Investigation On Solar Heat Accumulator With Composite Phase Change Material

As a kind of resources,solar energy has gained more and more attention by every country for its clean, uniqueness, infinity. Solar energy utilization technology and PV solar power technology are becoming to mature and widely used in the industry and the lives of people. Converting solar energy into heat can satisfy people’s growing demand for energy. So that study on solar collectors become an important aspect in solar energy using. While solar energy is not a stable energy, storing it temporarily may use the thermal energy storage technology which has large latent heat value and widely used.Through the investigation on solar energy utilization and heat storage technology at home and abroad, a high thermal conductivity, high phase change latent heat value, stable performance and high phase transition temperature inorganic salt/expanded graphite composite phase change materials is used to combined with groove collector in order to solar thermal conversion and heat storage.This article adopts the method of physical mixing for the proportion of the expanded graphite and LiNO3/KCl is 1:2:2. Differential scanning calorimeter(DSC) and Hot-disk are used to characterize the materials’ thermophysical properties. The results shows that the melting and solidification temperature are 165.5oC and 159.94 oC, while the enthalpy of melting and solidification are 179.4J/g and 155.3J/g, Solid specific heats is 0.6019J/(g?oC) and liquid specific heat is 1.4812 J/(g?oC). The average coefficient of thermal conductivity is 9.44W/(m?K) when the material is pressed into the density of 0.8 g/cm3.According to structure characteristics of the solar trough collector purchased in Himin Solar Energy Co., LTD and the heat utilization plan, We design special model tool to compress the composite phase change material into block, then fill block composite phase change materials into collector tube in order to constitute solar thermal storage device. Testing the influences of different illumination intensity and flow rate, experimental results show that: as the light density increases, the heat accumulator can achieve a highest temperature, and the storage quantity of heat of phase change materials is also increasing; the highest temperature can reach 250oC; the highest temperature is influenced by light intensity and the thermal insulation performance of the heat accumulator; when the amount of cooling water increased, heat release rate of the heat accumulator increased, but the influence of cooling water to the heat release rate gradually reduced.Paper studies have shown that Li NO3/KCl-EG composite phase change materials combined with solar trough collector can solve the problem of solar energy used in medium temperature heat utilization. The material has high grade energy, so that it is suitable for industrial heating process, drying, building heating, and other fields.