Solar-powered air conditioning combines a solar energy system with a refrigeration unit, using the heat generated by solar collectors to drive the refrigeration system. Air conditioning usage is highest when the weather is hot and solar radiation is strongest, making this the most opportune time to utilize solar-powered air conditioning.
Currently, there are two main methods for utilizing solar energy for cooling: one is to first achieve photoelectric conversion and then use electricity to drive a conventional compression refrigeration machine; the other is to perform photothermal conversion and use thermal energy for cooling. Because the former is expensive, researchers mainly focus on developing solar-powered air conditioners using the second method.
Working principle of solar-powered air conditioning
The working principle of a solar-powered cooling and air conditioning system is as follows: First, several mirrors concentrate sunlight onto the pipes, heating the water flowing through them. The energy generated by this hot water then powers a chiller containing cold water, which in turn supplies the chilled water needed to produce cool air to the air conditioner. When there is no sunlight, natural gas can be used as an energy source.
Unlike direct solar-to-thermal conversion, solar-powered air conditioning involves a solar-to-thermal/electricity-to-cooling conversion process, effectively utilizing solar energy indirectly. It is not as easily achieved as direct low-temperature utilization such as hot water or drying, and is technically more complex. Besides requiring a relatively high solar energy temperature as its power source, it also necessitates an energy conversion process through a refrigeration cycle.
The biggest advantage of using solar energy for air conditioning is its excellent seasonal adaptability; the hotter the weather and the better the solar radiation, the greater the cooling capacity of the system. This characteristic has led to the attention and development of solar cooling technology. Solar cooling can be achieved through various pathways, including "light-heat-cooling," "light-electricity-cooling," and "light-heat-electricity-cooling."
Application of solar-powered air conditioning
Solar-powered cooling and air conditioning systems must be designed to accommodate both heating and air conditioning applications. Ideal applications include office buildings, guesthouses, schools, hospitals, and swimming pools. These users require heating in winter or year-round, such as for domestic hot water, heating, and swimming pool water replenishment and temperature control. In summer, they generally require air conditioning. Solar energy can be used to provide the large amount of domestic hot water needed daily throughout the building. In addition, solar-powered hot water can be used for cooling on one floor during the summer.
The solar-powered air conditioning and hot water system uses flat-plate collectors to collect solar energy and generate hot water, which is stored separately in cooling and domestic hot water tanks. During operation, solar energy is prioritized for the cooling hot water tank, where the temperature is higher than that of the domestic hot water. Chilled water at approximately 9°C, produced using a central air conditioning system, is delivered to the user's fan coil units and then returned to the chilled water tank. In case of inclement weather or insufficient water temperature, an oil-fired hot water boiler is used for auxiliary heating to ensure the system can operate around the clock. Domestic hot water is directly supplied to users, and the system automatically collects data and controls its operation.
