A Study On High Temperature Solar Thermal Utilization And Heat Storage Technology

The utilization of solar energy in medium and high temperature is a completely clean way of generating electricity without secondary pollution. Due to the discontinuity of solar radiation, to ensure the continuity and stability of electric power, thermal energy storage system is essential. However, small-scale solar thermal power plants and thermal energy storage devices are not sufficiently researched.The paper carries out the following researches on thermal energy storage device of small-scale solar thermal power system:uses software to model and simulate the energy consumption of villas in Nanjing; designs and calculates the thermal energy storage system; establishes the physical and mathematical model of molten salt thermal storage tanks; uses ANSYS to simulate and analysis the factors impact storage tanks’characteristics for both hot tank and cold tank. The main results are as follows:1. Calculated sizes of the molten salt tank for a 6h solar thermal energy storage system which designed capacity is 400kW, thermal storage temperature is 292～386℃: the radius is 7.2m, the volume is 204m3 for hot tank and 200m3 for cold tank.2.The sidewall insulation affects the temperature distribution in molten salt, while the top insulation affects the temperature of air above the salt; the edge of the tank’s bottom needs to strengthen the heat transfer and insulation; the thickness of the designed tank recommended is 0.4m for hot tank and 0.3m for cold tank.3.The core of the tank is at the same temperature, along the height distributing in 0.66m-3.25m for hot tank, and 0.33m-3.20m for cold tank, thus the suction inlet location of molten salt pump is no less than 0.66m and 0.33m for hot tank and cold tank, respectively.4.As storage temperature increases, heat loss of the heat storage tank shows an upward trend, but the growth rate becomes slow, as a result, maximize the heat storage temperature as conditions permit. Since the steam temperature is generally above 370℃, the heat storage temperature should not be lower than 380℃.5. The total heat losses of the tank reduce, and then increase with the increasing height-diameter ratios, the minimum is at the value 1.4. When ambient temperature rises from -5.2℃ to 37.2℃,the heat losses linearly decreases, so auxiliary heating device is needed to prevent the temperature being too low. As wind speed increases from 0 to 11 m/s, the heat losses show increasing trend.This paper simulates and analyses the factors that affect the temperature distribution in molten salt and heat losses, and provides instructive recommendations for designing small-scale molten salt thermal storage tank used for generation.