Sharing land: Can photovoltaic energy and agriculture coexist?

Posted: November 15, 2024

At Rutgers University Animal Farm in New Brunswick, New Jersey, at the Rutgers School of Environmental and Biological Sciences (SEBS), a herd of cattle grazes on a three-acre grassy field shaded by 378 vertical bifacial solar panels. The first of its kind in New Jersey, the installation can generate electricity whether the sun hits the front or the back of each panel while leaving room in the field for agriculture.

Rutgers University’s scientists want to understand how farmers could host this new type of vertical solar panel in their fields while continuing to graze cattle or cultivate crops. “We define agrivoltaics as systems that allow for a more diverse range of agricultural or horticultural practices, including grazing large animals, producing staple and specialty crops, and hay,” said David Specca, Assistant Director of the Rutgers EcoComplex and lead of the Rutgers Agrivoltaics Program to Rutgers reporters.

The Solar Futures Study estimates that solar energy could contribute 1 terawatt of electricity-generating capacity to the U.S. grid by 2035, necessitating approximately 5.7 million acres of land. While this represents less than 0.3% of the total U.S. land area, it poses potential conflicts with agricultural land use since the attributes favorable for solar energy—ample sunlight and flat terrain—are also ideal for farming.

Integrating solar energy production and agriculture through agrivoltaics presents a promising solution to land use challenges, particularly as the demand for clean energy and food continues to rise.

The rise of agrivoltaics

Agrivoltaics is an emerging method that uses the same land for solar energy production and agriculture, and it is becoming increasingly popular across the U.S. The National Renewable Energy Laboratory has so far identified 589 agrivoltaics projects developed across 62,429 acres, representing over 10,082 MW of solar capacity. At the same time, the land is dedicated to grazing, pollinator habitat and growing staple crops, such as corn and soybeans, vegetables and hay.

The dual use of land for solar energy production and agriculture isn’t a new idea. The concept was first introduced by Adolf Goetzberger, founder of the Fraunhofer Institute for Solar Energy Systems in Germany, and his colleague Armin Zastrow in 1981 when the pair published a pioneering paper titled Kartoffeln unter dem Kollektor (Potatoes under Panels).

In 2010, researchers at the French National Institute for Agricultural Research (INRA) near Montpellier in France built the first agrivoltaics research farm. They experimented with crops grown under three conditions: full sunlight, beneath a standard photovoltaic array mounted at a height of 4 meters above the ground, and under half-density arrays that allowed more light to penetrate.

The group found that some crops, such as lettuce, might lose productivity under the full density panels but thrived just as well, if not better under half-density panels than exposed to full sun. They learned that crop growth can slow down when the plants are young, so some crops might need changes in how they are grown. They also discovered that crops that grow quickly and cover the soil can catch more sunlight, keep the soil cooler, reduce water evaporation, and require less watering.

"The panels protect the soil and crops from excessive sunlight, which reduces their water requirements by 20% to 30% and represents a significant saving in irrigation costs. They also limit the risk of crop scorching in the event of heatwaves, while protecting them from hail and tempering the effects of frost," Christian Dupraz, the INRA researcher leading the project told LUM Magazine.

Encouraged by these results, researchers from the Fraunhofer Institute in Germany set up an experiment with bifacial solar panels on a third of a hectare of farmland near Lake Constance for a capacity of 194 kilowatt. These panels were mounted one meter higher than the French setup to maximize sunlight exposure for the crops and accommodate large farming equipment underneath. In 2016, they connected their solar pilot plant to the grid and planted winter wheat, celeriac, potatoes, and clover beneath the panels.

After one year, the combined yield of food and electricity was 60% higher per square meter than if each had been cultivated separately. Clover performed particularly well, showing only an 8% drop in productivity compared to clover grown in full sun. Potato, wheat, and celeriac yields were lower by about 20% compared to plots without solar panels. However, yield for potatoes and wheat under the solar arrays were 2.7% and 11% higher than the yields of the crops under the sun during the hot, dry summer of 2018. Overall, the energy generated significantly outweighed agricultural losses, providing enough power for 62 homes over a year.

Other researchers have looked at solar panels on land used for everything from berries in Italy to apple orchards in France to sheep grazing in the U.S.

Agrivoltaics’ potential in a nutshell

Back in New Jersey, agrivoltaics is presenting an opportunity to advance the state’s renewable energy objectives while causing minimal disruption to the nearly 10,000 farms spread across 750,000 acres of preserved land.

But as research from France and Germany shows, the co-location of solar panels and agriculture holds many potential benefits for countries across the world.

Co-location of solar panels and agriculture could:

• Increase land use efficiency;
• Increase crop yield;
• Reduce plant drought and heat stress and increase plants’ climate resilience;
• Reduce solar panel heat stress;
• Increase farmers’ revenue through diversification of income sources;
• Improve biodiversity preservation by creating habitat for pollinators and native grasses.

“The technology offers several advantages, including reducing the operating costs for farmers by covering some or all of their electric costs,” A.J. Both, a professor and extension specialist in the Department of Environmental Sciences at SEBS, told Rutgers reporters. “It also contributes to reducing society’s carbon footprint and helping maintain farmland in active production.”

Laura Lawson, Executive Director of the Rutgers New Jersey Agricultural Experiment Station, added, “This new technology has the potential to produce renewable energy needed to reduce our carbon dioxide emissions while simultaneously making our family farms more viable and sustainable.”