Study Of The Solar Ejector And Direct Evaporation Combined Cooling System Powered By Photovoltaic Solar Energy

Solar photovoltaic and thermal refrigeration technology has been attracting more and more attention,based on the previous studies of ejector refrigeration system,this paper presents a "Zero Energy" refrigeration system-solar ejector and direct evaporation combined cooling system powered by photovoltaic solar energy.Pump and fan are only component consuming electricity in the direct evaporative air-conditioning,its power consumption is small and coefficient of performance is high when compared to mechanical refrigeration.But the relative humidity increase and efficiency reduce along with the running time growth.The main innovative points of the dissertation were that it proposes a solar ejector and direct evaporative combined cooling system with a high coefficient of performance and uses solar to provide heat and electricity to start the system,it could balance supply-demand between cooling capacity and the air conditioning load issues and has the features of saving in energy.This system is applicable for the area where is dry and rainfall is quite low in summer,temperature difference is bigger.In this thesis,performance of the combined cooling system used R141b as refrigerant is studied and combined with the TRNSYS software analysis system.Optimal structure of ejector is designed with Sokolov's model and gas dynamics theory,one-dimensional cross-section and constant pressure mixing model was established based on the law of conservation.The calculation results with the experimental data and theoretical analysis to compare verification.The indoor temperature and load of the mobile workstation is simulated by the TRNBuild software,and the dynamic energy consumption and indoor air-conditioning room temperature would be calculated.Proposed system is divided into periods run:8:00?12:00 direct evaporative cooling air conditioner is used to cold the building;12:00?17:00 in the air conditioner efficiency decreased period,solar ejector refrigeration system is started;at night natural ventilation is used to remove indoor cooling load.Solar ejector and direct evaporation combined cooling system powered by photovoltaic solar energy makes full use of solar energy,part of the light energy is applied to heat transfer in the heat storage tank,the heat that cooling subsystem ejector required is provided by storage tank and generator through the heat exchanger;in addition solar panels provide power to the pumps and fans,and the excess energy is stored in batteries.In this paper,TRNSYS is used to simulate solar photovoltaic power system and solar collector system,respectively.The size of solar panels and the battery capacity is designed according to the system needed power.The impact of occurred circulating pump start temperature and collector area for heat storage tank is analyzed by the calculated collector parameters and heat storage tank temperature of TRNSYS simulation.The performance of the system such as the cooling capacity,power consumption,coefficient of performance,etc.was analyzed.The results show that,under the same cooling load condition,daily electric power consumption of compression refrigeration is 2.27 kW·h;ejector refrigeration is 1.39 kW ·h;direct evaporative cooling air conditioner is 0.55 kW · h.By the calculation,daily electric power consumption of Solar ejector and direct evaporation combined cooling system powered by photovoltaic solar energy is 0.955 kW · h,the combined refrigeration system is only 42.07%of daily power consumption of compression refrigeration.Its coefficient of performance can be at almost 4.43 times as large as compression refrigeration system.Summer electricity of compression refrigeration is 139.47 kW · h;ejector refrigeration is 86.4 kW · h;combined Refrigeration System is 63.55 kW· h,the combined refrigeration system is only 45.57%of compression refrigeration in summer,moreover,the ejector refrigeration sub-system use 80.8 percent of the combined refrigeration system.The capacity of Solar ejector and direct evaporation combined coolling system powered by photovoltaic solar energy can completely meet hourly cooling load of the building in summer.The system can operate independently under the conditions of right solar panels and collectors.