Development of an Automated Ground Solar Radiation System for Enhancing Energy Supply in Zimbabwe

A gap in Zimbabwe’s energy supply and demand can be filled by extensive incorporation of solar energy in the country’s current energy mix. The amount of solar energy to be harvested at any site varies in quantity with time and location following variations in the received solar radiation. This research was conducted to develop an automated system which uses solar radiation equations, geospatial techniques and python programming to estimate received solar radiation in Zimbabwe. To validate the system performance a comparison between system results and ground measured radiation was conducted using statistical metrics such as Pearson correlation (<I>R</I>), Coefficient of Determination (<I>R2</I>), Root Mean Square Error (<I>RMSE</I>) and Normalised Mean Absolute Error (<I>NMAE</I>). Suitable sites for solar harvesting were determined using Multi-criteria Decision Making (MCDM) and weighted overlay analysis. The developed system determined temporal evolution in ground solar radiation from sunrise to sunset, and hours before 08:21am had radiation values below 0.9Mj. From 9:21am to 14:21pm radiation values were above 1.5Megajoules (Mj) with peak radiation of 2.13Mj at 12:21pm. The computed statistical metrics showed that there was a good agreement and better performance as most months had a Person correlation above 0.57, RMSE less than 2.7 and NMAE less than 1.7. The months of May, June and July were the peak of winter season evidenced by less radiation intensities between 14Mj and 18.5Mj whilst September to March had higher radiation ranging 20Mj to 26Mj. From the conducted site suitability analysis, 0.77% was highly suitable, 30.67% was suitable, and 5.1% moderately suitable and 63.45% falls under restricted areas. By consideration of only 1% of the highly suitable areas while using a solar system with 10% efficiency, 197.41 Gigajoules (GJ) can be harvested in Zimbabwe. Therefore, this sustainable energy can be used to supply Zimbabwe and bridge the current energy gap.