A new breed of solar panel can do double duty on greenhouse roofs by not only generating renewable electricity, but also by using a light-altering dye to help optimize photosynthesis in the plants beneath them.
Normally, putting solar panels on the roof of a greenhouse wouldn't be a bright idea, as the panels would block the sun's rays from hitting the plants, but a spin-off company from UC Santa Cruz has developed a novel technology that lets sunlight through, while also changing its color to enhance plant growth and health. And a recent study confirms that Soliculture's LUMO solar panels, which are said to generate electricity efficiently and at a lower cost than conventional photovoltaic systems, don't negatively affect crop growth, and in fact work to boost yields in some plants and to reduce water usage.
The Soliculture LUMO panels, which are Wavelength-Selective Photovoltaic Systems (WSPVs) that feature narrow photovoltaic strips embedded in a "bright magenta luminescent dye" that can absorb some of the sunlight's blue and green wavelengths while converting some of the green light into red light, which "has the highest efficiency for photosynthesis in plants." One other advantage of WSPVs is their lower cost, which is said to be about 65 cents per watt, or 40% less than conventional solar panels.Michael Loik, a professor of environmental studies at UC Santa Cruz, recently published a paper in the journal Earth's Future that examines the effects on plant physiology from the use of WSPVs, which "represent a new wedge for decarbonizing the food system," and concludes that the technology "should help facilitate development of smart greenhouses that maximize energy and water use efficiency while growing food."
According to Loik, most (80%) of the first crops of plants grown in the magenta-hued solar greenhouses weren't affected at all by being under the spectrum-shifted light of the panels, while 20% "actually grew better." A team led by Loik monitored both the rate of photosynthesis and fruit production in 20 varieties of plants, including tomatoes, cucumbers, strawberries, peppers, basil, lemons, and limes grown in three locations under the magenta greenhouse roofs, and while they couldn't determine why 20% of the plants grew more vigorously, they also noted a 5% savings in water use by tomato plants.
"We have demonstrated that 'smart greenhouses' can capture solar energy for electricity without reducing plant growth, which is pretty exciting." - Loik
Why is this such a big deal? Greenhouses, even though most rely on sunlight to grow the plants within, also use a lot of electricity to run fans, sensors and monitoring equipment, climate control (heat and/or ventilation) and lights, and with greenhouse production increasing by a factor of 6 over the last 20 years, the global energy demands for greenhouses is growing at a rapid pace as well. With systems such as this one in place around the world, it could help make greenhouses self-sustaining, and the technology "has the potential to take greenhouses offline," according to Loik.
According to the Soliculture website, LUMO is "the first commercially available, mass produced Luminescent Solar Collector (LSC)" and greenhouses with the technology installed on them "have been generating power internationally for over 4 years." The payback period is said to be between 3 and 7 years, with a 20+ year electricity-generating life, which could lead to a 20-30% capital cost savings when compared with a conventional greenhouse. The full UC Santa Cruz study referenced above can be accessed here: "Wavelength-Selective Solar Photovoltaic Systems: Powering Greenhouses for Plant Growth at the Food-Energy-Water Nexus."