Broccoli finished late under magenta solar panels in a Swedish field trial, but it finished the same size. Plants beneath the semi-transparent panels needed 25 more days to mature than plants in a fully sun-exposed control plot, and their yield matched the control’s, according to a study from Mälardalen University led by Silvia Ma Lu and published in Cell Reports Physical Science.
The deal on offer is a delayed harvest and a smaller electricity haul in exchange for farming and generating power on the same patch of ground. Ma Lu’s team measured both sides of that bargain, and the numbers on the power side are the harder ones to wave away.
Magenta glass and the red-blue filter
Chlorophyll absorbs red and blue light most readily and reflects much of the green, so a magenta filter that holds back green and passes red and blue spares the wavelengths a leaf uses best. ScienceAlert reports that the panels pass those wavelengths to the crop, and a summary of the university’s release says the color was chosen to boost the blue and red light plants use most heavily for photosynthesis.
The problem the color addresses is the standard objection to agrivoltaics. Opaque panels block most of the light beneath them, so a farmer who installs them gives up crop area, and a crop grown under shade usually pays for it. Letting the useful wavelengths through is meant to keep the plants working while the cells take the rest. ScienceAlert’s headline calls the panels rose-tinted, while the university’s release describes them as magenta; both refer to the same filtered cells. The 2026 trial is a test of how far that works with a real vegetable, grown to harvest, rather than a measurement of light levels alone.
Ma Lu’s earlier work approached the same problem from the modeling side. Her 2024 licentiate thesis at Mälardalen, described on the university’s calendar, dealt with how photosynthetically active radiation behaves inside agrivoltaic systems, meaning setups that combine solar generation with cultivation, and with how the reflectivity of a growing crop changes the predictions.
Two panel systems against a control
The experiment ran during the 2024 growing season at a farm site in Sweden. The researchers built two systems, each 20 meters by 20 meters, from semi-transparent magenta panels, and left a third plot uncovered as the control, according to the same release summary. One system let through 50 percent of the light and the other 70 percent.
The delay is measured against that open plot. Popular Science reports that broccoli beneath the panels took 25 days longer to mature than traditionally exposed plants, though the final heads matched those of conventionally grown broccoli. The coverage describes the delay for broccoli under the panels in general. It gives no separate figure for the 50 percent and 70 percent systems, and the researchers noted that the crop performed similarly under both despite their different transparency.
What the shade bought was efficiency. Plants under the 50-percent-transparent panels used the light they received 4.5 times as efficiently, and those under the 70-percent panels 2.8 times as efficiently, ScienceAlert says. Those ratios follow from a simple fact: yield held roughly level while the light reaching the plants fell, so each unit of light that did arrive was converted into more crop. The team tracked photosynthesis, nutrient composition, yield, air temperature, humidity and soil moisture across all three plots.
ScienceAlert adds that the researchers see the prototypes as a fit for community gardens and greenhouse roofs, with further optimization and validation across seasons still ahead. A single growing season at one site cannot show how the 25-day lag would behave in other years or climates, and the coverage reports no repeat trial.
The electricity given up
The magenta cells generated about 224.7 megawatt-hours per hectare over the growing period, roughly 100 megawatt-hours less than conventional panels would have produced on the same area, as ScienceAlert reports. By that arithmetic, a conventional array would have made about 325 megawatt-hours, so the magenta panels delivered a little under 70 percent of it. Another write-up of the study quotes Ma Lu on the principle: the panels use part of the incoming sunlight to generate renewable electricity while letting part pass through to the crops below.
Ramesh Rayudu, an expert quoted in the ScienceAlert piece, noted that the shortfall would take 1.2 to 3.2 tonnes of additional broccoli per hectare to offset in value. Ma Lu was cautious about scale. She said the configuration may suit smaller applications such as community gardens or greenhouse roofs rather than immediate deployment over large agricultural areas.
The trial covers one growing season at one Swedish site, and Rayudu’s range is the figure the extra harvest value has to meet for the 25-day wait to pay for the roughly 100 megawatt-hours the panels give up.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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