Using satellite data for assessing spatiotemporal variability and complementarity of solar resources - a case study from Germany (vol 30, pg 515, 2022)

The integration of solar energy into Germany's energy mix has multiplied over the last two decades. Therefore, it becomes increasingly important to quantify the spatiotemporal variations of solar energy to efficientl promote photovoltaic systems' spatial spreading and strengthen the stability of power grids. Only comprehensive information on surface incoming solar radiation's long-term small-scale variability can provide the desired decision support. Clouds, and to some extent aerosols, are essentially responsible for the observed changes in solar energy penetrating the atmosphere. Germany was used as an example in this work, where solar energy currently accounts for around 8 % of annual electricity generation. The daily values of a 25 year dataset (1991-2015) available from satellite measurements were analyzed, depicting the long-term, large-scale evolution of the surface incoming solar radiation and cloud dynamics on a small spatial scale (0.05 degrees x 0.05 degrees). The most signif cant long-term increase in solar radiation was observed in spring, mainly inf uenced by the seasonal changes in cloud cover. The pronounced annual cycle of solar input reinforces the need for storage systems to transfer the harvested solar energy to periods with minor solar input. Moreover, there is hardly any solar-solar complementarity in different regions because their inter-regime dynamics are similar and do not show any signif cant differences. The proposed methods for assessing complementarity show explicitly the areas where the solar potential is not yet fully exploited, and additional PV capacities should be built. From these results, it can be concluded that there is further potential for the complementary use of solar energy in Germany on the national level.