Hitze und Stromversorgung – Keine Stromlücke in der Schweiz dank Sonnenstrom

Swiss power producers have avoided a supply shortage this summer despite record low river levels and two offline nuclear reactors, according to utility reports and regulatory statements. The gap left by reduced hydropower output has been filled primarily by solar energy generation. Weeks of dry weather with little rainfall have caused small rivers to shrink to trickles, while major waterways including the Aare, Rhine, and Rhône are carrying some of the lowest volumes recorded since monitoring began. This prolonged drought has significantly impacted electricity production from run-of-river hydroelectric plants along these rivers. Current output levels are markedly lower than long-term averages, a trend visible even when compared against other exceptionally dry years such as 2003 or 2022. The contrast is particularly sharp when measured against wet years like 2016. Energy companies have quantified their losses due to insufficient water inflow. Repower, a utility based in the canton of Graubünden, stated that its hydroelectric plant production from May through July fell approximately 25 percent below the long-term average. Similar conditions affected Forces Motrices Valaisannes, a Valais-based energy firm. The company noted that low winter precipitation resulted in a thin snowpack at the end of the season, which was below historical norms. Consequently, snowmelt was reduced, leading to decreased power generation from its run-of-river facilities during the same three-month period. These effects extend beyond the Alpine region. Alpiq, an energy group headquartered in Lausanne, reported very low water inflows for its run-of-river plants, specifically those located along the Aare River. The company calculated a decline of roughly 15 percent relative to long-term averages for these installations. Despite the drop in hydroelectric output and the temporary shutdown of both Beznau I and Beznau II nuclear power plants, Switzerland has not yet faced an electricity bottleneck. Axpo, the operator of the Beznau reactors, clarified that the units were taken offline not because of low water volume, but due to high water temperatures. The plants use river water for cooling, and regulations prohibit discharging water above specific temperature thresholds to protect aquatic life. Because the Aare River is currently very warm, Axpo could not release additional heated water into the stream. The primary factor preventing a supply crisis is the substantial contribution from solar power. Unlike previous summers, photovoltaic systems have generated a significant portion of the national electricity mix this year. This shift is attributed largely to the massive expansion of solar capacity installed since the outbreak of the war in Ukraine. With the sun shining daily from early morning until late evening, solar farms have produced large amounts of clean energy. The Federal Electricity Commission, known as Elcom, which oversees supply security in Switzerland, confirmed that solar energy is acting as a crucial buffer against unfavorable hydrological conditions. The commission stated that without the strong growth in photovoltaics over recent years, the current electricity balance would be more strained. It added that absent this additional solar input, Switzerland would likely need to import more water from neighboring countries to maintain grid stability. The situation highlights how climate variability interacts with infrastructure changes. While traditional hydropower faces challenges from drought, renewable alternatives are stepping in to fill the void. Utilities continue to monitor river levels and temperatures closely. The interplay between thermal constraints on nuclear cooling and the variable nature of solar generation requires careful management. However, the current data suggests that the expanded solar fleet is effectively compensating for the deficits in other sectors of the power mix. No blackouts or emergency measures have been reported. The focus now shifts to maintaining this balance as the summer progresses. Regulatory bodies will continue to assess the impact of weather patterns on the grid. Utility operators remain vigilant regarding potential further drops in river flow. The successful integration of solar power into the critical peak hours demonstrates the resilience of the modernized Swiss grid. Future planning will likely emphasize further diversification of energy sources to mitigate similar risks associated with extreme weather events. The current experience serves as a practical test case for the reliability of solar energy during periods of stress on conventional hydropower resources.