(Image courtesy of the National Renewable Energy Laboratory (NREL).)

In 2013, Oregon State University (OSU) Professor Chad Higgins took his “thinking walk” around campus and noticed that the pasture under the recently installed solar array was greener than the pasture receiving full sun. The observation planted a mental seed and he began to wonder about the relationship between renewable energy, sunlight, shade and crops. His degrees in agricultural, biological, mechanical and environmental engineering gave him not only a broad perspective but also the tools he needed to do more than simply muse on the topic. So he rolled up his sleeves, dug into the research, and cultivated his own plot in the burgeoning field of agrivoltaics (sometimes called agrophotovoltaics)—the symbiotic relationship where food crops and solar panels help each other’s performance. A recent paper on the topic, which Higgins co-authored with OSU Professor Ganti Murthy and PhD student Kyle Proctor, showed that adding photovoltaic arrays to just one percent of US farmland could generate enough electricity to meet 20 percent of the country’s electricity needs with minimal impact on crop yield. The researchers also demonstrated that the combination of food farms and solar farms supports the goals of the Green New Deal and offers long-term environmental and economic benefits. The paper was published in the open-access journal Sustainability.

Professor Chad Higgins. (Image courtesy of OSU.)

A Symbiotic Relationship

While all plants need sunlight for photosynthesis, some plants prefer shady locations. Even those that thrive in full sun, however, reach a “light saturation point” beyond which additional sunlight doesn’t cause more photosynthesis or plant growth. In fact, too much sunlight increases the plant’s need for water. Strategically placed photovoltaic panels, especially bifacial panels, which don’t have reflective backing, can let the right amount of sunlight reach the crops and prevent them from reaching the light saturation point. As a result, the plants stay healthy, farmers don’t need to irrigate as much and we get clean electricity.

Agrivoltaics: a symbiotic relationship. (Image courtesy of OSU.)

But wait—a truly symbiotic relationship means each helps the other, so what do solar panels get out of the deal? It turns out that with a traditional solar farm, the ground underneath the PV panels is often covered in gravel, which tends to get quite hot. Put crops underneath the panels, however, and the vegetation cools the area, and cooler solar panels operate more efficiently. In the aforementioned study, PV panels mounted above crops produced ten percent more electricity than their counterparts mounted over gravel.

In short, the panels help the crops grow and the crops help the panels perform. Symbiosis!

Pollinators

More than one-third of all cultivated crops require help from pollinating insects, whose natural habitats are rapidly declining with urban and suburban sprawl. Professor Higgins and colleagues conducted research on the effects of PV panels on flowering plants and pollinating insects in wildflower fields. Their paper, published in the journal Scientific Reports, showed that pollinators were just as attracted to partially-shaded fields as they were to full-sun fields. The partial shade also increased the number of nectar-producing flowers on the plants, providing even more food for pollinators, and delayed the timing of the blooms, making more food available to pollinators in the hot, dry late season when other sources of nectar are dwindling. When located in the vicinity of farms, the PV-covered wildflower fields provide food to keep the population of beneficial insects healthy, and these insects return the favor by pollinating nearby crops.

Native vegetation to attract pollinators. (Image courtesy of NREL.)

Economic Benefits

According to Higgins’ study, agrivoltaics can boost the economy in often-neglected rural communities. His proposed plan would create 117,000 new jobs in these communities, and these are just the jobs related to photovoltaics—there’s also the potential to increase agricultural jobs as well. And, of course, the electricity that the panels create can be used locally, saving energy costs, or sold to the grid, generating revenue.

“Agrivoltaics provide a rare chance for true synergy: more food, more energy, lower water demand, lower carbon emissions and more prosperous rural communities,” said Higgins. “Rural America, agriculture in particular, can be the solution to many of our concerns, whether it be renewable energy, mitigating climate change impacts, sustainable food or good water resource management. That connection is untapped mostly because there hasn’t been sufficient investment in those communities.”

Three basic needs: food, water and electricity. (Image courtesy of OSU.)

Higgins sees agrivoltaics as a long-term investment with substantial economic returns. With about a $1-trillion private-sector investment spread out over 35 years, he projects a 17-year payback period, after which the solar panels would generate more than $35 billion in revenue. In such a scenario, the federal government would provide tax incentives and rebates to encourage corporate investments during the construction phase.

The initial investment amounts to roughly one percent of the U.S. government’s annual budget. Throughout the nation’s history, every new technology with the potential to benefit society as a whole has received federal incentives and subsidies, so this is no different than the government’s role in building the fossil fuel industry during its infancy. In fact, the feds continue to subsidize fossil fuels to this day, albeit at lower levels than before.

To learn more about agrivoltaics, check out these resources from the National Renewable Energy Laboratory (NREL):