The Pros and Cons of Agri-PV: Cultivating crops under solar panels
Reduced crop damage, better harvesting conditions, no more hassle with flapping plastic, and an overall more aesthetically pleasing appearance. Solar panels above crops offer numerous benefits. However, the widespread adoption of this technology has yet to take off. The main challenge: the financial calculations.
Earlier this spring, there were a few days with strong winds and heavy rain. Red currant grower Rini Kusters in the village Wadenoijen, the Netherlands, is less worried about such weather than he used to be. In the past, even a slight breeze would cause the plastic covering his crops to flap around. “We would spend hours repairing the damage, only for it to happen again a week later.”
Since 2021, 1.8 hectares of his crops (out of a total of 6 hectares) have been covered with solar panels. These panels protect Kusters’ red currants from hail, rain, and wind, making his product more sustainable as well. “Fungal diseases are the biggest challenge in red currant cultivation, particularly botrytis, which often appears in wet weather. The berries under the panels receive little rain, so there are fewer fungi, and I need to use much less pesticide now.”
Improved working conditions
Agri-PV (PV stands for photovoltaic, another term for solar panels) combines agriculture with solar energy production. In the Netherlands, only a handful of growers have solar panels above their crops, allowing them to simultaneously grow fruit and harvest solar energy. Besides protection from wind and rain, the panels offer many other advantages.
It’s always a few degrees cooler under the panels than in full sun or under plastic sheeting
Piet Albers, a raspberry grower, knows this well. He was the first Dutch grower to cover his crops with solar panels in 2018. “Since then, we’ve had much less trouble with fruit sunburn. Summers are getting hotter, so the panels also improve working conditions for pickers during heatwaves. It’s always a few degrees cooler under the panels than in full sun or under plastic sheeting.”
For Kusters, the appearance is also a reason to switch from flapping plastic to solar panels. “It looks better and less messy. Our neighbors are enthusiastic.” He also notes an improvement in biodiversity: “I see many more bees and butterflies. Bees used to get trapped in the plastic, but now they buzz freely among the plants.” Kusters receives many visitors interested in the setup: “Last year, I gave tours to about 800 people, from the Netherlands and beyond, including growers, researchers, and politicians. Everyone loves it.”
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Commercial challenges
Despite all the benefits, the major breakthrough for agri-PV still seems elusive. The main reason: it’s difficult to make the financial calculations work. This isn’t an issue for growers like Kusters and Albers, who are participating in a pilot project with GroenLeven, a subsidiary of the German company BayWa. GroenLeven develops innovative energy solutions, including solar and wind energy. They own the solar panels and have handled the construction, which quickly costs around €90,000 to €100,000 per hectare. They are also responsible for panel maintenance, obtaining permits, applying for subsidies, and negotiating with energy companies that purchase the electricity.
Per-Hectare compensation for growers
Of course, the developer receives all the energy revenues and pays the growers an annual fee per hectare for the use of their land. The growers can’t disclose the exact amount. GroenLeven’s agri-PV project manager, Bram Wasser, explains: “With Kusters and Albers’ projects, we want to learn from agri-PV with fruit and explore how it can work on a commercial scale. Technically, the system is fully developed; we now know the yields of solar panels above fruit cultivation, the construction challenges, and how to address them. But there are significant commercial challenges. The construction, for example, is relatively expensive because it needs to be tall enough to accommodate the plants underneath. This requires a lot more steel.”
Translucent solar panels
Another key reason why solar panels above fruit produce less energy is that they are partially transparent to allow crops to receive the necessary sunlight. Herman Helsen, a researcher at Wageningen University Research, puts it well: “Sunlight can only be used once, either for electricity or for plant growth. The need to share light between these two purposes is often underestimated.”
According to Helsen, this principle applies almost universally in agri-PV research. “We know that removing light reduces crop production. Data is now available on agri-PV with crops like strawberries, raspberries, red currants, and pears. For each crop, we investigate how much light the panels must allow through to minimize production loss.” Helsen’s research also looks at factors like flower bud development, leaf shape, and leaf thickness of the crops. Is the steel frame of these panels healthy for the soil and crops? Helsen says, “Yes, as long as certain foundation requirements, which vary by municipality, are met. Ultimately, solar panels do affect soil life because the ground under the panels remains dry for extended periods. This is also part of our research.”
Sunlight can only be used once, either for electricity or for plant growth
Albers has seen how critical transparency is. Over the years, various panels with different transparency levels have been tested on his land: “The first panels allowed 11% of light through, and I barely harvested any raspberries. The next generation was 25% transparent, which economically broke even: the solar yield compensated for the crop loss. Now we have panels that let 40% of light through. They work well, although the yield varies by year. This year, I expect a 5% reduction in production, which is manageable.” However, Albers has noticed that the ground is much muddier this year: “Rainwater runs off the panels into the area where we work. It’s not ideal for pickers or machinery.”
According to Helsen, production loss doesn’t have to be disastrous: “As long as the cost structures of both the crops and the solar panels are independently viable. If either the grower or the solar panel owner lacks a sustainable business model, you end up with a flawed system. So, it’s about finding the right balance where both parties benefit.”
Going solo with Agri-PV?
Do growers always need to rely on developers, or can they implement agri-PV on their own? Kusters is skeptical that growers can cover all the costs themselves: “Without an investor, it’s not feasible. Banks are very cautious.” At GroenLeven, they’re not eager to expand this form of agri-PV either, says Wasser: “We receive many inquiries from growers. We’re always open to discussions to see if we can develop something with a grower. But the margins for solar panels over fruit are so small that we currently only build or develop large projects, starting at 10 hectares.”
One option to ease the financial burden for growers is subsidies, but these aren’t easy to obtain, explains Wilma Eerenstein, project manager of Sunbiose, a project where multiple parties are researching agri-PV: “At the moment, there’s one Dutch grower who has set up the entire system on his own. But he was able to use an innovation subsidy for the investment, created to demonstrate the effectiveness of this form of agri-PV. Similar projects can’t tap into that fund.” Eerenstein believes that the financial equation could become more attractive if the compensation is increased.
