The Study Of The Influences Of The Phase Change Heat Storage On The Operation Properties Of The Solar Chimney Power Plant System With Vertical Heat Collector

Due to the heat collector covers great area, the traditional solar chimney power plant system can only be built on the desertification area. The very high chimney is difficult to be built and keep stable. On the basis of traditional solar chimney power plant station, a new kind of system with vertical heat collector is designed. The solar chimney power plant system with vertical heat collector combines the chimney and heat collector, attached to the high-rise buildings, which greatly reduces the area of original design and expands the application of this simple and clean power plant technology to cities. Because the solar radiation is intermittent and instable, the heat storage layer made of paraffin phase change material is added to the system to improve the energy efficiency and guarantee the continuous working of the system. The influences of phase change heat storage on the system operation properties and the heat transfer strengthening methods between air and paraffin are studied.Unsteady conjugate numerical simulation of the air flow and phase change heat storage in the system is done. The air maximum velocity and system maximum power in the condition of no heat storage layer or having heat storage layer are compared and the influence of thickness of heat storage layer on the system operation is analyzed. The conclusions include: the changing relationships of air velocity and system power with time are similar to the change of solar radiation with time; when the solar radiation reaches to the maximum value, the air velocity and system power also have their maximum values. The air velocity is 0.79m/s and the system power can be 1.3W at night in the system with heat storage layer. At noon the maximum power of system with heat storage layer is lower than that of system without heat storage layer, but because of the energy-storage role of paraffin, the power increases along with the increase of days, so does air velocity at night. Therefore the heat storage layer can make the system run continuously. The effects of thickness of heat storage layer on the air velocity and system power are compared. When the thickness is 0.2m, the system maximum power is bigger. So the thickness of heat storage layer in the system can be set as 0.2m.Because paraffin and air has low heat-conducting coefficient, different surface forms of heat storage layer are designed in order to enhance the heat transfer between the air and paraffin, and their abilities of heat storage are simulated and compared. The results show that the increase of contact area between air and paraffin can strengthen the heat exchange between them; when longitudinal rectangular fins are added to the surface, the melting or solidification time of paraffin reduces greatly, the air velocity is enhanced, so the continuity of system operation is ensured. The influence of adding nanoparticles to paraffin on the heat storage process is analyzed by numerical simulation and the heat storage ability of phase change materials in the solar chimney power plant system with vertical heat collector strengthened by the nanoparticles is prospectively studied.