Organic silicon used for solar heat transfer mediu...

Organic silicon used for solar heat transfer medium       Solar energy is a new energy inexhaustible, be inexhaustible. According to estimates, the total power of the earth receives solar energy for 173*10^15 watts. The energy in the received, are absorbed by the atmosphere about 23%, reflected back into space accounted for 30%, through the atmosphere to the earth's surface accounted for 47%, about 17 trillion kilowatt.      At present, there are solar photovoltaic, solar thermal power generation and solar water heaters and other aspects of the use of solar energy, the former is the use of silicon photovoltaic cells directly convert sunlight into electricity; the latter is by means of heat transfer oil obtained from the solar heat collector, then the quantity of heat to generate steam boiler room, drive a turbine generator.       Solar thermal power generation heat collector system, usually by the system, the steam generator and the electrical system consists of four parts. Heat transfer oil plays a circulating heat transfer function in the four system, it directly affects the performance of solar thermal power station efficiency and cost. At present, for the solar heat collector has four commercial heat transfer oil: Poly alpha olefins, ethylene glycol aqueous solution, propylene glycol water solution and the organic silicone oil.       In the four kinds of heat transfer oil, silicone oil is the best economic and performance. Despite its initial cost is higher, but in the long run, organic silicone cost the province, this is because the organic heat transfer oil has the following advantages: 1, high heat transfer efficiency, good thermal stability, every hour can absorb 68000 British thermal units of heat from the collector. Due to high heat transfer efficiency, can make the efficiency of steam turbine is increased by 14%. 2, the use of high temperature, the use of ordinary heat transfer oil temperature is 600 ° F, and silicone oil, heat transfer oil can be effectively operated at a temperature of 700 to 750 DEG F. Due to the thermal efficiency and the use of high temperature, so that the total surface area of solar collector is reduced by 27%. 3, long service life, in spite of ethylene glycol water solution of low cost, but due to its short service life, with half of the 2 to 4 years will be the replacement of the new oil; life and silicone oil, heat transfer oil can be as high as 25 years. 4, repair costs, due to chemical inert silicone oil, no corrosion to equipment, therefore does not need auxiliary facilities or uses the high quality material to prevent heat transfer oil condensation, overheating and corrosion phenomenon; and the use of ethylene glycol water solution requires regular maintenance. In the solar thermal power generation system, how to realize the solar heat storage is to carry out a comprehensive utilization of solar energy is the key, this is because the solar energy reaching the earth, a fixed point of the resin is changing; summer solar, solar energy in winter, during the day, night, solar energy is No. Power user demand for electricity is continuous and constant, the solar energy when the strong heat, sometimes function without affecting the practicability of solar thermal power generation. Later, Virginia, a solar energy company invented a "storage pool", it is the use of a special kind of hydrocarbon liquid, can a smaller volume to store large amount of energy. This became the "hydrothermal" hydrocarbon liquid is made with petroleum products waste, borrow a cheap, very stable at high temperatures. The specific heat of 0.71 BTU / lb ° F, every kilograms of this "hydrothermal" 92000 card can store solar energy, equivalent to 1 kilograms of water required by 8 ℃ boiling heat. There is a characteristic, it is stored solar energy is very stable, not influenced by the external temperature changes, not easy. The most commendable is, this kind of "liquid" thermal energy conversion rate is very high, can reach 30% to 40%, and the silicon solar energy conversion rate is only 10%.