Agrovoltaics – use land to grow food and hosting solar panels at the same time – seems like such a good idea you might wonder why it’s not used more often. It can increase yields and generate additional income for farmers. However, not all plants thrive while sharing space with solar panels. For example, potatoes, wheat, cucumbers and lettuce don’t fare well, but tomatoes often thrive.
A research paper published by the National Renewable Energy Laboratory in August examined agrivoltaic research across America. It noted that tomato yields doubled on average compared to non-agrivoltaic locations. The NREL found that there are 5 characteristics that determine whether agrovoltaic energy is feasible in a given situation.
- Climate, soil and environmental conditions: The environmental conditions and factors of the specific location that are beyond the control of solar energy owners, solar operators, agrivoltaic practitioners and researchers.
- Configurations, solar technologies and designs: The choice of solar technology, site layout and other infrastructure that can affect light availability and solar power generation.
- Crop selection and cultivation methods, seed and vegetation design, and Management approaches: The methods, vegetation and agricultural approaches used for agrivoltaic activities and research.
- Compatibility and flexibility: The compatibility of solar technology design and configuration with the competitive needs of solar energy owners, solar operators, agronomists and researchers.
- Cooperation and partnerships: Appointments and arrangements made about stakeholders and sectors to support agrivoltaic installations.
Agrivoltaics, extreme heat and drought
Tomatoes are a billion dollar industry in America. California produces the most tomatoes, with Florida in second place. But California is experiencing severe drought and heat due to climate change affecting the agricultural industry. Those factors have led to a shortage of so-called processing tomatoes, which are typically used to make sauces and ketchup.
Drought and extreme heat in California’s Central Valley have led to shortage of tomatoes, especially processing tomatoes, and those conditions are only expected to get worse with climate change. Shade provided by solar panels can help conserve water, create humidity and lower temperatures that can become too hot even for heat-loving tomatoes. Canarian media reports.
If it is too hot, tomatoes will abort fruit development from flowers, as the plant senses that the fruit will not bloom. Solar panels cool the air enough to prevent this process, according to research. And especially in a place like California, where the vast majority of the tomatoes are grown in the country, solar panels can significantly reduce the need for irrigation.
At the University of Arizona Biosphere 2cherry tomatoes doubled their yield when grown under solar panels, as noted in a 2019 study published in Nature Sustainability. “They got a lot of light, a lot of water, and the temperature stress was brought just below that threshold, so they could fruit all summer long and get an extra month of production, and more production per plant,” said Greg Barron-Gafford, lead author of the article and professor at the University of Arizona.
The Arizona study found that solar panels not only cool the air during the day, but also heat the air at night — a benefit for tomatoes and other crops in desert climates like Central California and Arizona, where temperatures can drop after the sun goes down.
The tomato plants also benefited the solar panels. They become less efficient at generating energy when they are particularly hot. The plants growing under the panels provide a cooling effect on the panels through their transpiration.
Practical Considerations For Agrivoltaics
Tomatoes often grow to be about five feet tall, so they fit under solar panels raised up to six feet—higher than most commercial arrays, but standard for agricultural voltaics. Tomatoes are often harvested by hand, and research in Arizona found that agrivoltaic farming could benefit farm workers. Preliminary research showed that skin temperature could be that high 18º F lower work in the shade of panels.
While processing tomatoes are grown in vast fields, many whole tomatoes sold in stores are grown in greenhouses. Researchers said growing tomatoes under solar panels could mimic the conditions of a greenhouse in some climates, and energy from solar panels could also power greenhouses on site.
The adoption of agrivoltaic technology by the tomato industry largely depends on meeting the needs of solar energy developers and growers alike. Raising solar panels to place tomatoes underneath them means extra expense, and machines used on many large farms to pick and plant tomatoes may not work with solar panels.
Research in the state of Oregon
Researchers at Oregon State University investigated tomato cultivation with agrivoltaic cells in a cooler climate for a 2021 study. They found mixed results that support the idea that tomatoes are ideal agrivoltaic candidates in warm climates where most commercial production takes place, but are not suitable for small farmers in cooler climates. The researchers placed some tomatoes under solar panels, others between solar panels and a control group in an open field. Other research suggests that vertical mounting of solar panels is possible increase yield of a solar panel.
Soil and air temperatures were significantly lower in the plots below the panels compared to the plots between the rows and the control field. The soil temperature under the panels was a full 5ºC lower than the intermediate rows and the control. The sunnier control plot yielded the most fruit, but also consumed significantly more water than the other plots, even in a relatively cool climate – an effect that could be amplified in a warmer location.
The researchers concluded that agrovoltaics offered the opportunity to“exchange a reduction in yields for a reduction in water consumption.” The study notes that using water more efficiently may not matter in a high-rainfall place like western Oregon or Florida, but“could be critical in areas that are currently under water stress and are expected to become even more water stressed in the coming years.”
The takeaway meals
Agrivoltaics can benefit farmers who grow certain crops in certain locations. The importance of Research is to determine when and where solar panels and agriculture can help each other. Farmers are very sensitive to productivity and profitability. Particularly in places experiencing drought and rising temperatures during the growing season, the application of agrivoltaic technology could give some farmers the edge they need to survive in a world where climate change is putting traditional farming practices under pressure.
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