Experimental Investigation on a Closed-Cycle Solar Adsorption Cooling System

摘要

Solar cooling has been an attractive application for solar energy because of the near coincidence of peak cooling load with the available solar power. Currently, most of the solar cooling systems commonly used are the hot water driven lithium bromide absorption chillers or adsorption chillers. Some theoretical analysis and experimental investigations have been done to study the performance of solar cooling systems. The existing solar cooling systems, either solar absorption cooling systems or solar adsorption cooling systems, are always open-cycle systems. These systems include the heat storage water tanks which accumulate heat by solar collecting circulation. The chillers are then driven by the hot water from the heat storage water tanks. So far, few reports have been found to be closed-cycle systems. Compared with an open-cycle system, a closed-cycle solar cooling system has the advantage of simplicity because of nonuse of the heat storage water tank. In such systems, the chillers are directly driven by the hot water from the solar collectors. In this paper, a closed-cycle solar-powered adsorption cooling system was designed. The system was mainly composed by the evacuated tubular solar collectors with the area of 150 m2, two adsorption chillers with the rated cooling capacity of 15 kW, a cooling tower, fan coils inside the air-conditioned rooms and circulating pumps. The experiments were carried out to study the operating characteristics and performance of the closed-cycle solar adsorption cooling system. Solar energy is a typical variable heat source; furthermore, the adsorption refrigeration is characteristic of period and variable behavior. Consequently, it is found that the operation of the closed-cycle system presented wave character because of low water capacity of the system. The water temperatures of the inlet and outlet of solar collector array cyclically swung since the water entering the solar collector array was directly from the adsorption chillers. Besides, the inlet water temperature of the adsorption chillers varied distinctly. However, the cooling effect of the closed-cycle solar adsorption cooling system was satisfactory. Moreover, compared with the open-cycle system, the closed-cycle system has the advantage of higher electric COP because of reduced use of the circulating pumps, which is meaningful in the energy conservation of solar cooling systems.