WHY HIGH TEMPERATURES CAN REDUCE SOLAR PANEL PERFORMANCE

Although sunlight is widely considered the best friend of solar panels, extreme heat can actually reduce their efficiency and power output, according to Engadget.

Solar panel manufacturers test and rate their products under standardized conditions, typically with cell temperatures of 25 degrees Celsius and solar irradiance of 1,000 watts per square metre. However, real-world conditions can be significantly different, particularly during hot summer days.

COLDER WEATHER CAN IMPROVE EFFICIENCY

Solar panels technically become more efficient in colder weather because their electrical voltage decreases as temperature rises. However, this does not necessarily mean that cold days produce more electricity overall.

Hot summer days often provide considerably more hours of strong sunlight, meaning that total electricity production can still be higher during warmer periods despite reduced panel efficiency.

The key issue is that the temperature reported in a weather forecast does not necessarily reflect the actual temperature of a solar panel installed on a rooftop, the Nezavisne novine reported.

HOW HOT CAN SOLAR PANELS GET?

Sandia National Laboratories, part of the U.S. Department of Energy, models solar module temperatures by taking several factors into account, including outdoor air temperature, solar irradiance, wind speed and the way the panels are mounted.

Once solar cells heat up above the reference temperature of 25 degrees Celsius, their power output begins to decline according to the panel's temperature coefficient.

For example, REC Group reports a power reduction of around 0.24 percent for every degree Celsius increase above the reference temperature for its Alpha Pure-RX model. Qcells, meanwhile, reports a reduction of approximately 0.29 percent per degree Celsius for its Q.TRON BLK M-G2+ series.

This temperature coefficient can therefore be an important consideration for consumers choosing solar panels, particularly in regions with very hot summers.

25 DEGREES CELSIUS IS NOT THE MAXIMUM OPERATING TEMPERATURE

Importantly, the 25-degree Celsius reference point does not represent the maximum temperature a solar panel can withstand.

According to Qcells, its Q.TRON panels can safely operate at temperatures of up to 70 degrees Celsius. REC Group states that its Alpha Pure-RX module can withstand temperatures of up to 80 degrees Celsius.

However, extremely high temperatures can still have long-term consequences. The U.S. Department of Energy warns that excessive heat can permanently damage solar cells and other materials within a module, potentially shortening the panel's operating lifespan.

THERE IS NO UNIVERSALLY PERFECT TIME FOR SOLAR POWER

The relationship between temperature and solar power production is therefore more complicated than simply choosing between hot and cold weather.

Cloud cover, snow, roof orientation, panel angle and the position of the Sun can have a major impact on how much electricity a solar system produces.

As a result, the daily production peak does not necessarily occur between 10 a.m. and 4 p.m., while the summer months are not automatically the most productive period for every solar installation.

WHY SYSTEM DESIGN MATTERS

To prepare for periods when weather conditions are less than ideal, some homeowners follow a so-called 20 percent rule, designing solar systems with more capacity than their estimated electricity needs.

This additional capacity can help compensate for periods of reduced sunlight, high temperatures and other unfavorable conditions.

For more precise estimates, homeowners can use the free online PVWatts Calculator, developed by the U.S. National Renewable Energy Laboratory. The tool allows users to enter their location and estimate monthly and annual electricity production based on long-term meteorological data.

The calculations demonstrate an important point: there is no single ideal month or time of day for solar energy production. The actual performance of a solar system depends on a combination of temperature, sunlight, weather, location, orientation and system design.