Solar modules take a note from plant life, following a similar pattern of absorbing sunlight, processing it and producing energy (or in a plant’s case, creating nutrients that are consumed and converted into energy). Now, solar companies are pairing the photo-cousins to explore better land use practices and the possible benefits of growing crops under or near solar panels.
Saffron blooms underneath a solar panel in Vermont, its red stigma awaiting harvest. The University of Vermont and local solar developer Peck Solar are testing how the valuable spice will fare while paired with a solar array. University of Vermont
The Center for Saffron Research & Development at the University of Vermont (UVM) started growing the lucrative crop of its namesake underneath solar panels about a year ago after Steve Yates, project director at local solar EPC Peck Solar, approached the center with an idea and some money. Peck Solar provided grant funding for a two-year research effort to plant saffron bulbs underneath a 150-kWac/220-kWdc solar array at the Gervais Family Farm in New Haven, Vermont.
“The hope would be that it could be demonstrated that a crop can be produced economically on that same area,” said UVM entomologist Margaret Skinner. “It’s good for the environment, it’s good for the farmer whose land it is and it’s good for the solar people that are putting up arrays.”
Saffron is a crocus generally harvested in arid climates. The spice is historically grown in the Middle East, Italy and Spain, but was also harvested in the United Kingdom and grown by the Pennsylvania Dutch in the 1600s. Saffron is a late-season crop, blooming well into autumn in the United States.
“Our hope is that we can show that the land is still agriculture and we can create a viable crop and bring a market and be able to say, ‘No, this has not taken the land out of agricultural use,’” Yates said. “It’s keeping agriculture in use, in fact. We can double the value of this land to the farmer.”
Saffron was planted in 12 test beds, made of three rows of four—the first in front of the solar array, second under the panels and third behind them. The spice made it through its first grow season in Vermont, and the test will finish after the next. Peck Solar
The soil that saffron bulbs are planted in can be walked on, allowing for easy array maintenance when not in bloom; and shallow-rooted crops can be planted above saffron during the offseason.
It’s also the most sought-after spice in the world, trading at up to $5,000/lb.
Saffron’s value stems from how little can be harvested per plant and from its culinary and supposed medicinal applications. The deep red stigma of saffron in bloom, which only grows in threes in the center of the flower, are harvested during a sunny morning and subsequently dried.
“The beauty of saffron over some of the other crops is it’s a pretty easy, low-maintenance crop, except when you’re picking and processing the flowers,” Skinner said. “Once you get a good saffron bed established, they can sort of take care of themselves. In my mind, it is an ideal partnership for solar arrays.”
The simplicity of growing saffron along with its possible return on investment is why Peck Solar chose the crop for its dual-land-use experiment. The Center for Saffron Research has been exploring the possibility of growing saffron in the Northeast for four years and can show regional solar engineers that they can look beyond “counting kilowatts.” They can expand planning on agricultural sites to include crops like saffron with solar panels, Skinner said.
The Gervais Family Farm solar array was installed in December 2014, and the saffron was added in August 2018. The solar install consists of 748 Trina 295-W modules set in portrait orientation in Schletter FS racking, and its energy output goes to a local municipal building.
Saffron isn’t the sole solar and agriculture coupling in the United States. In North Carolina, honeybee hives sit among a pollinator-friendly solar array; and sheep graze underneath raised ground mount solar panels.
“We see solar and agriculture as working well together,” said Olivia Campbell Andersen, executive director of Renewable Energy Vermont. “Some of the projects that have been deployed in Vermont show how well they work.”
Green field and mountain state
According to the Census of Agriculture, in 2012 there were 1.25 million acres of farmland in Vermont, composing about a fifth of the state’s total land mass. That number has decreased, and the land sold since has likely been commercially developed, but some farmers are staying in business by leasing fields for solar arrays.
The 150-kWac/220-kWdc solar array was built on a plot of greenfield on the Gervais Family Farm in 2014. Peck Solar
However, the agricultural community is concerned land that could be used for crops is sacrificed for solar installations. UVM and Peck Solar’s saffron and solar experiment aims to prove it’s possible to grow profitable crops below ground-mount solar panels in green fields.
“What we found is the saffron that’s growing directly under the array actually is stronger, healthier, more abundant than that which is on either side of it,” Yates said. “The correlation is that it creates the right environment here to grow healthy, strong saffron.” And once an array’s functional lifetime is up, it can be removed, and the field underneath is ready for agricultural use.
The final verdict on the viability of solar-plus-saffron won’t be determined until the two-year test is complete. Yates has theories as to why the yield was stronger under the panels—partial shading, controlled water run-off—but nothing is definitive yet.
The most eagerly anticipated answer of this last year’s testing is how the saffron fares through the winter under the panels.
“In the future, I think if universities, or agricultural R&D sections, have cooperation with solar technologies or farms, we can think about designing the solar farm based on agricultural things,” said UVM agroecologist Arash Ghalehgolabbehbahani. “We have to think about increasing the quality of soil for producing crops in the solar farms, and we have to have a clear approach for that.”
Legal hurdles on farmland
Vermont ranked third for total state solar power generation, accounting for about 11% of the state’s energy, and has the most solar jobs per capita. Yates said it’s a progressive solar state, but it has still encountered setbacks.
Saffron’s stigma must be harvested and dried on sunny mornings. The red tendrils are traded globally for thousands of dollars per pound. University of Vermont
State legislation requires net-metered projects to be built on designated sites. Net-metered solar projects can only be installed on greenfields if the array is between 150 and 500 kW, and if it is installed on land for agricultural use, the farm facilities must offtake at least 50% of an array’s power production.
“For a lot of developers and installers, it’s quite a blow, because that was a large portion of what we do in helping the farmer stay on their land [with solar leases],” Yates said. “We sought to find an alternative way to change the story.”
Farms lease land to solar arrays and commonly distribute the energy elsewhere. Yates hopes the findings of this study catch the attention of state legislators, making them reconsider the limitations current legislation enforces on green field and agricultural sites.
“There is no path saying if we grow saffron then we can do something,” Yates said. “It’s more a matter of trying to figure out a way to create a product that is more valuable that can change the way people think about solar and fields.”
Lots of options these days in “agrivoltaics.” In Vermont, we call it “farming-friendly solar.”
Option low growth tubers (like sweet potato) would yield much more produce …even if hand harvested.
What a super cool article.