There is a new, budding romance on the Energy Transition horizon – one between photovoltaics (solar panels) and agriculture (both crops and livestock). It’s further along in some other countries than in the U.S. – some foreign “Agri-voltaic” couples appear to be well on their way to a long-term commitment that could soon bear abundant fruit – as it were.
In fact, as in some of the best relationships we know, the pairing of solar panels and farming can be mutually beneficial, sometimes allowing them to “be their best selves” and to produce more together than they could separately.
Agriculture is estimated to be responsible for roughly 30% of the world’s greenhouse gas emissions, so finding ways of reducing its energy and water consumption would be helpful for our future. Evidence is mounting that growing certain crops in the partial shade of photovoltaic panels can result in equal or enhanced crop yields, increase the efficiency of the solar panels, and reduce the watering needs of the crops.
A key element in the potential success of agrivoltaics is the fact that too much sun can be a bad thing for many crops, especially in sunny places like the Southwest. Once the solar intensity reaches a certain level, photosynthesis actually decreases or even shuts down – plants respire water to keep from overheating. The right amount of shading, which varies by crop, can optimize crop yield.
A 2022 study of the various responses of different crops to shading by PVs found that berries, fruits, and fruity vegetables benefited the most from certain amounts of shading. A 2019 study found that in a very sunny region tomatoes and peppers have increased yields when grown in the shade of PVs.
Indeed, a 10-acre raspberry farming experiment in the Netherlands has shown that plants grown under PVs have berries of equal or better quality and yield than those in a conventional field. While the berries grown conventionally were damaged by hail, those under the panels were protected from all types of weather damage and required up to 50% less water. Meanwhile, the PVs operated more efficiently due to cooling, although less productively due to suboptimal solar orientation.
University researchers in South Korea have found that broccoli grown under 8-foot high panels set at a 30-degree tilt was of equal quality and taste as conventionally farmed broccoli and that it was a deeper green color.
“Solar grazing” is a brilliant example of synergistic solar/animal farming. Pasture lands are planted in solar panels high enough for sheep to wander among and be sheltered from excessive sun or precipitation. The landowner profits from generating power, and the solar provider has reduced maintenance costs. And with the regenerative agriculture technique of rotational grazing, the soil will increase in fertility, store more carbon and retain more water. Apparently solar grazing really only works with sheep, though, and not other livestock, due to various factors.
Japan began deploying agrivoltaics back in 2004. Inspired by a need for renewable energy sources due to scaling down their nuclear power, along with a problem of increasingly abandoned farmland, they offered regulatory incentives to couple solar energy and farming in a profitable way. The result was a 76% increase in Japan’s solar-generated electricity from 2012 to 2019 and a current total of 2,000 agrivoltaic farms.
Right here in Rockport, Maine, there has been a 5-acre wild blueberry agrivoltaics experiment underway since 2017. At this point, the results are inconclusive, due to uncertainty about whether a reduced yield has been due to the disruption from the panel installation or from the shade. However, the farmer is reportedly hopeful that the plants may produce better as they adapt to the conditions.
Our research revealed that there are crops for which agri-Voltaics are not suited – corn is one. In France, however, a large-scale experimental project is growing soybeans under 5,500 solar panels that track the sun and tilt to allow rain and shelter from hail, all while producing 2.5 MW peak power.
The soybean experiment is of considerable interest because of the huge amount of land currently used for soybeans. They are a very close second to corn with over 80 million acres in the US alone (300 million worldwide). If we speculate a bit and suppose that with 10% coverage of those fields by properly spaced PVs the soybean yield could be the same and water usage decreased, there is potential for 8 million acres of PVs in the soybean growing areas of this country. The electrical energy yield – around 7,000 TWh per year – would be enough to supply all of the electricity the U.S. uses today plus enough to electrify 90% of our transportation and all of our residential energy usage.
What no one has published prominently enough for us to find is a quantification of how much more is produced – crops and energy, that is – with these agrivoltaic symbioses than would be produced on the same piece of land that was simply divided between PVs and crops. A lot of research is underway, and there must be good enough data to generate this effort, but the jury seems to still be out.
So for now, we won’t count on a lot of weddings, but we’ll certainly “root” for any farmer-solar couples we meet… .
Paul Stancioff, PhD., is a professor emeritus of physics at UMF. Cynthia Stancioff is a re-writer of her own and others’ prose. Email: pauls@maine.edu or cynthia.hoeh@gmail.com Previous columns can be found at https://paulandcynthiaenergymatters.blogspot.com/.
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