Solar cooling systems

Abstract

Due to a large amount of greenhouse gas emissions caused by burning traditional fossil energy resources, the environmental temperature has increased year by year, which has led to the yearly increase in the demand for air-conditioning. However, the conventional air-conditionings driven by grid power are the main products in the global market. Besides, using electric air-conditioning increases electrical pressure in peak times. In order to alleviate the contradiction between power demand and supply, more thermal power stations have been built, and more fossil fuels have been burnt in the past decades. In this context, more greenhouse gas has been discharged, and a vicious cycle has emerged between power generation and greenhouse gas emissions. Therefore, the refrigeration driven by solar energy has become one of the promising approaches to reduce or partially replace conventional refrigeration systems under the pressure of environmental protection. Solar thermal refrigeration and solar photovoltaic refrigeration are two main refrigeration modes in the field of solar refrigeration. Under this background, a solar-powered adsorption cooling system was designed and optimized. The performance test results show that its maximum cooling efficiency was 0.122, and it could make 6.5 kg of ice at most daily. The cooling efficiency of the solar-powered adsorption refrigeration system with valve control in the adsorption/desorption process was significantly higher than that without valve control. A 23 kW single-effect LiBr-H 2 O absorption chiller driven by PTC was investigated as well. The results reveal that its average refrigeration coefficient n r,av was between 0.18 and 0.60, and the average coefficient of performance (COP) of the whole refrigeration cycle COP s,av was between 0.11 and 0.27 under different weather conditions. In the mode of photovoltaic refrigeration, PV refrigerator and PV air-conditioning system were studied through experiments. PV refrigerator was mainly powered by photovoltaic module on sunny days and battery bank on overcast days. When the freezing room of the refrigerator was crammed with 5 kg, 6 kg, and 7 kg of water, the COP of this system was 0.24, 0.29, and 0.34, respectively. The 1.5 HP steam compression airconditioning driven by PV array was built, and a 1-year investigation on its operation performance was made through an experiment. The research results indicate that the 1.5 HP steam compression type air-conditioning could be independently driven by PV array when solar irradiance was higher than 675 W/m 2 . On sunny days, the air-conditioning system could be completely driven by PV array for about 4 h per day. All its daily average COPs were about 0.35, and daily average guarantee rates were between 0.93 and 1.25.