Searching suitable areas for installing solar panels in Golestan province using observation, ERA5 and GEOS-5 data

Due to its special geographical location, Iran has a high potential for the use of renewable energy. At present, electricity in Golestan province is supplied from Neka and Aliabad Katoul power plants, which due to the increase in population, it is necessary to build new power plants. In this study, the annual and monthly solar energy atlas maps were prepared using solar radiation data recorded in meteorological stations, GEOS-5, and ERA5 data to help decision-makers to locate suitable places for the establishment of solar power plants in different parts of Golestan province. In recent years, along with other kinds of data, the use of reanalysis data of numerical forecasting models has become popular, especially for those areas which are not covered by satellites and also to fill data gaps. To reach the goal of this study, statistical gaps in meteorological station data in the selected period (from 2014 to 2020) have been filled using the ratio method; then RUN-TEST method has been used to test the homogeneity of the data. To check the accuracy of data, the Absolute Error (MAE), Mean Bias Error (MBE), Mean Square Error (RMSE), and Coefficient of Determination (R2) between actual radiation values and GEOS-5 data as well as ERA5 data were calculated. The results show that although the accuracy varies across different locations and periods in the province, in general both outputs are suitable for estimating solar radiation and the correlation coefficients in both methods are significant at 95% confidence level. Annual solar radiation zoning of Golestan province indicates the range of annual radiation varies from 1089 kW/m2/year in forested mountainous areas up to 1800 kW/m2/year in the southwestern heights where the average of total annual radiation is 1485 kW/m2/year. The region of maximum annual radiation is located in the southwestern heights of Golestan province. In this area, solar rays strike the ground more vertically than in the other parts of the province, and also it has a semi-arid and cold mountainous climate. Moreover, the northeastern region of Golestan province has suitable annual solar radiation (1500 to 1600 kW/m2) due to its semi-arid climate and the high annual sunshine hours. The overlap map of the received radiation of Golestan province with its topography shows the appropriate quality of zoning in this area. The results of this overlap map indicate that the annual solar radiation is minimum in forested and wet areas and is maximum in semi-arid and low rainfall areas of the province. Therefore, the northeastern and southwestern regions of Golestan province have a good potential for utilizing solar energy.