Planting broccoli under magenta solar panels helped the plants absorb sunlight more efficiently than those grown out in the open finds a study publishing October 2 in the Cell Press journal Cell Reports Physical Science. Scientists used customized, semi-transparent solar panels to generate electricity while boosting blue- and red-light wavelengths to enhance broccoli growth. The crops grown with these panels showed a 4.5-fold increase in how efficiently they used sunlight and ultimately grew as large as traditional broccoli, although it took them 25 days longer to mature. The solar panels offer a potential tool for farmers to harvest renewable energy while sustaining crop yields.
"The basic concept is quite straightforward," says author Silvia Ma Lu of Mälardalen University in Västerås, Sweden. "The solar panels use part of the incoming sunlight to generate renewable electricity while allowing part of the light to pass through to the crops growing underneath. The broader goal is to investigate whether sunlight can be used more efficiently by allocating different portions of the solar spectrum to crop growth and electricity generation."
Using conventional solar panels on farm fields allows farmers to produce renewable electricity on land where ample space is already available while protecting plants from exposure to too much sunlight and extreme weather such as hail or heavy rainfall. However, since conventional dark-blue panels are typically opaque, they can create too much shade, reducing some crops' yields—which semi-transparent and colored panels can help mitigate.
"There is no single agrivoltaic design that will work optimally everywhere," says Ma Lu. "More research is needed to understand how different crops respond to different system configurations and climatic conditions and to design systems that balance agricultural production with renewable electricity generation."
To advance this research, Ma Lu and colleagues chose to focus on broccoli, a highly nutritious crop popular worldwide and well suited to the climate of their experimental site on a farm in Sweden. The researchers built two 20-meter by 20-meter systems made from semi-transparent, magenta-colored solar panels with different levels of transparency, allowing varying amounts of sunlight to reach the plants cultivated beneath. In a third plot of land, broccoli plants were fully exposed to the sun.
Throughout the 2024 growing season, the team compared the broccoli in each plot, monitoring environmental conditions including air temperature, relative humidity, and soil moisture as well as crop yield, nutrient composition, and how well the plants performed photosynthesis.
"One of the most interesting findings was how similarly the broccoli performed under the two solar panel systems despite their different transparency levels," says Ma Lu, noting that solar panels with a greater density of photovoltaic cells can produce more electricity. "However, these findings are specific to our experimental conditions and should be validated across additional growing seasons and system configurations."
The systems tested in this study are research prototypes, she added, with more research needed at larger scales and over multiple growing seasons. If the technology were scaled up for commercial use, electricity generated from crops could, in principle, power farm operations such as irrigation, machinery, or cooling and storage systems, or it could be supplied to the electricity grid. This could lower farmers' electricity bills and even give them an additional source of income.
Ma Lu and colleagues have already begun further evaluating the magenta panels, as well as red and blue ones, by testing them in controlled lab settings without interference from light that isn't filtered through the panels.
"Configurations similar to our prototype may currently be suitable for smaller-scale applications, such as community gardens, or for integration into greenhouse roofs rather than immediate deployment over large agricultural areas," says Ma Lu.
