With a new photovoltaic panel, researchers harness sunshine to harvest energy and food together, taking advantage of the full light spectrum, and providing a potential win win for farmers.
Arable land is at an all-time premium. Since the last ice age, humans have cleared one-third of the earth’s forests and two-thirds of its wild grasslands, much of it for agriculture. And as the world population - 8 billion as of last November - continues to expand, there’s ever-increasing pressure on farmland to produce not only more food but also clean energy.
A recent study from the University of California, Davis, shows how farmers may soon be able to harvest crops and energy together, on common ground. Researchers concluded that bands within the visible light spectrum can be filtered and harnessed separately - blue light waves to generate solar power and red light waves to grow fruits and vegetables - to make maximum use of farmland, all while lowering heat stress and reducing crop waste.
Photons, or the particles that make up light, have different properties: Blue ones have higher energy than their red counterparts, resulting in light with shorter wavelength and higher frequency. While that gives blue light the jolt needed to generate power, “From a plant perspective, red photons are the efficient ones,” says Abou Najm, an associate professor in the Department of Land, Air and Water Resources at UC Davis and an Institute of the Environment fellow, who co-wrote the paper, adding that red photons "don’t make the plant feel hot.” Thus providing the additional benefit of requiring less water.
While their research was inspired by hydroponic light applications used in indoor farming systems, “those come at a high energy cost,” says Abou Najm. “We decided to use sunlight as our input.”
One of the main goals of the study, he says, is “to motivate the industry to create a new generation of solar panels.” The researchers see potential in organic solar cells, which, unlike the shiny, metallic, silicon-based surfaces, are derived from carbon-based compounds. Thin and translucent, the cells are applied like a film onto various surfaces, including glass. This technology could be used to develop photo-selective PV panels that filter blue light to generate power, while passing the beneficial red spectrum on to crops planted directly below.
For countries and regions facing a tight squeeze on farmland, such increased productivity is even more valuable; especially given that generating clean energy requires 10 times more land per unit of power than fossil fuels.
By maximizing the solar spectrum, “we’re optimizing an endlessly sustainable resource. If a technology kicks in that can develop these panels, then the sky is the limit on how optimized we can be.”
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