A recent analysis reveals the daunting number of variables that must be considered when attempting to link agricultural production and solar energy.
Federal scientists know that solar panels and crops can coexist and provide mutual benefits in certain scenarios. A recent study from the National Renewable Energy Laboratory (NREL) confirms this, but also shows that such co-location can lead to crop or economic losses, including from complications such as mold-causing dew accumulation and soil damage from construction equipment.
Advocates who see the concept as a potential solution to land-use constraints are now pushing for more funding and collaboration with farmers to test and document results in as many different settings as possible. The hope is that they can prove benefits in enough scenarios to help the solution scale beyond the handful of small farms that currently implement it.
“We know we can grow food under solar projects,” said the NREL paper’s lead author, Jordan Macknick. “What remains to be seen is whether we can scale up agrivoltaics in a way that meaningfully improves local food production and farmers’ bottom lines, while being consistent with the realities of solar development costs, timelines and practices.”
Moisture and soil
NREL defines agrivoltaics as “the sharing of sunlight between the two energy conversion systems: photovoltaics and photosynthesis,” noting that “the solar and agricultural activities [must] influence each other. On the same subject : How a few geothermal plants could solve America’s lithium supply crunch.”
Agrivoltaics includes planting pollinator habitat in and around solar panels, and allowing animals to graze around panels. But the sector with the most variables to study is undoubtedly the cultivation of crops under and between solar panels.
In 2015, the US Department of Energy began researching agrivoltaics through the InSPIRE (Innovative Solar Practices Integrated with Rural Economies and Ecosystems) program. The August NREL paper compiles results from InSPIRE sites with universities and other partners in states including Arizona, Georgia, New York, Minnesota, Colorado, Idaho, Oregon, California, Pennsylvania, Massachusetts and Washington, D.C.
The analysis confirmed that agrivoltaics can help in water-stressed areas, since the shade from panels reduces evaporation due to sun and wind, and water from rainfall or even water used to clean panels can be collected and directed to crops. Electricity generated can also be used on site to power pumps for irrigation. At a “dry farming” test site in Oregon’s Willamette Valley, researchers are investigating whether agrivoltaics minimizes a condition in tomatoes known as drought-exacerbated blossom rot.
However, increased moisture retention from solar panels can also create complications. Rodents and insects may be attracted to moisture and humidity, the study notes; rodents can damage crops and also chew through electrical wires. At Jack’s Solar Garden in Colorado, fungus grew where runoff from dew on the panels collected. Researchers noted that problems could be averted by moving beds away from the drip, or otherwise managing dew collection.
Greg Barron-Gafford, a geography professor and director of food, water and energy research at the University of Arizona’s Biosphere 2, noted that despite some of the challenges, increased moisture under panels is generally a boon for plants.
“If a plant is in a more humid environment, it’s less stressed about conserving water, and it can do more photosynthesis,” he said. That means more growth of leafy greens like kale and lettuce, and more resources extracted from the leaves for fruit plants like peppers.
Building agrivoltaics – with heavy equipment – can compact soil, making it harder for it to retain water and nutrients. InSPIRE research in Colorado showed that soil at agrivoltaic sites is still compacted a decade after construction. But the use of certain types of equipment and construction processes can reduce the impact on soil. University of Maine researchers are studying whether “cautious” or “mindful” low-impact construction practices can improve agrivoltaic blueberry yields.
Understanding the local soil variation and quality can help minimize damage. Examining the past use of the land, including the use of herbicides and pesticides and the types of crops grown, also helps in designing successful agricultural projects.
Mixed results
The performance of certain crops can be counterintuitive, emphasizing the need for evidence-based research, the NREL study notes. For example, in Colorado, “sun-loving” grasses outperformed “shade-loving” grasses in the shade of solar panels, surprisingly. This may interest you : What does solar energy means ?. In addition, some crops must be rotated after several seasons due to their effect on the soil, so an agrivoltaic matrix must be planned for several seasons.
The study aggregates the effects of agrivoltaics on crops in different locations. Tomatoes saw up to double yield with agrivoltaics, while wheat, cucumbers, potatoes and lettuce showed significant negative effects and maize and grapes had minimal impact.
In areas that do not experience extreme sun or heat, reduced yields may be due to reducing the amount of sunlight that plants receive under panels. These realities must be considered, but there are also ways to moderate the sun-blocking influence, say researchers.
Tracking solar panels that move with the sun only shade plants for part of the day. And Barron-Gafford noted that advanced technology including solar panels can allow the wavelengths of light that plants need most to pass through, while blocking and generating energy from light rays that are less useful to plants.
Pollinator habitat planted under solar panels is perhaps the most widely used type of agrivoltaics currently, with some states including Illinois and Minnesota offering incentives for solar projects for pollinator habitat. Research is also moving forward on this front, with more research needed to evaluate the effectiveness of the pollinator habitat, and the extent to which it is maintained over several years.
InSPIRE sites, including in Minnesota, explore the performance of different seed mixes, hydrologies and soil conditions. Planting pollinator habitat under and around solar panels is intended to benefit nearby farmland. But the study notes that there may be diminishing returns with larger pollinator habitat projects, as mid-site pollinators 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 the yield. And soil and water conditions can vary widely even within one plot, not to mention between plots, making standardized comparisons difficult. Since research will generally take place on active farms, the scientific process must meet the farmers’ needs.
“Often, research activities have to be adapted to the realities of farming,” the study says. “This may mean harvesting more often or on different days than planned based on when crops are ripe, or adjusting activities in anticipation of an upcoming 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 country’s largest agrivoltaic research site. He has collaborated with researchers and seen both the promise and the highly variable results of agrivoltaics.
“I’m not a professional researcher – my level of research will be a bit messier than people from academia who are far more rigid about 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 made as I spend a lot of time here myself.”
Kominek has been particularly focused on herbs such as lemon balm, peppermint and sweet grass.
“There’s a drastic difference in the quality of the lemon balm, and how much we can pull from each plant” in rows that get different amounts of sun based on location. “It dries out and is smaller, with not as good a taste” growing outside the solar panel as opposed to under the panels.
“These [herbs] are perennial plants, so it will take a few years to reach their maximum extent,” Kominek said. “We’re toying with getting the anecdotal evidence, but if we had someone who actually wanted to fund us, and spend more time figuring it out — that would be helpful.”
The lifespan of a solar installation is 20 to 30 years, longer than most studies continue, but conditions and performance can change significantly over that 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 decisions may be made by entities that will not operate the site in the long term. If agrovoltaic projects cannot be successfully built and operated over the long term, the validity of the research on these systems will be jeopardized and/or made less relevant.”
Researchers emphasize that ultimately agrivoltaics may not be well-suited for all agricultural situations, but the potential especially for vulnerable and diverse communities in the United States and around the world should be prioritized, in research and deployment.
“Some people who are more glass-half-empty will say, ‘Isn’t this a limited solution,'” Barron-Gafford said. “But in places like Kenya, Israel, northern Arizona where tribal nations are, people will benefit greatly from being able to grow food by reversing water stress and allowing them to have renewable energy for water pumping. It’s the scale that will help rural and tribal communities; we don’t need to focus all our efforts on big projects.”
Questions or comments about this article? Contact us at editor@energynews.us.
What are the environmental impacts of using solar energy?
As a renewable energy source, solar energy plays an important role in reducing greenhouse gas emissions and mitigating climate change, which is essential to protect people, wildlife and ecosystems. Solar energy can also improve air quality and reduce water use from energy production.
What are 2 negative effects of solar energy use on the environment? As with the development of any large-scale industrial facility, the construction of solar power plants can pose a risk to air quality. Such threats include the release of soil-borne pathogens and result in an increase in airborne particles that have the effect of contaminating water reservoirs.
What are 10 disadvantages of solar energy?
10 disadvantages of solar panels
- High upfront costs. …
- The size of the system depends on the available space. …
- Requires sunny weather to work best. …
- Production of solar panels can harm the environment. …
- Low energy conversion rate. …
- Cannot be used at night. …
- Solar panels are fixed in their installed location.
What is the biggest problem with solar energy?
One of the biggest problems with solar energy technology is that energy is only generated while the sun is shining. This means that night and cloudy days can interrupt the supply.
What are disadvantages of solar energy?
High initial cost of material and installation and long ROI (but with the reduction in the cost of solar in the last 10 years, solar is becoming more cost effective every day) Needs a lot of space as the efficiency is not 100% yet. No solar power at night so a large battery bank is needed.
Does solar energy have a negative impact on the environment?
Solar energy technologies and power plants do not produce air pollution or greenhouse gases during operation. The use of solar energy can have a positive, indirect effect on the environment when solar energy replaces or reduces the use of other energy sources that have greater effects on the environment.
How much solar energy is needed to power the world?
How many solar panels are needed to power the world? It would take 51.4 billion 350W solar panels to power the world! Put another way, this is the equivalent of a solar power plant covering 115,625 square kilometers.
How much solar energy do we need to power the world? “How many solar panels can power the world? 23 billion solar panels. That’s how many we need.†(Of course, the world will never be 100% solar-powered. Other sources, such as wind power and hydropower, have big roles to play.
Can solar power run the world?
Now, an international team of researchers has determined that if all available rooftops were equipped with solar panels, they could generate enough electricity to power the world.
Is it possible to power the world with solar?
“If we cover an area of the Earth 335 kilometers by 335 kilometers with solar panels, even with moderate efficiencies that can easily be achieved today, it will provide more than 17.4 TW of power. This area is 43,000 square kilometers.
Can the world run on 100% renewable energy?
Without a doubt, renewable energy is the only energy system that is viable in the long term. Coal, petroleum and wood, which were the most important sources of energy, are not renewable resources. These resources are not long lasting.
How much solar would you need to power the world?
In total, we would need approximately 1.1 million square kilometers of solar panels to power the entire Earth, less than the area of South Africa.
How many solar panels would it take to power the entire country?
That’s how much electricity solar panels must produce every hour for the entire United States. Therefore, about 7.85 billion individual solar panels, each producing about 350W per hour, are needed to power the entire United States.
Can solar panels power a whole country?
Solar’s abundance and potential throughout the United States is staggering: PV panels on just 22,000 square miles of the nation’s total land area—roughly the size of Lake Michigan—could supply enough electricity to power the entire United States.
How many solar panels does the United States need?
The average American home needs between 16 and 20 solar panels based on average electricity usage of 893 kilowatt hours (kWh) per month. Installing that many solar panels would cost between $12,000 and $17,000 after the federal solar tax.
How many acres of solar panels would it take to power the United States?
Given that the US uses about 4 petawatt hours of electricity per year, we would need about 13,600,000 acres or 21,250 square kilometers of solar panels to meet the US’s total electricity needs for a year. The yellow square is approximately 21,000 square kilometers. Map courtesy of Google Maps.
What city has the most solar energy?
The 5 US cities that produce the most solar energy
- Honolulu, Hawaii.
- Las Vegas, Nevada.
- San Diego, California.
- Albuquerque, New Mexico.
- San Jose, California.
Which city uses the most renewable energy? Honolulu leads the U.S. in solar energy per capita among the cities surveyed, followed by San Diego, Albuquerque, San Jose and Burlington, Vermont.
What is the biggest problem with solar energy?
One of the biggest problems with solar energy technology is that energy is only generated while the sun is shining. This means that night and cloudy days can interrupt the supply.