Study on Seasonal Adjustment of Solar PV Tilt Angle around the North of 45th Parallel

The tilt angle of the small scale existing solar power plants is 60 degree and it is 45 degree for the megawatts (MW) class solar power plant in Mongolia. However, the PV module which is installed with 45 degree accumulates lots of snow during the winter. Currently, all solar PV systems installed in Mongolia are fixed the direction and tilt angles. According to the previous research result, the tilt angle of those systems was not suitable for using especially in the winter. The PV module which is installed with 60 degree does not accumulates snow even during the autumn and spring. According to the National Aeronautics and Space Administration (NASA) solar radiation database, solar irradiance for equator facing is largest at 32-degree tilted angle during the summer, 47-degree during the spring and autumn, at 62-degree during the winter. The results of this paper show, the tilt angle of the PV module should be adjusted at least twice a year. For instance, the tilt angle will be adjusted at the 32-degree from 15th March to 24th August, at the 62-degree from 25th August to 15th March. In this case, the annual total energy output will be increased up to  30% than present production.