Solar Power Struggles as Heatwaves Reduce Efficiency

“I expect profits to be halved. Everyone thinks that solar power generation would work well during heatwaves, but it’s the complete opposite.”

Mr. A, who operates a solar power plant of approximately 1MW, megawatt scale in Chungcheongbuk-do, said on the 4th, “The recent consecutive heatwaves have actually resulted in power generation falling short of expectations,” and added, “This is the case.” As the equipment heated up under the intense sunlight, inverter overheating alarms went off one after another, and eventually about a third of the entire facility had to be shut down.

A midsummer day with clear skies and intense sunlight may seem like the best season for solar power generation at first glance. However, for solar power operators, heatwaves are not entirely welcome. While sunlight is the fuel for power generation, excessive heat actually reduces efficiency.

In reality, the nationwide solar power generation during the recent heatwave was lower than in spring. According to the Korea Power Exchange, on August 2, when most regions across the country experienced a heatwave, the maximum output reached only 26.89GW, gigawatt. In contrast, during the mild weather of last April, solar power generation peaked at 32.26GW on the 7th. It also recorded 30.84GW on May 8.

The reason lies in the characteristics of solar panels. While solar panels can generate more electricity with stronger sunlight, their efficiency drops when the panel temperature rises excessively. Typically, for every 1 degree Celsius increase above the standard panel temperature of 25 degrees Celsius, the maximum output decreases by approximately 0.4–0.5%. The temperature of panels exposed to intense sunlight can be over 20 degrees Celsius higher than the outside temperature. Assuming the panel temperature reaches around 60 degrees Celsius during a heatwave with a daytime temperature of 35 degrees Celsius, the output can drop by over 10% compared to when the temperature is 25 degrees Celsius, even with the same amount of sunlight.

The problem is that such heatwaves are recurring every year, making it difficult to view them merely as unusual weather phenomena. As solar power facilities are rapidly increasing, industry voices suggest that when evaluating the profitability of power generation projects, not only the amount of sunlight but also the degree of heat should be considered as separate variables.

The renewable energy cloud platform operated by the Korea Energy Agency calculates the expected power generation and economic feasibility of solar power based on factors such as solar irradiance, facility efficiency, and loss rates. However, it does not account for the extent to which panel temperatures rise due to external temperature increases and how much this reduces generation efficiency as separate calculation variables.

In response, meteorological authorities have begun examining the relationship between heatwaves and solar power efficiency. The Gwangju Regional Meteorological Administration has initiated a study to estimate how solar panel temperatures change during this year’s heatwave and analyze its impact on generation efficiency.

Experts analyze that as climate change leads to more frequent extreme weather like heatwaves, solar power facilities must also adapt. Kim Sook, Secretary-General of the Solar Power Generation Association, said, “If heatwaves with high temperatures ranging from the late 30s to nearly 40 degrees Celsius, as seen recently, continue to recur, solar modules will need to respond technically in line with these changes.”