Energy

Transparent solar cells don't steal light from greenhouse crops

Transparent solar cells don't ...
A new study has found that crops can grow in greenhouses with built-in transparent solar cells
A new study has found that crops can grow in greenhouses with built-in transparent solar cells
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A new study has found that crops can grow in greenhouses with built-in transparent solar cells
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A new study has found that crops can grow in greenhouses with built-in transparent solar cells
A diagram of the experimental setup
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A diagram of the experimental setup

Advances in transparent solar cells mean that soon we might be able to install them into windows and greenhouses. But in the latter case, would they deprive plants of vital sunlight? To find out, researchers at North Carolina State University grew lettuce under various wavelengths of light, and found that the plants did just fine.

Organic solar cells are emerging as a viable system for renewable energy, thanks to a number of advantages. They can be more flexible than other technologies, be made transparent or semi-transparent, and the wavelengths of light they harvest can be adjusted.

In theory, that could make them perfect for embedding into greenhouse roofs. There, these organic solar cells could capture certain wavelengths of light while still allowing some of it to pass through to the plants below. In a previous study, the NC State team investigated how much energy this kind of setup could produce, and found that it could be enough to make greenhouses energy neutral.

But of course there’s one big piece of that puzzle missing – nobody asked the plants how it affected them. So that was the focus of the new work.

A diagram of the experimental setup
A diagram of the experimental setup

The researchers grew groups of red leaf lettuce in greenhouses for 30 days, which took them up to full maturity. The different groups were all exposed to the same growing conditions, such as temperature, water, fertilizer and CO2 concentration. The only difference was light.

The lettuces were split into four groups – a control group that received regular white light, and three experimental groups that grew under light passed through different filters. These changed the ratio of red to blue light that they received, to mimic wavelengths that would be blocked by transparent solar cells.

Then the team monitored several markers of plant health, including number and size of leaves, weight, how much CO2 they absorbed and the levels of antioxidants they contained. And perhaps surprisingly, it turns out that the lettuces thrived regardless of what type of light they received.

“Not only did we find no meaningful difference between the control group and the experimental groups, we also didn’t find any significant difference between the different filters,” says Brendan O’Connor, co-corresponding author of the study.

The team says that it’s currently working on testing the effects of blocking different wavelengths of light on other crops, like tomatoes.

The research was published in the journal Cell Reports Physical Science.

Source: North Carolina State University

6 comments
TpPa
If these transparent organic solar cells can still produce viable energy while only harvesting selected wave lengths it could be a game changer for so many applications. I would love to replace all my South windows on my house with windows that allow us to still see clearly through while helping top off our battery bank.
paul314
Experience with grow lights has given researchers a pretty good idea of what wavelengths plants want for best growth -- for plants growing in some greenhouses, absorption of the rest might actually help by reducing heat load.
Daishi
I agree with others that research with grow lights provides a lot of data about what spectrums are useful and which can be captured as a starting point but real-world experiments are still important. Transparent solar panels could also also have a transformative impact in other applications. In a warm climate they could be used to allow visible light in while capturing other spectrums that mostly contribute heat load that must then be air conditioned. You would see benefit of reduced power demand even before accounting for the electricity they produce. I could see buying something like this with other useful features like remotely controlled "smart glass" so instead of manually controlled blinds you could say "google/alexa, dim the windows to 50%" or program the function to be automatic based on time of day.
Ralf Biernacki
This is a useful technology, but I think more applicable to premium home/office windows, until the price of these solar cells comes way down. Sure, they can provide the power to offset running costs, but initial fixed costs would be staggering for any meaningful acreage. Note that even the researchers simulated the effects with filters, rather than glazing the test greenhouses with actual solar cells. Care to guess why? ;-)
niio
NASA does a lot of research on growing plants under artificial light. They say blue and red are most important, green and yellow less so but some is still necessary. The fact that leaves appear green substantiates this, as reflected light cannot be used by the leaf.
Allen
I would like to point out that the "three experimental groups that grew under light passed through different filters. These changed the ratio of red to blue light that they received, to mimic wavelengths that would be blocked by transparent solar cells" So this DID NOT test how lettuce grew under transparent or semitransparent solar cells. The test needs to be with the light passing through actual solar cells to be a true finding.