Temporally compounding energy droughts in European electricity systems with hydropower

As renewable energy capacities continue to grow (rapidly), the European electricity system will become vulnerable to extreme events in the form of energy droughts—periods of low production coinciding with high demand. In this work, we use a large model ensemble of 1600 years of daily climate data in conjunction with an energy production and demand modelling framework and consider present-day installed capacities to compute the full distribution of renewable electricity production and demand in the present-day climate. This approach enables us to examine in detail the specific events at the tail of the distribution that pose the highest risks to energy security.

In particular, this study focuses on energy droughts occurring once every ten years in six European countries: Sweden, Norway, Italy, Spain, France, and Switzerland, chosen because of their specific renewable energy mix including hydropower. We analyze energy drought events and their corresponding meteorological conditions and find that energy droughts result from processes that cause (temporally) compounding impacts in the energy and meteorological system. These processes can turn what might have been short-term droughts into prolonged, cumulative energy crises. For instance, low reservoir inflows in spring quadruple the chance of prolonged energy droughts: reduced snowpack and rainfall lower hydro-availability but also dry-out subsoils, increasing the chance of heatwaves and thereby extending the energy problems into summer.

We identify and evaluate three compounding energy/climate conditions and quantify the associated risks. These results can inform the energy modelling community where high-risk meteorological conditions can be applied in power system models to optimize and analyze the robustness of future energy system designs, and provide insights on the specific characteristics of the risks of multiyear energy droughts to policymakers and energy companies.