The following article by The National Renewable Energy Laboratory – summary by Kari Lydersen via Energy News Network – demonstrates mixed and sometimes puzzling results, indicating researchers need more time and resources to figure out how to maximise agrivoltaics’ potential. This is part two of a two-part article.
Part 1 of this article showed that recent analysis had revealed a daunting number of variables that need to be considered when attempting to pair agricultural production and solar generation.
It also showed that US federal researchers know that solar panels and crops can coexist and provide mutual benefits in certain scenarios. A recent study by the National Renewable Energy Laboratory (NREL) confirms this but also shows that such co-location can lead to crop or financial losses, including from complications like mold-causing dew accumulation and soil damage from construction equipment.
InSPIRE sites including in Minnesota are exploring the performance of different seed mixtures, hydrologies and soil conditions. Planting pollinator habitats under and around solar panels is meant to benefit nearby farmland. But the study notes there can be diminishing returns with larger pollinator-habitat projects as pollinators in the middle of the site may not travel out to surrounding fields.
Research challenges
While continued research is crucial to scaling up and expanding agrivoltaics successfully, the research itself presents many challenges.
Many crops grow in cycles of three years or more, so a long time is needed to measure yields. In addition, soil and water conditions can vary greatly even in one plot, not to mention between plots, making standardised comparisons difficult. Since research will generally be happening on active farms, the scientific process needs to accommodate the needs of farmers.
“Often, research activities must accommodate the realities of farm operations,” the study says. “This might mean harvesting more frequently or on different days than planned based on when crops are ripe, or adjusting activities in anticipation of a coming frost.”
Byron Kominek moved back to his family farm in Colorado after working in international development in Africa. His farm became the site of Jack’s Solar Garden, the nation’s largest agrivoltaic research site. He’s collaborated with researchers and seen both the promise and the greatly varying results of agrivoltaics.
“I’m not a professional researcher – my level of research will be a bit messier than the folks from academia who are far more rigid with what they do,” he noted. “It’s fun to learn from them, and I share back what I’ve heard from other researchers in the field or observations I’ve been making as I spend a considerable amount of time here myself.”
Kominek has been especially focused on herbs like lemon balm, peppermint and sweet grass.
“There’s a drastic difference in the quality of the lemon balm, and how much we can pull off each plant in rows that get different amounts of sun based on their placement. It dries out and is smaller, with not as good flavour growing outside the solar array as opposed to under the panels.
“These [herbs] are perennial plants, so it will take some years to get to their maximal extent,” Kominek said. “We’re playing with getting that anecdotal evidence, but if we had someone who wanted to actually fund us, and spend more time figuring it out — that would be helpful.”
The life of a solar installation is 20 to 30 years, longer than most studies continue, yet conditions and performance could change significantly over this time frame. NREL notes that both field research and modeling should be used to predict agrivoltaic outcomes.
NREL also notes that “projects change developers or operators throughout the solar development and permitting process, meaning that decisions can be made by entities that are not going to be operating the site over the long term. If agrivoltaics projects cannot be built and operated successfully over the long term, then the validity of the research on these systems will be jeopardised and/or made less relevant.”
Researchers emphasise that agrivoltaics may not ultimately be well suited to all agricultural situations, but the potential especially for vulnerable and diverse communities in the US and worldwide should be prioritised, in research and deployment.
“Some people who are more glass-half-empty will say, ‘Isn’t this a limited solution,’” said Barron-Gafford. “But in places like Kenya, Israel and Northern Arizona where tribal nations are, people would greatly benefit from being able to grow food by dialing back that water stress and allowing them to have renewable energy for water pumping. That’s the scale that will help rural and tribal communities; we don’t need to focus all our efforts on large projects.”