Heat and drought: Europe's electricity market also works thanks to photovoltaics

The extreme heat and drought gripping much of Europe have triggered concerns over the reliability of power generation, particularly affecting thermal and nuclear plants reliant on cooling water. However, experts warn that while localized disruptions are occurring, a widespread blackout is unlikely due to the flexibility of the energy market and the increasing role of solar power. According to reports from Germany’s n-tv and other media outlets, the situation has led to reduced output at several key facilities, including nuclear reactors in Hungary and Romania and coal-fired plants in France. The crisis began with record temperatures and low river levels, which have made it difficult for power stations to operate efficiently. In Hungary, the Paks Nuclear Power Plant, one of the country's largest electricity producers, has been operating at significantly reduced capacity because its intake of cooling water from the Danube River is unreliable. Similarly, the Cernavodă 1 reactor in Romania was forced to shut down temporarily for the same reason. In France, up to 3.65 gigawatts of nuclear output were unavailable during the height of the recent heatwave, according to Leonhard Gandhi of the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. Meanwhile, the limited flow of rivers has also impacted the transport of coal, a critical fuel for many German power plants. The inability to move sufficient coal via inland waterways has further strained supply chains, especially in regions where coal remains a major energy source. This has raised questions about the resilience of traditional fossil fuel-based power generation amid climate extremes. Despite these challenges, the expansion of photovoltaic installations across Europe has helped mitigate some of the strain on the grid. Solar farms are currently producing large amounts of electricity during daylight hours, which are being used to charge pumped-storage hydroelectric facilities in Switzerland, Austria, and Norway. These storage systems can then release stored energy during peak demand periods, helping to balance the grid even when solar output declines in the evening. However, this transition is not without its complications. In the evenings, when solar production drops off, there are occasional shortages because coal-fired plants are not being operated due to low prices. As a result, gas-powered generators must step in, often at higher costs. In Switzerland, researchers at the Federal Research Institute for Forests, Snow, and Landscape have noted that the shift in weather patterns is altering the dynamics between run-of-the-river hydropower and pumped-storage facilities. With lower reservoir levels, run-of-the-river plants are producing less, while pumped-storage units are benefiting from increased snow and glacier melt. While this combination helps offset some of the lost rainfall, it results in fewer peaks of generation than usual, with only one major spike in the evening instead of two or three. Gandhi emphasized that the current conditions highlight the growing importance of solar and battery storage systems in maintaining grid stability during heatwaves. Both technologies require little to no cooling water and are performing well under high temperatures. He also pointed out that future fusion-based nuclear power could offer additional advantages, as it would generate more waste heat per kilowatt-hour, potentially making it easier to manage in hot climates. As the summer progresses, the focus will remain on monitoring how these different energy sources interact and whether the current strategies can sustain the grid through prolonged dry spells. For now, the outlook suggests that while the situation is challenging, the diversification of the European energy mix is providing a buffer against widespread outages.