Simulation And Experimental Study Of High-temperature Air Solar Collector And Ceramic Thermal Storage

Clean and renewable energy is an effective way to alleviate the energy crisis and environmental problems. Solar energy has been paid more and more attention because of being clean, renewable and abundant. Concentrating solar power (CSP) technology makes a stable power supply if thermal energy storage system is integrated. Futhermore, a higher temperature of working media always brings a higher efficiency of CSP. In this thesis, a solar power generation system based on a high temperature air solar collector is proposed, combining with high temperature thermal energy storage, and numerical simulation and optimization is carried out based on the experimental study.Three kinds of solar air receiver were studied, including a volumetric receiver using ceramic foam as absorber, a coil cavity receiver and a combination of the above. The experimental study was conducted in an indoor solar simulator system. The results show that the outlet air temperature deceased and the thermal efficiency increased when the flow rate increased. The outlet air temperature was higher by ～100℃ when the flow direction was downward than that of upward flow. The thermal efficiency of the combined receiver was higher by ～18% than that of ceramic volumetric receiver. For the combined receiver, the outlet air temperature could be up to ～604℃ at 1m3/h and the thermal efficiency up to 70.9% at 7m3/h.An optical simulation using ASAP software was conducted firstly. The energy distribution of focal spot was obtained based on the optical model of solar simulator system. Then the actual energy distribution of focal spot was detected using a Lambert plate test system, and then the optical model was checked and impoved. The spot energy distributions of the three air receivers under solar simulator system were calculated by the optical model. A heat transfer model was build to couple with the optical model, and the actual spot distribution was set to be the boundary condition of heat transfer. The simulation results matched well with the experiments’, and the deviation was within ～5%. The numerical results show that the outlet air temperature decreased linely with the increase of flow rate, while the thermal efficiency increased. The outlet air temperature increased and thermal efficiency decreased with the increase of incident intensity. When the air flow increased from 1m3/h to 8m3/h, the heat loss of each part decreased and the thermal efficiency of combined receiver increased from 17% to 75.9%. The thermal efficiency of combined receiver was higher than that of the foam ceramic receiver. The radiation and convection heat loss of the shell wall was the greatest. With the increase of incident intensity, the heat loss of each part increased, while the thermal efficiency decreased. With the increase of the thickness of insulation, the heat loss through the shell wall could be reduced significantly, e.g. by 36% for 10cm and by 52% for 15cm compared to 6cm, respectively.The characteristics of high-temperature sensible thermal energy storage were investigated using honeycomb ceramic. The temperature distribution of storage material and the air outlet temperature were obtained. The experiment results show that a ～2h charging period could afford a 30-min effective discharging period, and the experimental efficiency was about 66%. The simulation model was built based on the experimental results, and the error was within ～5%. The effects of different thermo-physical parameters and geometry parameters on the thermal performance of thermal energy system were dicussed using the simulation model, which indicated an 8h discharging period could be obtained when the geometric and operating parameters were optimized and the efficiency of TES reached up to 90%.The performance of integrated systems were dicussed, including a solar dish-Stirling power system combined with high temperature thermal energy storage based on dish two-stage concentrator and a solar thermal power generation system combined with a micro gas turbine. The generation efficiency of the former was about 14.3%～22.4% and the total thermal efficiency could reached up to 65%. For the latter, the input portion of solar energy could accounte for 36.4%～50.6%.