The ongoing debate of whether solar arrays installed on farms take that land out of production is being challenged by a 4.5-acre farm in Exeter, Rhode Island. Our Kids Farm partnered with renewable energy company Green Development to independently test the viability of growing crops underneath and near solar panels.
“We really firmly believed that solar was good for a farm and could be dual cropped,” said Gina Thurn, owner of Our Kids Farm.
Green Development installed a 20-kW solar array at on a half-acre plot on the property where Thurn and her husband Loren maintain outdoor crops and greenhouses.
Back in 2017, solar projects started coming to Exeter and were primarily being installed on farmland. Farmers were leasing land for the ground-mounted solar arrays to generate extra income, but residents, who Gina Thurn noted mostly worked outside the agricultural industry, opposed the installations.
“Between the weather and crop values, there were a lot of farms that weren’t making it,” she said. “We had been active in our town council meetings because our town has tried to put an agriculture overlay ordinance that essentially would have put us out of business. That’s where solar came into play.”
The Thurns frequently testified in favor of renewable energy growth in the area. Rhode Island’s 39 cities and towns each have differing regulations for solar, like ground-mounted systems being restricted to commercial land, or height and footprint limitations on arrays.
“Even if you don’t do dual-use, this is helping you survive. I think a lot of farmers around here get really annoyed that there are so many regulations saying what they can and can’t do with their property,” said Jeanne Heston, director of marketing and communications with Green Development. “They can sell it to a housing developer more easily sometimes than they can put in a solar development that will be taken out in 25 years.”
Mark DePasquale, CEO of Green Development, spoke at a council meeting in 2018, proposing that he was willing to work with a farm to create a dual-use array to test crop growth under solar panels.
The Thurns volunteered to be that farm.
Designing a dual-use array
Green Development typically installs utility-scale solar projects. Scaling down and constructing a 20-kW system on a piece of property that hosts both a residence and commercial business presented its own challenges.
Two utility services held jurisdiction over on-site meters at Our Kids Farm and had to be removed then combined into one service to interconnect the PV system.
The array is composed of SMA Sunny Boy 6-kW inverters, Yingli 320-W, 72-cell modules and a RBI Solar GM-2 (ground mount) racking system. The three-row array is offsetting energy costs that will be reinvested into replacing oil heaters that are used in the greenhouses with an electric alternative. Gutters were attached to the array to redirect stormwater falling between panels and off the panel edge to a cistern to protect new plant growth, and that water can be reused for irrigation. The system itself is built 4 ft off the ground for easier access to plants underneath — the maximum height it could be installed according to local ordinances.
The panels were set in Spring 2019 and Thurn planted crops beneath by May. The system officially came online in October.
Growing food crops under panels
The Thurns purchased Our Kids Farm 13 years ago, leading into the 2008 recession. In the last decade, they’ve had to adapt to the economic turbulence of being a farm in the 21st century.
At its start, Our Kids Farm was focused on growing annual and perennial crops and selling hanging baskets, but the grow season was short, and they weren’t seeing any profits. They added greenhouses to farm year-round and create another source of revenue.
“We were at a point on our farm where we were struggling dramatically,” Gina Thurn said. “Within six months, the economy had crashed, and half of our assets were gone. We had spent all of that time trying to keep our head above water, trying to be as innovative as possible.”
Our Kids Farm has grown salad greens, lettuce blends, arugula, squash, cucumbers, eggplant, peppers, tomatoes and strawberries. The next major addition would be solar.
Under the array itself, and outside the greenhouses, 90% of the crops are planted in containers. The first year, they used a black setting cloth underneath the pots, and this year have switched to a white cloth for a more reflective surface that directs refracted light bouncing up to the panel backsheet back onto the plants.
With the south-facing array, the crops have been planted in rows east to west. Thurn said this is to simulate the most logical motion for moving through inner row spacing for crop cultivation. With certain crops, like kale and other leafy greens, the partial shade is beneficial and prevents scorching from mid-summer sunlight. The plants underneath the array are mostly grown hydroponically to ensure there are consistent conditions for the dual-use test.
Lettuces, arugula and mixed kales that are typically planted early in the season have extended their seasonality under solar panels, growing in spring, summer and fall.
“Sometimes it’s going to be doing trials, a lot of different things, to find out what works best in your area and what will tolerate a little more shade,” Thurn said. “Any farmer is going to plan their fields ahead of time. You need to do the same when you’re planting under a solar array.”
Our Kids Farm is approaching the end of its second growing season with the solar array, and Thurn is convinced dual-use solar farms could be applied at a larger scale.
The major difference in scaling up would be making the array taller to allow farmers to work the soil underneath. The ground is compacted at the time of installation and tilling equipment couldn’t fit under the 4-ft-tall array at Our Kids Farm. Allowing more space between rows would help as well, Thurn said, but the larger concern for scaling up would be removing restrictions around how large an array’s footprint and height can be.
“If the panels are paying for the ground already, is a reduced crop yield acceptable? Do I have to get 100% of my crop value, or is 80% OK? Whereas before in an open field, you needed 100% and then some, and even then, they weren’t covering the bills,” Thurn said. “With solar on your property, your bills are being covered for that space, so now your crop becomes a bonus.”
The Thurns are documenting their findings and plan to publish an official research paper at the end of the test. But their immediate goal is to take the information they’ve gathered so far and share it with town councils and planning boards to make dual-use farms a reality in Rhode Island.