Agrivoltaics Explained: Farming With Solar Panels (And Sheep!)

Featured photo: solargrazing.org

Solar power is the world’s fastest-growing energy source—and for good reason. It’s clean, renewable, and at this point, cheaper than any other way of making electricity. But there’s one problem: It takes up a lot of space.

According to the Brookings Institution, a solar farm needs at least ten times as much land as a fossil fuel plant for each unit of power it produces. The U.S. Department of Energy’s Solar Futures Study says by 2050, solar panels could take up over 10 million acres. That would leave 10 million acres less for other important uses, like producing food.

But what if this weren’t a conflict? What if crops and solar panels could use the same land at the same time? That’s the idea behind agrivoltaics.

What is agrivoltaics?

The word “agrivoltaics” is a cross between “agriculture” and “photovoltaics,” and that’s just what it means. It’s the practice of producing both food and solar power on the same plot of land. Other names for it are agrisolar, dual use solar, and low-impact solar.

Of course, many farms already have solar panels installed on the roofs of houses and barns. These panels provide power for the farm and, in some cases, produce excess power to sell to the local utility. These small-scale installations can be a source of extra income for farmers.

But agrivoltaics works on a much bigger scale. The solar panels aren’t just on buildings; they’re out in the fields, sharing space with crops or grazing animals. This means they can provide considerably more income for farmers. And this dual use allows farmers and utilities to work as partners, rather than competing for land.

How agrivoltaics works 

Combining plants with solar panels

Both plants and solar panels need sunlight to function. But for both, too much sunlight is harmful. Plants, especially cool-season plants, get stressed in hot, direct sunlight. Likewise, solar panels function less efficiently when the temperature is high. This can be a problem for utility-scale solar farms. Putting clusters of solar panels on large areas of cleared land creates a “heat island,” raising nearby air temperatures. This, in turn, hampers the panels’ performance.

Combining plants with solar panels helps solve the problem of overheating for both of them. The main way to do this is to install solar panels on frames that raise them high off the ground. Crops can then be planted underneath.

The panels filter sunlight during the hottest part of the day, protecting the crops from damage. The shade they provide lowers the air temperature and helps keep the soil moist by reducing evaporation. This is good not only for the plants but also for farm workers who are shielded from the blazing sun.

At the same time, the plants are helping the solar panels. As they draw in carbon dioxide for photosynthesis, they open the pores in their leaves, known as stomata. This releases water vapor, cooling the panels from below. The panels work more efficiently, and the crops stay healthier—a win-win.

Solar grazing

Another form of agrivoltaics is called solar grazing.

The solar panels are installed on pastures, and animals—usually sheep—graze around them. Sheep are short enough to fit under the panels easily and are comfortable in the shade they provide. The vegetation at the solar installation provides food for the animals, and its fences help protect them from predators.

And the utility benefits because the sheep keep the plants cropped short, so they don’t shade the panels. This saves the owners of the facility the trouble and expense of mowing.

Advantages to agrivoltaics

Agrivoltaics is good for farmers, solar producers, and the public. It provides both clean energy and food—two things we’ll need a lot more of as the population grows. And it does it all without increasing the use of land, a limited resource.

Increases land productivity

To meet our climate goals, the U.S. needs a lot more solar facilities. But currently, farms occupy nearly 45% of the nation’s land. It’s difficult to find room for new solar plants without impinging on existing farmland. With agrivoltaics, both uses can occupy the same land, maximizing its productivity.

A German study from 2020 explored the impact of agrivoltaics on land use. It found that putting potatoes and solar panels on the same land could improve its productivity by up to 86%. The plot produced only 83% as much solar power as it would if it were fully occupied by solar panels. But it actually produced 3% more potatoes than it would if it had potato plants only. Putting the two together—83% as much solar power and 103% as many potatoes—makes the land 186% as productive.

Maximizes the potential of solar energy

Agrivoltaics maximizes the potential of solar energy in two ways. First, it improves the performance of solar panels in hot regions. This means solar farms can get more energy out of the same number of panels. And second, it expands the number of sites where new solar installations can go.

Can result in higher yields

Growing crops under solar panels can help keep them healthy. It protects them from overexposure to the sun, as well as from heavy rain and hail that could damage them. This can improve the yields of various high-value and shade-tolerant crops, including berries, soft fruits, root vegetables, leafy greens, asparagus, and hops.

In one study in Kenya, cabbages grown under solar panels were up to 33% bigger than cabbages grown in full sun. Lettuce and eggplant saw similar increases in yield. And corn grown underneath the panels was both taller and healthier.

A 2019 study done in the Arizona desert found even bigger benefits. Growing crops under solar panels doubled the yield of cherry tomatoes and tripled the yield of chiltepin peppers.

Improves certain crops

Agrivoltaics can boost not just the quantity of vegetables grown, but also their quality. For instance, in the Kenyan study, the crops grown under the panels suffered less damage from UV radiation. According to the 2020 German study, sun protection can also improve the quality of wine grapes and apples.

Reduces water use

The shade solar panels provide helps soil and plants retain moisture. Because the air stays cooler, less water evaporates from the soil and transpires from plant leaves. This helps farmers conserve water—a critical resource as climate change has caused increased drought.

In the 2019 Arizona study, soil moisture levels under the solar panels were an average of 15% higher. In addition, jalapeño pepper plants lost 65% less moisture from their leaves. Tomatoes grown under the panels needed 30% less water, and peppers needed only half as much.

Additional source of income for farmers

For farmers, one of the biggest perks of agrivoltaics is the extra income. Leasing land to solar companies provides a steady income stream, something farming can’t always do. In any given year, pests or weather problems may lead to poor harvests.

At the same time, price shifts can reduce the value of crops or raise the cost of growing them. The revenue from solar leases helps farmers ride out these ups and downs, giving them added security.

Saves solar operators money

Agrivoltaics offers cost savings for solar operators, as well. When solar panels share space with crops, they can’t be crowded as closely together. This makes them easier to service, saving on maintenance costs. Solar grazing can also cut maintenance costs by reducing the need for mowing.

Has a positive impact on the environment

Any use of renewable energy, including solar, is a plus for the environment. However, agrivoltaics—particularly solar grazing—can be even more beneficial than other types of solar farms. Because there’s no mowing involved, there’s less disturbance to wildlife, such as ground-nesting birds. Avoiding mowing also cuts back on fossil fuel use and the emissions it causes.

In addition, agrivoltaics can help support pollinators, such as bees and butterflies. Solar panels combine well with pollinator-supporting plants such as wildflowers and prairie clover. Farmers can seed fields with these plants to attract pollinators for their other crops. Scientists are also studying how agrivoltaics and solar grazing might help with carbon sequestration—storing carbon in soil.

Does agrivoltaics have any disadvantages?

Although agrivoltaics has obvious benefits, it’s not a no-brainer. Not every farm is better off with solar panels, and not every solar farm is better off with crops.

Loss of productive land

Often, the raised racks solar panels rest on can’t sit directly in the dirt. To install them, utilities must strip away topsoil and install concrete pads. This leaves the farm with less productive space, and it’s hard to restore it if the solar panels are removed.

Limits on machinery use

It can be difficult for farm machinery to fit underneath an agrisolar array. Even though the panels are raised off the ground, they limit the size of the equipment that will fit underneath. And even machinery that fits easily may find it harder to maneuver around the racks.

Limits on available crops

Not all crops grow well under solar panels. The combination works very well for plants that like partial shade, such as leafy greens, root vegetables, and alfalfa. But other crops require full sun to flourish.

A 2021 study found that yields of winter wheat, potatoes, and grass-clover can all fall when they’re grown with agrivoltaics. Other experiments at the University of Massachusetts found that peppers, broccoli, and Swiss chard grown under solar panels produce only about 60% of the yield they would in full sun.

Less total power output

Just as agrivoltaics can also reduce crop production, they can also reduce solar production.

It’s true that each individual solar panel produces more power thanks to the cooling effect of the plants. However, fewer panels can fit on each acre of land. As a result, agrivoltaic solar farms produce less total power per acre than dedicated solar farms. So, in areas where land is plentiful, it can make sense for solar farms to have their own space rather than sharing land with farms.

Is agrivoltaics the future of farming?

The answer is both yes and no. It’s certainly likely that an increasing share of farms will include solar setups in the future. However, it’s unlikely that agrivoltaics will ever take over all farms.

As noted above, not all crops work well with dual-use solar. Many important crops, such as wheat, can only grow well in full sun. Others, including many fruits and nuts, grow on trees that are too tall to fit beneath solar panels.

It probably makes the most sense for solar panels to share space only with crops that can thrive underneath them. Which crops these are will vary from region to region. Leafy greens and root crops, such as potatoes and beets, can perform well with dual-use solar almost anywhere. Berries have also performed well in some studies. And in hot climates, tomatoes and peppers are good choices as well.

Another limitation of agrivoltaics is that it doesn’t combine well with greenhouses—at least not yet. When scientists tested a greenhouse design with half the roof covered with solar panels, it reduced crop yields by over 60%. In addition, the power output of the panels was lowered by more than 80%. But scientists are continuing to search for ways to use solar panels in greenhouse design.

Agrivoltaic farming in the U.S.

In the meantime, many farms across the U.S. are forging ahead with dual-use solar projects.

Currently, the largest such project in the country is on a blueberry farm in Rockport, Maine. On ten acres of this farm, the berry bushes share space with a 4.2-megawatt community solar farm. Scientists from the University of Maine are testing a variety of solar setups here to figure out the right setup is for both the panels and the plants.

Other agrivoltaics locations in the U.S. include:

• A sheep farm in Maine
• A cattle ranch in Vermont
• Research projects at Cornell University, Rutgers University, the University of Arizona, the University of Vermont, and the University of Massachusetts Amherst
• Facilities in 11 states run by the government-funded InSPIRE Project

The potential of agrivoltaics

Agrivoltaics has the power to transform both traditional farming and solar power production. Rather than competing for limited land resources, farmers and solar developers can be partners. They can work together to plan agrivoltaics projects that maximize the output of both food and energy. This way, they can simultaneously increase the food supply and speed the transition to a clean energy future.