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A study on the thermal physical property of kind of phase-change heat storage materials is carried out to explorer the feasibility in the solar thermal storage area. Using the compacting-melting-absorbing-cooling method, the composite material of PE, PG and expanded graphite are made, the thermal conductivity of which is tested by the laser thermal conductivity tester. The results show that rising the content of the expanded graphite in the composite material will increase the heat conductivity coefficient in different directions respectively. This paper describes the preparation method and physical property test of the PE/PG- expanded graphite composite phase change material. The test results shows that the thermal conductivity in each direction of the material rises with the increase of the content of the expanded graphite in the composite.

A Fresnel solar collector with triangular cavity absorber is introduced and the performance tests are carried on. The Fresnel collector is consisted of a cavity absorber with tube rows, a mirror field with flat glass, and the trace system in homotaxial manner. According to relative technical standards, the transient method is used in the performance tests. Based on the test results, the no-load coefficient, the heat loss coefficient and the thermal efficiency of the collector are calculated and analyzed. The result shows that the thermal efficiency is up to 36.6% and the heat loss coefficient is 110W/m.

The optical losses of the Fresnel collector's mirror field are analyzed mathematically and optimization for the design parameters is made. In analysis of the optical characteristics, the optical losses of different segment are described according to the optical principles. And the optical efficiency is derived from the losses description. Finally, the influences brought on by the mirror field parameters, such as the height of the receiver, the width of the mirror and the interval between adjacent mirrors, are showed up respectively so as to guide the optimal design.