Semi-Transparent Solar Cells Could Make Greenhouses Self-Sufficient

An anonymous reader quotes a report from New Atlas: Organic solar cells (OSCs) have a few advantages over other designs. They still collect energy from sunlight, but can be made more flexible, transparent (or at least semi-transparent) and can be tuned to only absorb certain wavelengths of light. That potentially makes them perfect for greenhouse roofing -- they can let most light through for the plants, while harvesting enough to offset a decent chunk of the facility's energy needs. "Plants only use some wavelengths of light for photosynthesis, and the idea is to create greenhouses that make energy from that unused light while allowing most of the photosynthetic band of light to pass through," says Brendan O'Connor, corresponding author of the study [from North Carolina State University]. "However, until now it wasn't clear how much energy a greenhouse could capture if it was using these semitransparent, wavelength selective, organic solar cells."

To begin to answer that question, the researchers modeled how much energy would be coming in from a greenhouse with OSCs in the roof, versus the amount of energy it would normally consume. The idea was to find the point where the greenhouse becomes energy neutral -- that is, it generates enough energy from the Sun to completely power itself. For this study, the theoretical greenhouses were modeled on the energy needed to grow tomatoes in three locations with different climates -- Arizona, North Carolina and Wisconsin. As a bonus, the OSCs are effective insulators too, helping maintain the right temperature. The team found that there would be a small hit to the amount of usable light the plants inside would receive, but the benefits would be worth it. In the famously sunny Arizona, for example, a greenhouse with OSCs installed could become energy neutral while blocking just 10 percent of the light the plants need. This shouldn't negatively affect the plants, the team says. In fact, the energy output could be doubled with just a little more light blocked. In North Carolina, sunlight is a little more sparse, so a greenhouse would need to block 20 percent of the photosynthetic light to become energy neutral. Chilly Wisconsin winters would be too much to ever achieve neutrality though, but these greenhouses could still generate almost half of their energy needs. The new study was published in the journal Joule.

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