Farmers are combining green energy and agriculture, and it looks like a win-win for all stakeholders.
But the sprawling solar panels being installed over crops have effects that no one predicted. They function like umbrellas, trapping moisture and changing rainfall patterns.
Now, storms are being inadvertently redirected to form heavy barriers above the soil. These sheets of water are coming down like curtains.
What is it about the solar farm that generates the ‘rain curtain’ phenomenon?
How agrivoltaics is changing the climate in unpredictable ways
The agrivoltaics industry is booming. So far, pairing food with clean electricity generation looks positive at ground level.
Land use is optimized, renewable energy is generated, crops are protected, and water is conserved. Panels function more efficiently in the microclimate, and farmers benefit from diversified income streams.
But what if we look up? The presence of thousands of solar panels in a confined area was bound to have an impact on the microclimate.
And now we know that’s true.
Researchers set up an experiment across a huge plot in Montpellier, France. The plot covers roughly 5,270 square feet of land, more than enough to track larger-scale effects.
Four rows of panels are installed at an elevated 16.4 feet in the air. Each is 6.5 feet long by 3.3 feet wide. Naturally, their architectural bulk makes them act like giant umbrellas. The result is a notable redistribution of water.
Three distinct zones started to emerge on the ground. Sheltered spaces remained dry, and gaps between the rows received the normal rainfall.
But border zones saw the overhead panels reacting with force.
The data turned dramatic and it looked like a crop catastrophe
By intercepting rainfall and channeling it into vertical streams, they effectively created barriers of water.
For scientists, it was mathematical chaos. The channeling of water resulted in very messy data.
Irrigation specialists measure water distribution with the coefficient of variation metric. An ideal score is close to zero.
Researchers saw the score plummet when the panels were held flat during a storm. Spatial variation skyrocketed to 2.13. For perspective, any farmer would consider this catastrophic. It means some crops drown while others starve.
Dynamic agrivoltaics, where the panels frequently change angle by being rotated on motorized jacks, makes the variables more complex.
The tilting panels combined with shifting winds make the runoff discharge violently across the field. The water becomes a moving wall capable of slicing across the relatively fragile crops.
Smart software to the rescue: Agrivoltaics is saved
Engineers turned to smart software for a solution, building a rain redistribution model called AVRain and pairing it with Hydrus-2D soil tracking.
Algorithms force the panels to react to wind speed, wind direction, and heavy downpours in real-time. It worked brilliantly based on an ‘avoidance strategy.’
The scary variation score dropped from 2.13 to a uniform 0.22.
The trick was mastering the ‘rain curtains’ with science and technology
Rain curtains are dense, concentrated vertical sheets of water. They form when the 6.5-foot-wide solid surface of a panel funnels all that collected rainwater to its edge.
Then, it drops the load from a height of 16.4 feet. Combined with the wind, these discharges create literal curtains of falling water that have a slicing effect in the air.
By steering these water formations, farmers can finally stop soil erosion and protect their crops.
It also means that a structural threat can become a guided irrigation tool. The runoff can be directed to where it’s needed or even stored for drier times.
It makes you wonder what other climate solutions are hiding inside a situation that looks like chaos. What other agrivoltaic leaps in technology are waiting just around the corner?
The full study is available here: Elamri, Y., Cheviron, B., Mange, A., Dejean, C., Liron, F., and Belaud, G.: Rain concentration and sheltering effect of solar panels on cultivated plots, Hydrol. Earth Syst. Sci., 22, 1285–1298, https://doi.org/10.5194/hess-22-1285-2018, 2018