Analysis And Evaluation Of Electromagnetic Environment Near The Ground Receiving Station Of The Space Power Station

With the increasing demand for energy worldwide,the concept of solar power satellite had made it possible to fully develop and utilize space solar energy.As solar power satellite needs microwave power transmission technology to transmit power to the ground,similar to traditional energy(coal / petroleum / nuclear energy),solar power satellite would inevitably affect the earth’s environment.In particular,microwave power transmission used high-power microwaves to penetrate the atmosphere at a fixed location for a long time and illuminated the ground receiving station for a long time.Therefore,we must research and analyze the environmental impact of solar power satellite.Because the transmitting antenna would affect the power density at different positions of the ground receiving antenna,I calculated the relevant parameters of the solar power satellite system combining ground power transmission.Thereby,I designed a parabolic reflector antenna with a diameter of 875 m and the feed source of a pyramid horn antenna.Then I calculated the far-field radiation characteristics of the reflector antenna theoretically,and simulated the miniature model of the reflector antenna using electromagnetic software HFSS with the FEM-IE-PO hybrid algorithm.The simulation results verified the validity of the theoretical calculation.Considering that the radiation power of transmitting antenna reached GW level,the radiation power of single feed antenna would be limited.Therefore,I simulated uniform planar arrays of different array elements,including pyramid horn,waveguide and half wavelength dipole,then chose the dipole antenna as a planar array element model,which could achieve the radiation characteristics similar to the parabolic reflector antenna.At the same time,I analyzed and calculated the impact of free space loss,atmospheric absorption loss,rainfall attenuation,and ionosphere on microwave transmission.Among them,free space propagation loss is the main influence.According to the total transmission loss of the microwave and the simulation results of the transmitting antenna,I calculated the power density of the center position and the edge position of the receiving antenna to verify the correctness of the whole system design.Next,I simulated the field strength at the center and the edge of the receiving antenna by dividing the radiation area of the transmitting antenna.When a uniform plane wave was perpendicularly incident,the field strength at the center of the receiving antenna didn’t exceed 868.4V/m,and that at the edge didn’t exceed 173.6V/m.Finally,according to the management standard of electromagnetic radiation exposure limit,I proposed the safe area of the public,medical equipment and communication system by the aperture field method based on the equivalent principle.If the operating frequency of the solar power satellite was 5.8GHz and the transmitting antenna field is 10 d B gaussian taper distribution,the public exposure area and the safety area of the rail transit equipment should be at least 4.40 km and 10.54 km away from the center of the receiving antenna respectively.Considering that the frequency band of the microwave power was same with the frequency band of WLAN communication system,and the intensity of electromagnetic field was still high compared with the intensity of WLAN signal in the public exposure area and the safety area,WLAN communication system maybe couldn’t operate normally.