Greenhouses join plants in the energy conversion business

Meeting the world’s growing food and energy demands while mitigating climate change is one of the greatest challenges of our time. Agriculture and buildings are among the greatest consumers of energy – and consequently, generators of emissions. Although greenhouse farming can significantly increase food production per hectare relative to open field agriculture, it is more energy intensive. But thanks to the large surface areas bathed in the sun’s glow, greenhouses are also in a unique position to take advantage of sunlight to make cleaner electricity – with huge global benefits for farming and the environment. With the EU-funded PanePowerSW project, researchers are bringing their transparent solar glass product, PanePower Solar Window, to market, for everything from greenhouses to commercial building windows.

Boosting energy production in more ways than one

Solar cells convert the sun’s light to electricity by absorbing photons from large regions of the electromagnetic spectrum. The photons energise photovoltaic (PV) materials, knocking off some electrons and causing electric current to flow. The PV market has been evaluating luminescent solar concentrators (LSCs) since the 1970s, as a way to enhance the efficiency of electricity production. LSCs absorb photons that cannot energise existing PV materials and re-emit them at wavelengths that can. PanePowerSW harnessed spectrum-shifting LSCs to enhance solar cell efficiency, but also to increase the photosynthetic active radiation for plants. Using transparent materials that allow photons to pass through is counterintuitive; photon absorption is required to generate electricity. According to Nick Kanopoulos, Brite president and CEO and PanePowerSW coordinator, “the great success of PanePowerSW is its novel LSC ultraviolet (UV)-shifting nanomaterials. We divert photons in the UV range not useful for either PV panels or for growing plants and retransmit in the red and blue regions of the spectrum that are useful for both. This allows visible light to pass through the panels, while augmenting electricity production and photosynthesis, making the technology ideal for greenhouse applications.”

Higher yields, lower costs, fewer emissions

PanePowerSW optimised the LSC nanomaterials formulation and designed the transparent solar glass product to meet criteria for universal market uptake. The product was validated through deployment at a pilot greenhouse. Field testing showed a reduction in energy operating costs of up to 80 % resulting from electricity sales to the grid – a figure expected to be even higher in countries with greater solar irradiation. “The grape cultivation in our pilot greenhouse reported a negative CO2 footprint per kilogram of grapes produced: a world first for agriculture, with uninhibited scaling potential,” Kanopoulos adds. A fully automated state-of-the-art production line for inkjet printing of nanomaterials will enable Brite to deliver its solar glass at a cost significantly lower than previously possible. Kanopoulos adds: “The manufacturing technology can be easily installed with existing manufacturing line tools, making our proposition highly scalable, and all materials used for manufacturing our solar glass are environmentally friendly and fully recyclable. In short, PanePowerSW can ensure a sustainable food supply for the world, with a positive environmental impact.” PanePowerSW could soon be energising the global greenhouse farming market, helping a steady supply of sustainably produced foods reach our tables.