With the new solar modules, greenhouses can generate their own energy without affecting the plants

Plants only use light waves from part of the spectrum for photosynthesis; the rest can be recovered and used to produce solar energy. This is the idea behind the solar modules developed by the EPFL company Voltiris. After good preliminary results, a new pilot plant was recently installed in Graubünden.

In Switzerland, the cultivation of tomatoes, cucumbers, peppers and other vegetables that require a lot of light and heat requires greenhousesbut its operation consumes a lot of energy.

Farmers must carefully balance crop yields and economics with concern for the environment.

Heating a 5 hectare greenhouse costs more than 1.5 million francs per year. And a greenhouse of this size emits about the same amount of CO2 per year as 2,000 people.

Nicolas Weber, CEO of Voltiris.

The Swiss Federation of Fruit and Vegetable Producers, which farms several thousand hectares throughout the country, has set itself the goal of eliminate all fossil fuels from its agricultural processes by 2040.

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Voltiris system.

The system developed by Voltiris can greatly contribute to achieving this goal. Its technology is based on the fact that plants do not use all the waves contained in sunlight; the rest can be concentrated in photovoltaic cells to generate solar energy.

The Voltiris system is lightweight and designed to follow the movement of the sun across the sky, and has a daily performance equivalent to that of conventional solar panels. The first vegetables grown with the Voltiris system were harvested this summer thanks to pilot tests in two greenhouses, in the cantons of Valais and Graubünden.

Sunlight is essential for crops because plants need it not only for photosynthesis, but also for phototropism (causing plants to grow in the direction of light) and photoperiodism (how organisms respond to changes seasonal length of day).

But plants are picky about which parts of the spectrum they use, relying on red and blue light. This is why Voltiris filters allow these wavelengths to pass and direct the others (green and near infrared) towards the photovoltaic cells, where they are converted into solar energy. In addition, the system generates this renewable energy without reducing crop yieldsbecause the plants continue to receive all the sunlight they need.

The system consists of dichroic mirrors, which show different coloration depending on the viewing conditions. The color of the glass, reminiscent of the anti-reflective coating of the glasses, gives the mirrors an almost decorative appearance because they change color depending on the light passing through them.

Two patented inventions make the Voltiris system unique and able to work so well. The first is an optimized optical system that effectively concentrates sunlight, and the second is a solar tracking device designed for use under the roof, which extends the time the system can produce power by 40%. solar.

Thanks to these advances, the system can achieve yields similar to those of conventional photovoltaic panels but with only half of the light waves, ie green light and near infrared.

We plan to apply different treatments to reflective glass depending on the needs of certain crops, to further improve yields. The installation fits into the empty space between the roof of the greenhouse and the tops of the plants.

Nicholas Weber.

Satisfies 60 to 100% of the energy needs of a greenhouse.

Pilot testing of the new system has shown that it should be able halve CO2 emissions from greenhouseswhile ensuring between 60% and 100% of your energy needs depending on the heating system installed.

Emissions will not be reduced to zero as our system will begin to replace electricity, which is often ‘cleaner’ than gas. This translates into an environmental benefit, but also a financial one, once the cost of the system has been recovered, which should take between four and seven years.

Nicholas Weber.

The Voltiris innovation comes at a good time, as the Swiss federal government has introduced incentives in recent years to encourage greenhouse operators to reduce their dependence on fossil fuels for heating. These incentives include grants for clean energy systems. But the existing alternatives, such as wood, biofuels and geothermal energy, will probably not be enough. For him, the technology developed by Voltiris promises to be an attractive solution.

The company plans to conduct further pilot tests in the Netherlands and Geneva before commercializing its product in the second half of 2023.

Going through epfl.ch

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