It’s an ironic fact that sun-harvesting solar panels function better when they’re not too hot. But luckily researchers have now discovered precisely how to cool them down. Building solar panels at a specific height above crops can reduce surface temperatures by up to 10 °C, compared to traditional panels constructed over bare ground, they’ve found.
The results, published in the journal Applied Energy, are the latest contribution to a growing body of research on agrivoltaics: a farming method that aims to maximize land use by pairing solar panels with cropland, thus minimizing competition between energy production and food. We already know that agrivoltaics can increase land-use efficiency, produce plenty of electricity on minimal land, and may also improve crop yields by shielding plants from heat and wind.
But how to maximize this relationship for the hard-working solar panels is something that we knew less about—until this research.
Using a one-of-a-kind model, researchers on the new study simulated the effects of varying ground cover levels, different amounts of evapotranspiration from the vegetation, and various panel heights combined to affect the hyperlocal microclimate. Using these factors their model worked through 18 different scenarios, which also simulated different wind speeds and ambient air temperatures.
From this, it spat out a very precise recommendation for the Ontario-based agrivoltaics farm that the researchers used as their test case.
Hovering solar panels over an area vegetated with soybeans would reduce panel temperatures by 10 °C compared to traditional solar farms built over bare ground. Mainly, this was due to the light-reflecting powers of the soybeans (70%, versus just 20% from bare ground), which cooled the ground surface and by default reduced the panels’ exposure to heat. But the exact panel height was important too: the model revealed that constructing solar panels on legs that stood 4 meters above the crops created the optimal conditions for convective cooling to occur between the ground and the units. Evapotranspiring vegetation also provided cooling as water droplets formed at the base of the panels.
Previous research shows that panels experience decreasing efficiency of 0.5% per every degree rise beyond 25 °C, the researchers say. So, this passive cooling through vegetation will increase their overall production and longevity. What’s more, this could even lead to larger economic benefits down the line, their model suggests.
Such findings could be helpful for tackling prevailing resistance to agrivoltaics, which often revolves around the worry that the panels will undermine crop yields, or the crops will stop the solar panes from working as well. Proving that the combination can actually improve efficiency could help change minds, which may be helpful at brining people on side especially since solar panels can often be more expensive to set up on farms.
The researchers think this is needed, as agrivoltaics are set to become an increasingly valuable method of growing more food, for more people, on our planet’s increasingly limited land. Taking the state of New York as an example, they note that 84% of land deemed suitable for solar development there is already farmland.
Crops and renewables will both need support to function in a changing world; this study suggests that each could in fact be instrumental to the other’s success.
Williams et. al. “The potential for agrivoltaics to enhance solar farm cooling.” Applied Energy. 2023.
Image: NREL via Flickr