A win-win is always welcome. But what about a win-win-win? Researchers say that’s what’s possible with agrivoltaics, a groundbreaking system that combines solar energy with agriculture. Some refer to it as “dual solar” or “solar sharing.”
The win-win-win here is the ability of agrivoltaics to increase food production, boost renewable energy production and achieve important water savings — all on the same piece of land.
A cutting-edge technology, agrivoltaics, differs from typical large-scale utility installations of solar panels, which are typically placed close to the ground with gravel underneath them. While these can generate a lot of energy, they take a lot of crop land out of the mix. And with the world’s population continuing to grow and expected to reach 8.1 billion by 2025, according to the United Nations, the demand for food will increase. Agricultural researchers say that covering crop land, or land that could be growing crops, just doesn’t make sense.
That’s where agrivoltaics comes into the picture. Instead of placing the panels close to the ground, they’re positioned about 7 to 10 feet above the ground. There’s also some spacing between the “clusters” of panels, thus providing a mix of shade and sun to the plants.
The shade pattern moves during the day so that all of parts of the growing area receive direct sun during each day, which allows the amount of reflected sunlight to be maximized.
At the same time, the crops do better in the shade — compared to a full day of direct sunlight.
One of the benefits to this is that the land and the air under the panels is much cooler in the summer and warmer in the winter.
Another plus is that solar panels cost much less now than they did 10 years ago, thus spurring interest in this new technology.
The ‘sweet spot’
As strange as it might seem, too much sunshine — not just in drought conditions, but also in normal growing conditions — can be hard on plants. That’s because plants can use only so much sunshine. Any sun received after that “point of light saturation” doesn’t help the plant grow or even increase photosynthesis. Instead, it increases the plant’s need for water. In other words, the plants becomes thirsty and want more water. This, in turn, means they need to be irrigated more.
But with agrivoltaics, the panels can be positioned to give the plants just the right amount of sunlight and shade. And this, in turn, allows the excess sunlight to be harvested for electricity. The advantage here is that this system can produce up to 10 percent more electricity, according to field trials done in several states.
This surplus electricity can then be sent to the grid for consumers’ use or stored in batteries to run electric tractors and equipment or to supply electricity to the owner’s house and/or barn.
“The sweet spot” is how University of Massachusetts agronomist Stephen Herbert, author of “Growing Vegetables Under Solar PV,” refers to the positioning that allows maximum sun to reach the ground so the vegetation gets what it needs while the rest is captured for generating electricity.
Or as the National Renewable Energy Laboratory website puts it: “Beneath solar panels, the seeds of opportunity sprout.”
Ah, shade, blessed shade
Anyone who has been out in the sun for too long, knows how wonderful it is to escape into the shade. Some water, yes, but certainly not as much a “thirsty” crop would need for irrigation.
Field trials done in an Oregon State University Extension project, showed that each irrigation event in an agrivoltaic system can support crop growth for days instead of just hours as in a typical agricultural setting.
In one field trial, when irrigating every other day, the soil moisture stayed about 15 percent higher in the agrivoltaics system than in the control plot.
Not only that, the shade provided cooler daytime temperatures and warmer nighttime temperatures than in the conventional setting.
The news was also good for crop production in a trial “salsa garden.” Total chiltepin pepper production was three times greater in the agrivoltaics system than in the control setting. And cherry tomato fruit production doubled.
Growing crops in an agrivoltaic system was also good for the panels, because it helped keep them cool. This, in turn, made them more efficient. Solar panels actually lose efficiency when they get too hot.
Suitable crops to grow this way are lettuces, tomatoes, peppers, chard, kale, broccoli and Brussels sprouts, and some herbs as well as bedding plants, nursery crops, and short-statured fruit trees or shrubs. In addition, small-to-medium sized livestock could be grazed in land separated from the crops. Not goats, though, they’re too frisky.
Bees also like agrivoltaic settings. One beekeeper said he gets a premium price for his honey because customers appreciate the environmental benefits of agrivoltaics.
However crops that need a lot of sunlight, for example, watermelon, eggplant, corn and certain types of pepper, might not be as successful.
Bottlomline, more research needs to be done on how various crops will grow in an agrivoltaic system and what regions they will work well in.
A recent OSU study estimates that converting just 1 percent of American farmland to agrivoltaics would meet the nation’s renewable energy targets, save water, and create a sustainable long-term food system. In addition it would give farmers more economic opportunities, which would help keep farmland in production. This translates into benefits for consumers. More food means healthier people and therefore less malnutrition.
In contrast, the typical solar power installation, where the panels are close to the ground and the land covered with gravel, is no slam dunk when it comes to renewable energy. Far from it. It would take 32 acres of land to provide electricity for 1,000 homes.
According to the National Renewable Energy Laboratory, by 2030, utility-scale solar could cover almost 2 million acres of land in the United States. The problem with this is that traditional solar development would monopolize this land for just one use: energy
Ask a farmer
Massachusetts farmer Paul Knowlton knows all about the value of solar energy. He already has 18,000 solar panels on 19 acres, which provides enough clean energy for almost 1,200 homes. It’s a cash crop for him.
But now he’s going to go one step further. He plans to expand solar on his farm to another 14 acres. But this time, he’ll be using agrivoltaics.
The solar panels will be mounted on racks about 8 feet off the ground, a height that will allow farm machinery to operate under them. And, of course, this will also allow him to grow crops underneath them. This way he’ll get a “double crop” off the land: energy and food.
Another plus to this sort of setup is that farmworkers will be able to stay cooler. Preliminary data show that skin temperature can be about 18 degrees cooler when working in an agrivoltaics setting than in a traditional setting. That’s important because in the Southwest, for example, farmworkers suffer a troubling number of heat strokes and heat-related deaths.
Iain Ward, a solar expert and land planner who helped design this new system for Knowlton’s farm refers to it as groundbreaking technology. The panels in this project are an innovative translucent design. While the top of the panels absorb the sun’t energy, they also let some light through. And because they can capture the sunlight reflected off the ground, they’re more efficient.
A state SMART program, which offers grants to expand conventional solar and jump start dual-use technology, is funding the project. State officials are hoping to set up 18 to 19 projects to be ready for the upcoming farm season.
As is the case with most farmers, Colorado farmer Byron Kominek, owner of Jack’s Solar Garden near Boulder, CO, likes his tractor. But he also likes knowing that tractors and agrivoltaics make a good team.
“The idea that our land can do more than just create electricity, that we can also figure out how to produce food in combination with our solar array is very interesting,” he said.
“Society needs to figure out how to get the most good from our natural resources while not depleting them — in fact, we need to figure out how to best use them while improving them, which is a possibility with agrivoltaics.
This year he’ll be planting his first crops in an agrivoltaic setup on his farm — 30 different crops, along with prairie grasses and wildflower seed mixes, on 5 acres.
“I was looking for something else to do,” he said, referring to previous years of growing hay and grasses for livestock — something his farm has been doing since 1972. “We want to move forward.”
Kominek is also enthusiastic about “spreading the word” about the value of agrivoltaics and the benefits it offers to farmers and communities.
Jack’s Solar Garden will educate the next generation by offering regular school tours under its solar panels. Farmers, government officials, students and the public will be invited to tour the farm. The goal of these tours is to publicize the possibilities agrivoltaics offers to society.
“With the innovativeness and openness we offer, we hope to inspire our community to support local farmers as they embark on creative paths to better our community with locally produced foods and solar power,” says the farm’s vision statement.
For more information about volunteering at or touring Jack’s Solar Garden visit his website.
Kominek is working on his farm’s new endeavor in partnership with the National Renewable Energy Laboratory, Colorado State University and the University of Arizona.
Go here for a farmers guide to going solar. This site has a long list of questions (and answers) that farmers might have.
Go here (https://openei.org/wiki/InSPIRE/Project) To read more about the efforts to site solar and agriculture through the Energy Department’s InSPIRE project.
What about food safety
Stephen Herbert, professor of agriculture at the Stockbridge School of Agriculture in Massachusetts, said he doesn’t see any more of a problem when it comes to food safety than in conventionally grown crops, as long as there is ample air circulation and the shade pattern moves during the day so that all of parts of the growing area receive direct sun during each day.
The minimum gap distance he would recommend is 4 feet with solar panels arranged horizontally.
“And since most solar installations are fenced, most wildlife would be excluded, further ensuring food safety,” he said.
This is an important consideration because wildlife wandering through crops often leave droppings. In a case in Oregon in recent years, some people became ill and one person died after eating strawberries contaminated with E. coli from deer droppings in the field.
Don Stoeckel, a researcher with the Produce Safety Alliance, has questions about wildlife when it comes to food safety. He wonders about wildlife incursion and how the solar infrastructure would affect this. For example, do birds roost on the panels or support structures, thus causing a risk to any produce growing underneath. And what about rodents? Do they seek shelter in the shade cast by the panels?
Food safety expert Trevor Suslow, Emeritus Extension Research Specialist at the University of California-Davis, who specializes in pre-market and post-market produce quality and microbial safety, said that specialty crops rarely consumed raw — in other words, usually cooked, which kills foodborne pathogens or non-food crops, such as ornamental crops — “might be a better target for proof of concept” of agrivoltaic technology.
He pointed out that any crop production system conducted in an open environment is susceptible to potential and diverse sources of contamination, not effectively prevented by fencing or screening.
“Agrivoltaic sites and structures should be evaluated for their potential to provide roosting and nesting sites for birds or other potential vectors of foodborne pathogens,” he said. “
Shading can reduce water use and even, potentially, reduce some solar injury in crops at sensitive stages, sun scalding of fruit vegetables, for example, Suslow said.
But on the flip side, he said that shading is known to increase the potential for persistence of zoonotic bacterial pathogens on the surface of a crop — lettuce and spinach for example — and shading also alters the growth habit, surface structure, cuticle thickness, and other plant aspects shown to potentially increase pathogen attachment, survival, and internalization.
In addition, the said that too much shading at key developmental stages may result in thinner leaf structures or thinner fruit wall structures, leading to reduced shipping and shelf life.
While he can appreciate the advantages offered by agrivoltaics, Suslow said it’s important to make sure that “food safety and quality are part of the mix.”
The global map
Japan has been the pioneer in agrivoltaics. Between 2004 and 2017, more than 1,000 open field power plants were developed in that country.
Some of the other countries using agrivoltaics are China, South Korea, India, Malaysia, Vietnam, Austria, Italy and France.
Some researchers say most people don’t realize how much agrivoltaics is going to change the “global map of agriculture” in the future.
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