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Best of Both Worlds: Agrivoltaics Boosts Yields of Crops and Solar While Saving Water

published: 2019-09-06 0:00

Credit: Peggy Choucair from Pixabay

Not one, but two research teams from the U.S. found that agrivoltaics is a win-win for the crops and the solar modules. According to one of the studies from Oregon State University, agrivoltaics thrive in environments such as cropland, grasslands, and wetlands. The other study from the University of Arizona has gone even further and proved that Agrivoltaics can also flourish in dryland.

While solar power plants are nice and clean without keeping the residents near them up at night, worrying about a meltdown could take everything away from them. Politicians and farmers, on the other hand, do not always welcome the solar power plants that seem to be ever-expanding. The solar power plants can take up so much land, that some may feel that the agricultural lands are being displaced by arrays after arrays of the solar energy.

However, solar power and agriculture do not need to be a zero-sum game. Agrivoltaics, also known as solar sharing, may be the key to unlock the potential dual-use for the land. According to Oregon State University’s high-profile study published in Nature, it is possible that land competition or other geographical limitations could be countered by agrivoltaics, while the crop yield can benefit from solar sharing.

The research team behind the study has found out that solar power performance would be most efficient, provided that its surroundings are highly insolated, slightly humid, with light winds and at a moderate temperature, such as cropland, grasslands, and wetlands. “The vegetation has been shown to be most efficient at using available water under mesic conditions where atmospheric evaporative demand is balanced by precipitation supply.” wrote the researchers. 

Furthermore, it should not come as a surprise that both solar power and crops need a similar climate to thrive. The success of agriculture also heavily relies on the amassing of the light and heat from the sun. Consequently, a lot of areas suitable for solar energy have already been obtained for agricultural use.

A Win-Win-Win Interdependence
The Oregon team has established that PV installations are not the only beneficiary under this arrangement. Having semi-transparent PV modules hovering above the vegetation does not hinder its growth. The yield of some vegetables is even improved. “Some varieties of lettuce produce greater yields in shade than under full sunlight; other varieties produce essentially the same yield under an open sky and under PV panels.” stated the study.

Confirming the study done by Oregon State University, a research team, from the University of Arizona has taken things even further, and their findings are incredible. According to their paper published in Nature Sustainability, not only that the solar panels do not curtail the crop growth, the vegetable and fruit production has been doubled, even tripled, with the panels shielding them from excessive direct sunlight and preventing transpirational water loss by 65%, which saves precious water resources.

The Arizona team, led by Greg Barron-Gafford, the lead author on the paper and an associate professor in the School of Geography and Development, created a designated spot for agrivoltaic research and planted chiltepin pepper, jalapeno, and cherry tomato plants under a photovoltaic installation. To monitor the growth of the crops and the solar array performance, the researchers regularly observed and measured the exposure of incoming sunlight, air temperature, and humidity.

Their findings show that agrivoltaics has significant impacts on three important factors determining the growth of the crops: air temperatures, the exposure of direct sunlight and water. PV modules provide adequate shading for the crops, which can maintain a milder, more stable climate for the crops to flourish than the conventional planting practice, which exposed them to direct sunlight. A lower vapor pressure deficit is also observed in the agrivoltaics system, which means the air is more humid and creates a more nurturing environment for the crops.

"At the same time, we found that each irrigation event can support crop growth for days, not just hours, as in current agriculture practices. This finding suggests we could reduce our water use but still maintain levels of food production," explained Greg Barron-Gafford, emphasizing that the soil moisture in the agrivoltaics system is constantly approximately 15% higher than the control group, when the irrigation events take place only every other day, simulating drier seasons.

Agrivoltaics is not only advantageous to the crops, but also quite beneficial to the solar modules, which are sensitive to a high temperature by nature. When they are heating up, their yields are declining. Having a plantation underneath the heat-sensitive solar panels can help them cool down.

"Those overheating solar panels are actually cooled down by the fact that the crops underneath are emitting water through their natural process of transpiration – just like misters on the patio of your favorite restaurant." The team leader then hammered the point home: "All told, that is a win-win-win in terms of bettering our how we grow our food, utilize our precious water resources, and produce renewable energy.”

Great News for Land-Scarce Countries
The findings from the Oregon and Arizona teams could be very beneficial to countries such as the Netherlands, which is not blessed with expansive lands like the U.S. There has already been voiced concerns regarding losing agricultural lands to the solar parks.

Vattenfall, a Swedish company, is interested in testing agrivoltaics in the Netherlands. According to Margit Deimel, Vattenfall’s director of large-scale solar, the company intends to increase the acceptance of solar parks by co-locating the energy and crops. However, the choice of crops is limited to the ones that do not grow too tall at the moment, such as cabbages, onions, potatoes or soft fruits.


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