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Semitransparent solar cells could power tomorrow’s self-sustaining greenhouses

Most people understand the broad principles of a greenhouse: A greenhouse is a building with a glass roof and walls, used to grow plants like tomatoes and tropical flowers. The greenhouse stays warm inside, even during night and the winter. That’s because the glass walls of the greenhouse trap the sun’s heat inside. So far, so great.

But what if greenhouses could be used not just to help plants grow, but also to capture light at wavelengths that plants don’t use — all thanks to some smart semitransparent solar panels built into the greenhouse walls themselves. Among other uses, these could help to make large commercial greenhouses entirely self-sufficient.

“[With our work, we have investigated] the ability of semitransparent organic solar cells, integrated onto a greenhouse structure, as a way to mitigate part of the greenhouse energy demand, while having minimal impact on plant growth,” Eshwar Ravishankar, a PhD candidate in mechanical engineering at North Carolina State University, told Digital Trends.

Organic solar cells are a promising alternative to traditional solar cell photovoltaics. They are made of thin translucent film, less than 100 nanometers thick, composed of organic semiconductor materials. They can be fine-tuned to absorb specific wavelengths of light. The fact that they allow much of the light to pass through also makes them perfect for applications such as greenhouses. The same is true of the thin and lightweight solar modules, which could be easily integrated into a greenhouse structure.

“We are now conducting experiments looking at plant growth under these semitransparent solar cells,” Brendan O’Connor, associate professor of mechanical and aerospace engineering at NC State, told Digital Trends. “Preliminarily we are seeing promising results [where], for some plants, there is no observable negative impact. We hope to commercialize this technology. Currently, there are several organic solar cell companies, although there has yet to be wide adoption of this technology. We believe greenhouses provide a natural application that exploits the unique attributes of organic solar cells that other solar cell technologies cannot achieve.”

In their initial modeling, the researchers have found that it is possible to achieve net-zero energy greenhouse operation in moderate-to-hot climates using the cells. While those energy needs are not met entirely in cooler climates, there is nonetheless a significant reduction in the energy demand for these facilities.

A paper describing the work was recently published in the journal Joule.

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