Analysis On Solar Linear Fresnel Collector And Medium Temperature Thermal Storage System

In this paper, for the solar medium temperature thermal technology, Linear Fresnel lens solar collector and thermal storage were studied. A linear Fresnel collector was designed and established. Then, the optical, heat loss and thermal efficiency of Fresnel lens collector were defined, and the maximum of optical efficiency was 75.5% by Trace-pro optical software. Meanwhile, the light trace of Fresnel lens mirror was modeled, the optimized relation of mirror's width, receiver's height, beam's width and energy density were studied. Then, The 14.4m2 prototype of Fresnel lens solar collector was established, the test result showed that the practical optical efficiency is 55.7%, the efficiency of collector is 36.6% at 150℃and the heat loss of the receiver is 110.0w/m。Furthermore, in order to find a suitable the thermal storage for medium temperature solar collector, mixture material of quartz sand and steel shot , KNO₃/LiNO₃ molten salt and solid phase change material were studied. Then, a composite material comprised of solid phase change material and expanded graphite was developed and its heat conductivity was increased 6 times. Finally, a 2kWh sensible thermal storage which is combined with serpentine heat exchangers was established. According to the thermal efficiency, exergy efficiency and collector efficiency, the results showed that the thermal efficiency of heat storage is about 81.3%, exergy efficiency is about 51.3%, The optimized thermal storage volume-to-parabolic trough collector area ration is 80L/m2 by coupled heat transfer model, and the desired heat transfer area could reduce a lot when the heat conductivity increases to 2.0 W/(m·℃). The solar indutrail thermal application could benefit from the above conclusion.