Performance Investigation Of A Solar Absorption Cooling System Driven By Fresnel Solar Collector With Thermal Storage

Solar energy is the most widely used among all kinds of renewableenergy. Solar heating and cooling is an indispensable way to realize thelarge-scale and low-cost utilization of the solar energy. The airconditioning system driven by the solar collectors could integrate tightlywith the solar hot water and heating system which are applied widely atthis moment. The solar comprehensive system introduced in thedissertation includes solar collecting system, energy storage system andair conditioning system. In the essay, the experimental and simulationstudy concentrating on the three systems will be introduced. The mainworks are summarized below:(1) As for the solar collecting system, the array constructure and sizeof the total550square meters Fresnel collectors was put forwardaccording to the design process. The theoretical study of the opticalperformance is carried by virtue of the Monte Carlo simulation method.The optical efficiency can reach up to61.58%. The factors which affectthe optical performance were analyzed. Furthermore, the thermalperformance was predicted by employing CFD method. The radiativeheat loss from cavity receiver was found to be the dominant model of thetotal heat loss. As the operating temperature increases from100°C to220°C, the total heat loss increases from93.6W/m to339.6W/m, heat losscoefficient increases from38.9W/m2K to55.6W/m2K and the thermalefficiency decreases from58%to48.5%.(2) As for the energy storage materials, the molten salt(7%NaNO3-53%KNO3-40%NaNO2) was chosen as the appropriatematerial for the system. a host matrix of expanded natural graphite (ENG)has been used to enhance the thermal conductivity of the molten salt. theresults showed that the highest effective thermal conductivity ofconsolidated PCMs was24.5W/(mK), which was53times higher than ordinary salt powder, thermal conductivity of which is0.46W/(mK)and the practical and easy preparation process was put forward.(3) In terms of the design work of the energy storage system, themathematical model basing on the enthalpy method is used to simulatethe actual heat exchange process with the help of FLUENT. The heatexchange stages can be deduced from the simulation graphs and the thesimulation results were validated by the experiment data.Simultaneously,the effect on the energy storage performance brought by the temperatureand velocity of the heating fluid is studied.(4) The performance prediction was built through the simulationcompleted by the TRANSYS software. On a typical day in Shanghai, Byusing the automatic switch LiBr absorption chiller, the solar airconditioning system can operate continuously about6to8hours and theaverage COP could reach up to0.8.