat pump, ammonia is evaporated into vapor form and acts as the refrigerant that extracts heat. After the ammonia has released its heat load through the condenser coil, it is absorbed into a solution with water. For the cycle to repeat, the water must be heated to a temperature high enough to boil the ammonia out of the water. In conventional absorption chillers, the heat source may be a natural gas flame. In solar-powered absorption chillers, it’s the heat of the sun.
To achieve the 190-degree temperature required by the process, special solar collector panels incorporate tubes that circulate water. These panels are usually mounted on a rooftop for maximum exposure, much like solar photovoltaic panels for generating electricity. Called concentrated collectors, the panels incorporate mirrors to focus the heat of the sun on the tubes circulating water and feature special glazing and insulation for maximum heat gain. Concentrated collectors function most effectively in dry, hot climates where transfer of the sun’s heat to the water tubes is most efficient and the highest temperatures are generated.
Only a small amount of electricity is used by a solar absorption chiller since the process involves no compressor—a major power drain in a conventional system. Power is consumed only by circulation pumps that draw low amounts of current, plus the system blower fan.
Wolff Mechanical Inc. is a full-service cooling and heating provider to homeowners in the greater Phoenix area. Contact us for more information about the potential of reducing cooling costs with solar-powered absorption chillers.
Our goal is to help educate our customers in the Phoenix Valley area of Arizona about energy and home comfort issues (specific to HVAC systems).