Combining Solar Energy And Agriculture Can Help Plants, Power, And People

Agrivoltaics - the combination of solar energy and agriculture on the same plot of land - kills multiple birds with one stone. It allows for more solar energy, more sustainable food production, and the conservation of precious land and water resources.

Story by

Danny Schleien

The amount of solar energy that hits the Earth’s surface in just one hour is more than enough to power our entire civilization for a year. Seeing as there are almost 10,000 hours in a year, the Sun’s rays are essentially an unlimited energy source. One challenge is that a typical solar panel can only convert about 20% of solar energy into electricity. Thus, to properly harness the energy of the Sun, you need a lot of solar panels scattered and pointed in optimal ways.

A bigger challenge is the space solar power requires. You can produce a good deal of electricity from solar panels mounted on roofs of residential or commercial structures. However, to really get the best of solar power, you need open space.In some areas, open space is abundant. In others, it’s not. That’s largely because we need lots of space to produce something else that’s pretty important: food. Despite centuries of optimizing food production, it still swallows about half of Earth’s habitable land. But all of that optimization can’t get around the eight billion mouths we must feed, and many of those mouths enjoy resource-intensive food like beef. Unless either one of those facts changes anytime soon, the amount of land we use for food production won’t change materially. So it would seem that our need to feed ourselves conflicts with our need to power our civilization with abundant solar energy. Well, what if you could combine solar power and agriculture in a way that makes both solar power and food production more effective while providing other massive benefits beyond the realms of energy and food?

It turns out there’s a burgeoning type of land use that involves just that: agrivoltaics. In a nutshell, agrivoltaics (i.e., agriculture plus photovoltaics) is the combination of solar energy and agriculture. It typically involves co-locating solar panels and some sort of food production, whether it be crops, livestock, and/or pollinators.

As you’ll see below, agrivoltaics kills multiple birds with one stone. It allows for more solar energy, more sustainable food production, and the conservation of precious land and water resources. This neatly ties into the food-energy-water nexus, a concept propagated by the United Nations which reflects the links between food security, energy security, and water security as well as their links to human well-being, poverty reduction, and sustainable development.

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Challenges To Agrivoltaics Adoption

Agrivoltaics isn’t cheap. You need to mount solar panels high enough above the ground to allow plants to grow as well as people and machines to roam. The upfront cost is high, which presents a major hurdle for small-scale farmers and ranchers who have struggled as the food industry consolidates, and external threats like climate change make food production more uncertain.

Agrivoltaics systems also entail careful coordination and planning. You need to pick the right crops to be grown and the right solar panels to produce power. And everything needs to be placed in a way that optimizes productivity. It’s critical to pick solar panels that won’t overexpose or underexpose the crops growing underneath to the elements. Even minor changes in sunlight exposure, humidity, or rainwater runoff can have drastic impacts on crop yield and solar panel efficiency. This often requires different farming machinery and electrical infrastructure, which can raise insurance premiums for farmers while presenting logistical challenges.

Plus, the aesthetics of solar panels don’t exactly align with the bucolic imagery of rolling vine-covered hills or grassy pastures that we think of when it comes to food. Many farmers and ranchers aren’t exactly too keen on disrupting their land with solar panels that they might see as expensive boondoggles that only interrupt their way of doing things.

As Hannah Ritchie, Head of Research at Our World in Data, described in a newsletter piece: “things that seem more grounded in ‘natural’ properties seem better to us. Or our ‘appeal to nature, where natural equals good and unnatural equals bad. We’re skeptical of synthetic stuff that comes out of a factory.”

‍That instinct is even more heightened when the “synthetic stuff” is directly juxtaposed with nature.

How Agrivoltaics Works Symbiotically For Plants, Power, And People

When you consider the nature of agrivoltaics, it becomes clear that it is best adapted to hot, dry climates where the Sun shines enough to make solar panels worthwhile but too much for certain plants to grow optimally. Think of solar panels on farms as manmade trees in a sense. Trees convert sunshine into oxygen. Panels convert it into power. Like trees, solar panels harness solar energy in a way that mediates surrounding environmental conditions.

Solar panels need sunshine, but too much sunshine can produce enough heat to impair their efficiency. Solar panels generate an electric current when the Sun’s photons knock electrons out of atoms, but if they overheat, the electrons get overexcited and generate less electricity when they’re ultimately dislodged.

Plants naturally transfer water to the atmosphere via a process called transpiration, which cools the surrounding air. By lowering ambient temperatures, plants can make solar panels more efficient. Agrivoltaics systems mimic a natural forest environment in which, other than the tallest trees, all plants can only soak up diffuse beams of sunshine that break through the tree cover.

Like trees, solar panels harness solar energy in a way that mediates surrounding environmental conditions.

The best crops for agrivoltaics tend to grow better with some shade. Since fruits typically grow on trees or vines high above the ground and grains prefer full Sun, vegetables like lettuce, sweet potato, alfalfa, and kale are often best suited for agrivoltaics. In short, the kinds of crops that tend to grow well in greenhouses also tend to work well in agrivoltaics. As a side note, this symbiosis makes agrivoltaics uniquely useful on rooftop farms, which tend to heat up quickly.

All the while, agrivoltaics systems present great opportunities for rural communities, which can benefit from locally sourced renewable electricity and obtain new revenue streams. Rural landowners can lease their land to solar energy developers or directly sell electricity generated by solar panels on their land.

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The Promise Of Vertically Mounted Bifacial Solar Panels

As with most solar farms, most agrivoltaics systems involve horizontally mounted solar arrays that are angled slightly upward to capture more of the Sun’s energy. However, there are other ways to harness solar energy that might work well for agrivoltaics. One innovative German company launched an agrivoltaics park in 2020 to produce 4.1 megawatts of power. The catch? Next2Sun mounted 11,000 solar panels vertically, meaning they jut up rather than side-to-side. And the panels are bifacial, meaning they’re double-sided instead of single-sided.

Two years later, in August 2022, researchers at Leipzig University of Applied Sciences published a study with a trailblazing claim that validates Next2Sun’s business model. According to the study, mounting bifacial solar panels with one side facing east and the other facing west would produce more renewable electricity and reduce one of the side effects of traditional solar energy farms: an abundance of electricity at midday and a shortage of electricity in the morning and afternoon when the solar angle is lower.

The plants also lost less water and grew more food. The cooling they provided to the solar panels increased the efficiency of solar energy production.

Whereas the supply of solar power in conventional systems peaks in midday when the Sun is highest, demand tends to peak in the late afternoon. By matching supply more closely with demand, the study found that vertically mounted bifacial solar panels would save Germany a lot of battery storage in a future that reflects the German government’s new ambitions of increasing the share of renewable energy in its economy to at least 80% by 2030. This scenario would also save more than ten megatons of carbon dioxide per year.

And by essentially creating a solar panel fence around a plot of land, vertically mounted panels allow for food production just like conventional agrivoltaics systems. Even better, this arrangement doesn’t require tall and expensive mounting systems that enable farm machinery to operate and plants to grow underneath. In densely populated countries like Germany, where renewable energy and agriculture often come into conflict due to a lack of land, this relatively new technology could help put that conflict to bed.

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What The Research Says About Agrivoltaics

University of Arizona professor Greg Barron-Gafford, a renowned agrivoltaics expert, led a multi-year study of agrivoltaics whose results were published in 2019. Barron-Gafford and his team created the first agrivoltaics research site at Biosphere 2, a scientific research facility located in the Arizona desert that remains the largest closed ecological system ever created. It’d be hard to design a better laboratory than Biosphere 2 to test innovative sustainability ideas like agrivoltaics.

To test the viability of agrivoltaics, professors and students grew jalapeno, cherry tomato, and chiltepin pepper plants, measuring a plethora of factors from plant germination to carbon sequestration to water use to food production. They tested incoming light levels, air temperature, and relative humidity above the soil and soil temperature and moisture levels five centimeters below the surface.

They found that the shade provided by the solar panels resulted in cooler daytime temperatures and warmer nighttime temperatures than traditional, open-sky planting. The plants also lost less water and grew more food. The cooling they provided to the solar panels increased the efficiency of solar energy production. And the forestlike shading that solar panels provide elicits a physiological response from plants. To collect more light, their leaves grow bigger than they would if planted in an open field, leading to higher crop yields.

Another 2020 paper published in the journal Sustainability demonstrated the land use benefits of expanding agrivoltaics just a bit beyond their current adoption level. Researchers concluded that using about 13,000 square miles of land (just 1% of current United States farmland) for agrivoltaics could provide 20% of total electricity generation in the U.S. And that level of agrivoltaics installation could reduce annual carbon dioxide emissions by 330,000 tons with minimal impacts to crop yield.

The paper’s senior author, Chad Higgins, wrote that agrivoltaics provide a “rare chance for true synergy: more food, more energy, lower water demand, lower carbon emissions, and more prosperous rural communities.” And Higgins believes widespread agrivoltaics adoption could spur other technologies, such as electric tractors powered by surplus solar energy and sensors that enable artificial intelligence-based decisions to improve agricultural productivity.

And one 2016 study found that the dual use of solar power and agriculture creates an increase in economic value above 30% from farms deploying agrivoltaic systems instead of conventional agriculture. Since the study’s results were based on old inputs that did not account for advances in solar power, in particular, it’s quite possible that agrivoltaics can actually create more economic value than the study concluded six years ago.

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How An Ex-Peace Corps Volunteer Used Agrivoltaics To Revive His Family Farm

After serving in the Peace Corps, Byron Kominek returned to his family’s 24-acre farm near Boulder, Colorado, worried about the farm’s future. Kominek approached Boulder County regulators about putting solar panels on his farm but was initially rejected because the farm was designated as historic farmland.

But with help from researchers at nearby Colorado State University and the National Renewable Energy Lab (NREL), along with some give-and-take with county regulators, Kominek developed a community solar garden named Jack’s Solar Garden (in honor of his grandfather) that now sells over a megawatt of power back into the local grid, enough to power 300 homes for a year.

The solar array was designed to optimize output while allowing people to operate under the panels, which were elevated at different heights to study the microclimate impact on the crops in regards to sunlight, shade, and irrigation.

Kominek realized that the shade provided by the panels helped the plants thrive. It also saved crucial irrigation water and cooled the panels, making them more efficient.

Kominek was initially nervous about growing food alongside his new solar panels in the spring of 2021. By the summer, he became a believer. Kominek realized that the shade provided by the panels helped the plants thrive. It also saved crucial irrigation water and cooled the panels, making them more efficient.

Kominek had literally bet the farm to finance the roughly $2 million solar arrays, putting the land up as collateral to get a bank loan. That fall, rows of peppers, tomatoes, squash, pumpkins, lettuces, beets, turnips, carrots, chard, and kale were harvested eight feet below the solar panels.

Today, Jack’s Solar Garden is a beacon for the local community. It donates power to local low-income households, promotes local artists, supports a large pollinator habitat (for the birds and the bees), hosts events and tours to show agrivoltaics to the public, and educates students on how energy and food can go hand-in-hand.

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Conclusion

Agrivoltaics adoption is still fairly limited globally. Total global capacity grew from about five megawatts in 2012 and 3 gigawatts in 2018 to more than 14 gigawatts in 2021, according to Germany’s Fraunhofer Institute for Solar Energy Systems. The world’s largest agrivoltaics system is in China, with solar panels on top of a massive berry farm on the edge of the Gobi Desert than can produce 700 megawatts of power.

Critics say that given the technological and logistical hurdles posed by agrivoltaics systems, it may never enter the mainstream. But with innovations in the pipeline and surging demand for renewable energy around the world, it’s certainly possible that agrivoltaics might evolve from a niche discipline to a popular way to feed and power communities around the world.

The need for these sorts of multifaceted climate solutions could not be more pressing. Seeing as much of the world is getting hotter and drier, agrivoltaics boost climate resilience wonderfully by creating more favorable growing conditions for plants while increasing the efficiency of solar power in hot and dry climates. By directly addressing the food-water-energy nexus with more sustainable land use, agrivoltaics can bolster the availability of humanity’s most indispensable resources. In essence, agrivoltaics is most useful where it’s most needed - in the Global South, where climate change is exacerbating resource shortages.

Ultimately, energy is the lifeblood of civilization. The misguided ways in which we produce and consume it explains much of our current predicament. As the world warms and the need for climate solutions grows, we may need to discard conventional wisdom and think out of the box to leverage human ingenuity for our collective benefit.

If we can produce and distribute energy more sustainably, we will go a long way toward alleviating many of our most urgent societal problems. It remains to be seen how broadly and how quickly agrivoltaics will be adopted around the world, but the bottom line is that climate solutions like agrivoltaics - which address a diverse range of concerns and benefit many people rather than a few - will win out in a decarbonized future.

Business Takeaways

The amount of solar energy that hits the Earth’s surface in just one hour is more than enough to power our entire civilization for a year.
Despite centuries of optimizing food production, it still swallows about half of Earth’s habitable land.
Using just 1% of current United States farmland (about 13,000 square miles) for agrivoltaics could provide 20% of total electricity generation in the U.S. while reducing carbon dioxide emissions by 330,000 tons with minimal impacts to crop yield.
One 2016 study found that the dual use of solar power and agriculture creates an increase in economic value above 30% from farms deploying agrivoltaic systems instead of conventional agriculture.

Combining Solar Energy And Agriculture Can Help Plants, Power, And People

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