Colored Solar Panels Let Farms Harvest Crops and Electricity at Once
Farmers who want to add renewable energy to their land have long faced an awkward trade-off: the opaque panels that produce the most electricity also cast the deepest shade. New research suggests that customized, semitransparent solar panels tinted a vivid magenta can split that difference, generating power while steering the most useful portions of the light spectrum toward the crops growing below.
The study, scheduled for publication Oct. 2 in Cell Reports Physical Science, centers on broccoli cultivated beneath the panels at an experimental site at Kärrbo Prästgård farm in Sweden. According to the findings, the broccoli absorbed sunlight more efficiently than plants grown out in the open, and the harvested heads ultimately reached the same size as conventionally grown broccoli — although they required 25 extra days to mature.
The work points to a potential tool for farmers who want to produce renewable electricity without giving up the productivity of the land beneath their arrays.
How the Magenta Panels Work
The underlying concept is straightforward, according to Silvia Ma Lu of Mälardalen University in Västerås, Sweden, an author of the paper. The panels intercept part of the incoming sunlight and convert it into renewable electricity, while allowing the remainder to pass through to the crops underneath. The wider ambition, she explains, is to find out whether sunlight can be used more efficiently by dividing the solar spectrum between two jobs at once: feeding plants and feeding the grid.
Magenta is not an arbitrary aesthetic choice. Instead of blocking light indiscriminately the way an opaque panel does, the semitransparent design filters the solar spectrum so that blue and red wavelengths — the bands plants lean on most heavily — are emphasized for the crop canopy.
- Partial transmission: a share of incoming sunlight passes through the panel to reach the plants.
- Power generation: the light the panel captures is converted into renewable electricity.
- Spectral tuning: blue and red wavelengths are boosted to support crop development.
- Physical shelter: mounting panels over a field can also shield plants from excessive sunlight and from extreme weather such as hail or heavy rainfall.
What the Broccoli Trial Revealed
The researchers focused on broccoli as their test crop, growing it beneath the colored, semitransparent panels at the Swedish experimental site. The headline result was a 4.5-fold increase in how efficiently the plants used the sunlight available to them compared with broccoli grown in the open. In practical terms, that efficiency gain showed up in the harvest: the broccoli produced under the magenta panels grew as large as traditional open-field broccoli.
There was a catch, however. The sheltered plants took 25 days longer to reach maturity than their counterparts in full sun. That delay matters for growers working with tight planting schedules, sequential harvests, or contracts that depend on hitting specific market windows. It also suggests that the light environment beneath the panels, while favorable in spectral terms, is not a perfect substitute for unrestricted sunlight in every respect.
Even so, the combination of a full-sized harvest and on-site electricity generation is the outcome that makes the approach worth pursuing. Rather than asking a field to choose between food and power, the system asks it to do both.
Why Agrivoltaics Is Drawing Interest
Putting conventional solar panels on farmland already offers farmers a way to produce renewable electricity on land that is available and spacious, while simultaneously protecting crops from too much direct sun and from damaging weather. The difficulty is that standard dark-blue photovoltaic panels are typically opaque. Placed above a field, they can create more shade than many crops can tolerate, dragging down yields.
That is precisely the problem that semitransparent and colored panels are designed to soften. By allowing a controlled fraction of light through and shaping which wavelengths make it, they aim to keep electricity production meaningful while leaving enough usable light for the plants below. The Swedish broccoli trial is one data point in that effort, testing whether a magenta filter can be tuned to serve a specific crop rather than simply reducing light across the board.
No Single Design Fits Every Farm
Ma Lu is careful not to oversell the result as a universal recipe. In her view, there is no one agrivoltaic configuration that will perform optimally in every location. What works for broccoli on a Swedish farm may not translate directly to a different crop, a different latitude, or a different climate.
She argues that more research is needed to understand how various crops respond to different system setups and to varying climatic conditions, and to design installations that genuinely balance agricultural production against renewable electricity generation. The goal is not to declare a winner among panel colors or transparency levels, but to build a body of evidence that lets growers match a system to their land, their crop, and their energy goals.
What Still Needs to Be Worked Out
Several open questions remain before colored panels become a routine sight over working farmland. The 25-day maturation gap in broccoli raises the question of how other crops — particularly ones with shorter growing seasons or stricter harvest deadlines — would respond to the same filtered light. The economics of installing semitransparent panels, which typically generate less power per unit area than fully opaque alternatives, will also need to be weighed against the value of the crop protected beneath them.
Researchers also want to know how the systems behave over multiple seasons and across the range of weather conditions that real farms experience, from the hail and heavy rain the panels can help deflect to the cloudier stretches when light is already scarce. Each of those variables can shift the balance between how much electricity a field produces and how much food it yields.
Key Takeaways
- Customized semitransparent magenta solar panels generated electricity while boosting blue and red wavelengths for broccoli growing beneath them at a Swedish experimental site.
- The sheltered broccoli showed a 4.5-fold increase in sunlight use efficiency and grew as large as broccoli raised in the open.
- The trade-off: plants under the panels took 25 days longer to mature.
- Colored, semitransparent panels are being explored as a way to avoid the excessive shading caused by opaque dark-blue panels on farmland.
- The study's authors say no single agrivoltaic design will suit every crop, configuration, or climate, and that further research is required to balance food production with renewable electricity generation.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
