Study On Heat Storage Material For Solar Energy Prepared By Desert Sand

As energy shortages and fossil energy exhaustion has become a worldwide problem,it is imminently to develop new energy. Solar energy has three advantages which is universality, limitlessness reserves and cleanability. Based on the three advantages,solar thermal power generation has aroused wide attention of international researchers.The thermal storage of solar thermal power generation system can store heat under normal illumination to keep thermal supply when illumination is insufficient or in the night, to make sure the normal power generation is in normal operation. Our country not only facing serious energy problem, but also facing serious ecological environment problems such as desertification, the country's desert area up to 64×105 km2 now, however desert areas have the advantages of long-time sunshine and rich in solar energy resources. This subject uses local materials to prepare solar heat storage materials,desert sands were used and the regenerator unit structure was designed, so as to create economic benefit and realized the ecological protection and common development of using solar energy at the same time.In this paper, the desert sand, shale, calcite, potash feldspar, albite were used as the main raw materials, prepared the Ca-Al-Si system ceramic honeycomb with extrusion methods. Using XRD (X-ray diffraction), SEM (scanning electron microscope) and other modern analysis techniques tested the relationship among the formula of material composition, preparation process, microstructure and properties. Based on the best formula A5, designed and prepared high-temperature encapsulant and discussed different filling methods of phase change aterials in honeycomb ceramic, calculated heat storage density of latent-sensible heat composite ceramics. Based on latent-sensible heat composite ceramic studied in this paper and previous research results, designed the accumulator unit of solar thermal power accumulator, connecting way of heat storage units, and structure size of honeycomb ceramic. The results showed that Ca-Al-Si system honeycomb heat storage ceramic meets the demands of heat storage subsystem in solar thermal power generation system, structural design of heat accumulator unit is reasonable.The study of series A shows that the introduction of feldspar reduced firing temperature of sample, The fluxing action of feldspar is more obviously with calcite decreases in a certain range. The firing temperature range of series A is at 1040～1060℃, the range of porosity, water absorption, bulk density and bending strength are 31.26～47.46%,17.32～33.41%, 1.45～1.81g·cm-3 and 30.35～58.27MPa respectively. Formula A5 fired at 1060℃has the best properties, with the composition of desert sand 50%, Shandong shale 20%,Daye calcite15%,Linzhou albite 5% and Shandong potash feldspar 10%.The porosity, water absorption, volume shrinkage and bending strength of sample A5 is 31.26%,17.32%, 1.81g·cm-3 and 30.35MPa respectively, the samples did not crack after 30 times thermal shock tests(room temperature to 800℃). The main crystalline phases determined by XRD are tridymite(SiO2), anorthite, calcium silicate. The microstructure was observed by SEM. A lot of tridymite with the size about 0.2μm and calcium silicate with the size 1.5～4μm were found on the surface of anorthite and anorthite as skeleton were bonded by glass phase, these increase the strength of the samples. Lots of granular scales quartz relative to cristobalite have smaller volume change in the burning into and cooling process, improve strength and thermal shock resistance of the samples, meet the demands of thermal shock resistence solar thermal power generation.To explore the feasibility of using desert sand preparation ceramic honeycomb, basing on the best formula A5 for extrusion tests. Added some moderate binder, plasticizer, lubricants and water to the formula A5.For safe and reliable encapsulation PCM, encapsulate agent was studied, high-temperature packaging agent used for composite honeycomb ceramic was prepared, it was prepared from the fomula referred above by adding some components of flux as high temperature binder, phase change materials NaCl was encapsulated in the honeycomb ceramic. The influence of the way of filling and content of NaCl on the thermal storage density was calculated. The SEM analysis sho wed that the binding property of the package agent and matrix material is good.Designed a solar thermal power generation regenerator unit, this will ground for "Ca-Al-Si" system ceramic honeycomb used in the heat storage subsystem of solar thermal power generation system.The structure of heat storage unit is reasonable structure, efficiency of heat transfer is high, economic benefit is good, reaches the preliminary design requirement, suitable for solar thermal power generation heat storage subsystem.