The United States dominated the global solar industry in the years following the space race of the 1950s, only to lose ground to overseas competitors by the end of the 20th century. Now the emerging field of agrivoltaics is presenting solar innovators in the U.S. with new opportunities to build their business, while also enabling farmers to take advantage of new clean energy systems that can co-exist with crops and livestock.
New solar technology is expanding opportunities for farmers
In the early 2000s, solar development on farmland typically meant taking the land out of production. With cost-cutting in mind, solar panels were placed just about a foot above the ground in large, tightly-spaced arrays, providing no opportunity for farming.
Agrivoltaics represents a more holistic approach to land use, in which solar panels are typically placed 10 to 16 feet high and spaced farther apart. Though the extra racking adds expense, that is counterbalanced by the farmer’s ability to continue farm operations within the solar array.
To date, much of the agrivoltaics development in the U.S. involves conventional silicon solar panels, with a focus on establishing pollinator habitats or grazing livestock.
More recently, new solar technologies are expanding the options for growing food crops, including greenhouse crops. One example in that area is a new type of film, developed by the manufacturing company 3M and the Swiss technology firm Voltairs, which can harvest energy while enabling sufficient light to get through the greenhouse walls for the crops to grow.
Bifacial technology is also emerging in agrivoltaics. In contrast to conventional solar panels, bifacial solar panels harvest energy from both sides. That means the panels can be placed vertically instead of tilted at an angle, saving considerable space within a field. Farmers can also deploy the vertical panels as fencing around a field, saving even more space.
In addition, bifacial panels provide a sheltering environment that can enhance crop growth, potentially creating new market opportunities for farmers. At the University of Vermont, for example, researchers are assessing the use of bifacial solar panels to support saffron as a high-value specialty crop for farmers in the Northeast.
Bringing space solar back down to Earth
Bifacial solar panels deploy the same type of silicon solar cells used in conventional solar panels around the world. Another approach is represented by the U.S. firm Ascent Solar, which specializes in CIGS solar cell technology for space applications. Now the company aims to put that same technology to work on farms.
CIGS stands for the materials copper, indium, gallium, and selenide, which are combined in a thin film to create solar cells. Thin film solar cells are not as efficient at converting light into energy as silicon, but they are flexible and lightweight. They can be deployed over a wide range of use cases where silicon panels are too heavy and rigid.
TriplePundit spoke with Ascent Solar CEO Paul Warley for some insight on the opportunities to use the company’s CIGS technology in agrivoltaic projects. He explained that building up the efficiency of CIGS technology was the key development that allowed Ascent to pursue the agrivoltaics market.
“We went from 6 to 7 volts per panel to 14.5 volts per panel, and that gave us the groundwork to start looking at this,” he said.
Warley also described how the light weight and flexibility of CIGS film offers the opportunity to develop new agrivoltaic designs that expand the space available for farming.
“Our product … can be mounted on inexpensive metal like tin, which can be slightly rolled or curved,” Warley explained. The curvature enables the panel to harvest more sunlight at different times of the day.
Partly due to their lighter weight, CIGS solar panels can be raised 20 feet off the ground. The panels are also spaced 15 to 28 inches apart, to allow more room for sunlight to reach the crops below.
The CIGS array allows for 95 percent or more of the land under the solar panels to be used for growing crops, Warley said. In contrast, he notes that conventional agrivoltaics arrays leave just 40 to 50 percent of the land underneath with enough sunlight to grow crops efficiently.
Warley also estimates that Ascent’s technology can reduce the amount of water needed for irrigation by 15 to 20 percent. That is consistent with research findings, which show that the partial shade thrown by agrivoltaic arrays helps prevent moisture loss in soil.
Next steps for CIGS in agrivoltaics
Warley foresees demand for CIGS agrivoltaics arrays in water-thirsty agricultural operations like almond farms, where height is also an important element. A typical almond tree stands about 10 to 15 feet high, with a range of up to 20 feet.
For the present, Ascent Solar is focusing on an agrivoltaics grant application to the U.S. Department of Energy, to install its CIGS solar panels at a vineyard in California. The project will help the grower manage the high cost of both water and electricity in the state, Warley said.
In addition to providing zero-emission electricity for the barn and other structures at the vineyard, the panels could also help create a microclimate to buffer the grape vines against the impacts of climate change.
Similar projects are already underway in other parts of the world. The European energy firm Iberdrola, for example, is assessing the use of conventional solar panels in a small agrivoltaic project at a vineyard in Spain. The European energy firms Enel Green Power and EDF Energy are also exploring the use of solar panels in European vineyards.
That trend has yet to gain momentum in the U.S., though some grape growers have installed conventional on-site solar arrays on rooftops and other non-growing areas.
If and when U.S. grape growers and other farmers are ready to explore agrivoltiacs, they may be able to take advantage of CIGS technology for interior facilities as well as cropland.
Last week, Ascent announced that it’s working with the University of Stuttgart to develop new prototype solar arrays for the school’s Institute for Building Energetics, Thermotechnology and Energy Storage, which focuses on sustainable engineering for living and working spaces.