Assessing the impact of a solar eclipse on weather and photovoltaic production

With the strong expansion of the installed renewable energy over the last years, the relevance of weather forecasts for operating the German power system has considerably increased. In that context, rare but important events like the solar eclipse on the morning of 20 March 2015 pose an additional challenge when operating the power system, as it affects the photovoltaic (PV) power production by inducing strong gradients in the feed-in. In order to maintain grid stability, the uncertainties associated with the eclipse have been estimated in advance for planning necessary precautions. Especially the maximum gradients in PV-power were of importance for the provision of balancing energy. Numerical weather prediction (NWP) is very suited for this assessment, as it allows to consider the complex mechanisms occurring in the atmosphere. Thus the impact of the eclipse on meteorological parameters which affect the PV-power generation were evaluated. Sensitivity studies with NWP models have been conducted in order to assess the reduction in short wave radiation and temperature during the total solar eclipse months before the actual event. For this purpose, model simulations with the non-hydrostatic COSMO models from the German Weather Service (DWD) have been performed over Germany and Europe. As the weather situation and especially the cloud cover during the eclipse could not be known in advance, a realistic worst case (clear sky conditions) and a best case (overcast conditions) scenario were simulated over Germany. Thereof the PV-power production has been estimated and analyzed for the different scenarios. The NWP model data from the sensitivity studies are openly distributed (doi:10.1594/PANGAEA.839163). As near real-time NWP simulations considering the solar eclipse were conducted a few days prior to the event, they are herein validated with measurements. Furthermore, the actual PV-power production and actions taken by the TSOs during the solar eclipse are stated.