# Solar Potential in Saudi Arabia for Flat-Plate Surfaces of Varying Tilt Tracking the Sun
## 6 Conclusions  
The present study investigated the solar potential across Saudi Arabia on flat-plate solar panels that vary their tilt angle in order to receive solar radiation normally to their surfaces during the day. The main objective was to find the annual energy available in this configuration type under all-sky conditions. This was achieved by calculating the annual energy sum on flat-plate surfaces with varying tilt angles that track the sun across Saudi Arabia; the solar availability on a horizontal plane was also included for reference purposes. For this reason, hourly solar radiation data in the period 2005-2016 were downloaded from the PV-GIS platform for 82 sites in the country. The calculations for the energy received on the tilted surfaces were performed for a ground albedo equal to 0.2 (as a reference value) and also for a near-real ground albedo. The latter values were retrieved from the Giovanni website. The main result of the work was that the annual solar energy received by such (dynamic) mode (iii) systems varied between 2267 and 4319 \(\mathrm{kWhm^{-2}year^{-1}}\) within Saudi Arabia. Along with the annual energy sums, monthly solar energy values averaged over all locations and over the mentioned period were estimated under all-sky conditions. A regression equation was provided as best-fit curve to the monthly mean energy sums that estimates the solar energy potential at any location in Saudi Arabia with great accuracy (R\({}^{2}\) = 0.96). This expression may prove very useful to architects, civil engineers, solar energy engineers, and solar energy system investors in order to assess the solar energy availability in Saudi Arabia for sun-tracking flat-plate solar systems throughout the year. Seasonal solar energy sums were also calculated. They were averaged over all sites and over the period 2005-2016 under all-sky conditions. A new regression curve that best fits the mean values was estimated with absolute accuracy (R\({}^{2}\) = 1). Maximum sums were found in the summer (882 \(\mathrm{kWm^{-2}}\)), and minimum ones in the winter (667 \(\mathrm{kWm^{-2}}\)), as expected. Although unified curves were presented for the monthly and seasonal solar energy yields in all territory of Saudi Arabia numerically expressed in Table 3, individual monthly and seasonal curves for all 82 sites were given in Figures 6 and 8, respectively, in order for the interested scientist or engineer to see the individual solar energy yield variation. The correction factor, CF, introduced in [1], was also used in this work. A graph of CF as function of \(\rho_{\mathrm{r}}\) showed a linear dependence with increasing CF values as \(\rho_{\mathrm{r}}\) increased. Such a behaviour was claimed to be considered universal (i.e., representable as nomogram). Nevertheless, this universality remains to be confirmed at other locations in the world with different climate and terrain characteristics. Two more plots were also prepared: (i) a graph of CF vs. \(\mathrm{R\Delta H_{g}}\), and (ii) a graph of \(\rho_{\mathrm{r}}\) as function of \(\mathrm{R\Delta H_{g}}\). In both cases, 58 of the 82 sites were found to be accommodated within the \(\pm 1\sigma\) band around the mean \(\mathrm{R\Delta H_{g}}\) value of 5.57. The other 24 sites remained outside the band, thus indicating a loose dependence of CF (\(\rho_{\mathrm{r}}\)) on \(\mathrm{R\Delta H_{g}}\). These two graphs may be used as criteria for a strong (weak) dependence of CF (\(\rho_{\mathrm{r}}\)) on the received solar energy, but this conclusion remains to be confirmed at other sites worldwide with different climate and terrain characteristics. Conceptualization, methodology, data collection, data analysis, writing--original draft preparation, H.D.K. ; data collection, data analysis, writing--review and editing, A.F. ; writing--review and editing, M.A. ; writing--review and editing, E.R. All authors have read and agreed to the published version of the manuscript.