“Agrivoltaics” Allows Food Growth and Solar Energy Production on the Same Piece of Land

Rural America has been a magnet for solar energy companies for the same reasons that farmers seek out the wide open spaces. The mostly flat, well-draining soils and unobstructed sunshine that make the US an agricultural powerhouse are also ideal for large installations of solar panels. This has raised much debate and concern about solar farms taking farmland out of food production. Some think a different approach to solar energy called “agrivoltaics” – in which growing crops and collecting the sun’s rays work in tandem – could be a viable solution to the polarizing issue.

Agrivoltaic farming integrates solar photovoltaic (PV) projects into active agricultural activity so the same land can used for both. Essentially, solar panels are place in fields and crops are grown beneath them. “It essentially mimics what humans have been doing for hundreds of years with agroforestry – think shade-grown coffee – intentionally creating partial shade to create multiple layers of agricultural productivity on the same piece of land,” says Jordan Macknick, lead energy-water-land analyst at the US National Renewable Energy Laboratory (NREL).

There are various types of agrivoltaic approaches, depending on the local climate, type of land, and crops being grown. Elevated PV panels, for instance, can be used with larger crops such as fruit trees and vineyards, while ground-mounted large-scale PV arrays can be coupled with low-height crops like leafy greens or even livestock.  

“As agrivoltaics involve strategic shading of the ground, it can often make the most sense in areas where you have an excess of sunlight and not enough water – in the US south-west, for example,” says Macknick. “We have particularly noticed improvements in agrivoltaic settings for peppers and tomatoes in the US south-west, and for leafy greens everywhere.” One study in Arizona found that the production of cherry tomatoes doubled and chiltepin peppers tripled under solar panels.

Solar shading can help protect crops from adverse weather effects while also reducing “evapotranspiration,” the combination of two separate processes whereby water is lost from the soil surface by evaporation and from the crop by transpiration. Water savings via solar shading are estimated as high as 14-29%. Proponents say this can not only prevent desertification, but can even help revegetate desertified land. Additionally, what evaporation does occur underneath the panels has the added benefit of cooling the PVs and boosting their electricity production.

Another harsh growing environment in which proponents say agrivoltaics can excel is rooftop farms, where limited water and higher temperatures can hinder both the functioning of panels and the growth of crops. Solar panels can start to lose efficiency when temperatures get above a mere 77 degrees, which happens quickly on rooftops. But the evaporative effect from the plants act as a built-in cooler while the panels protect the plants from the harsh rays of the sun. Recent experiments show that rooftop agrivoltaics could also extend the growing season of some crops by keeping them warmer at night.  

Agrivoltaics is still in its infancy, although advanced systems have been in development across the US, Europe, and many parts of East Asia for the last 15 years. Ranging from research projects to commercial operations, these systems recently reached the same solar capacity as the entire UK, climbing from only 5 to 14,000 megawatts between 2012 and 2021. Researchers are also experimenting with novel technologies such as semi-transparent solar panels, vertical photovoltaic “fences” (grow lights mounted on the underside of traditional panels) to improve the yield of agrivoltaic systems in light-starved environments.
 
As for the costs, agrivoltaic systems are significantly more expensive to install due to the larger and more complex mounting requirements. Since agrivoltaics are raised higher above the ground than conventional solar panels, the visual appeal may also be a hard sell to those that already consider traditional solar arrays a blight on the landscape.

If you’d like to learn more, NREL’s main research project on agrivoltaics is called Innovative Solar Practices Integrated with Rural Economies and Ecosystems (InSPIRE). The InSPIRE project developed a financial calculator to quantify the benefits of the practice, which is available HERE. It also developed a list of best practices for those interested in entering the field, which is HERE. Additionally, InSPIRE tracks all the active agrivoltaics site across the U.S., which can be found HERE. (Sources: NREL, Dezeen, CleanTechnica)