Solar Eclipse: A Stress Test for Renewable Energy

The solar eclipse on September 12 is not only a fascinating astronomical event – it also provides a remarkable real-world example of how closely weather, the atmosphere, and renewable energy are interconnected.

Solar eclipses: a challenge for solar energy

The most significant impacts in Europe will be seen in Portugal, Spain, and Iceland, where a total solar eclipse will occur in the evening. There, the temporary reduction in solar irradiance will lead to a noticeable drop in photovoltaic (PV) power generation, followed by a moderate recovery. These power ramps need to be carefully anticipated by grid operators and energy traders.

Little impact on PV generation in Germany

Since there will only be a partial solar eclipse in Germany and the sun will already be lower in the sky by evening, no significant impact on PV generation is expected here.

Wind power can also be affected

Less obvious than with solar energy is the potential impact on wind energy. During a solar eclipse, the atmospheric boundary layer changes: solar heating decreases, turbulence weakens, and the vertical wind transport can temporarily diminish. Whether this results in lower wind power generation depends largely on the prevailing weather conditions.

Accurate forecasts for exceptional situations

By combining numerical weather prediction models, satellite data, irradiance forecasts, and real-time measurements, modern nowcasting systems provide a reliable assessment of even exceptional situations such as a solar eclipse. This enables energy traders, aggregators, and grid operators to make informed decisions well in advance – because a stable energy system starts with an accurate forecast.