On the spatiotemporal variability and potential of complementarity of wind and solar resources

The anticipated greater penetration of the variable renewable energies wind and solar in the future energy mix could be facilitated by exploiting their complementarity, thereby improving the balance between energy supply and demand. Based on the hypothesis that a complementary use of wind and solar is possible, this investigation provides information about the spatiotemporal scales on which there is potential for the synergistic use of wind and solar in Germany. The results show that the wind-solar complementarity depends very much on the time scale under consideration. Regardless of the spatial scale, potential for complementarity is greatest on the seasonal scale, where the annual cycles of surface incoming solar radiation and surface wind speed show the strongest anti-correlation. On all other scales studied, including daily and inter-annual scales, the potential for wind-solar complementarity is significantly lower with wind and solar being usually very weakly anti-correlated or being uncorrelated. On these scales, there is hardly any compensation of times with low solar resource by the wind resource and vice versa. There is also hardly any solar-solar or wind-wind complementarity in different regions because their regional inter-regime dynamics are similar and do not show any significant differences. From the results, it is therefore concluded that there is little potential for the complementary use of wind and solar in Germany, except on the seasonal scale. Germany's low complementarity potential reinforces the need to systematically advance other options for mitigating the individual volatilities of wind and solar such as energy storage systems and transboundary exchange of renewable power in a pan-European electricity grid. Although the results are limited to a single country, the proposed novel data-driven approach can be readily transferred to study wind-solar complementarity in other parts of the world. It enables for the first time the consistent small-scale assessment of wind-solar complementarity in large, transnational areas and has the potential for being established as an essential tool to improve electrical grid operability.