INNOVATION AND R&D

INNOVATION
AND R&D

GREEN & TECH MEANS BELIEVING IN CREATIVITY, INSPIRATION AND HUMAN GENIUS TO FIND NEW SOLUTIONS AND BUILD A SUSTAINABLE FUTURE.

glass is no longer the default option

Higher light transmission and reduced heat demand with a double-leaf greenhouse

For many producers, glass has always been the default choice. However, with current gasoline prices, growers are looking for alternatives to reduce heat loss in the greenhouse. “Energy saving starts at this point,” says Jelle Boeters from Filclair Nederland BV. Research carried out on behalf of the company shows that using aluminum foil can reduce energy demand by up to 28%. "Aluminum foil is considered to have lower light transmission than glass. However, the structure of an aluminum greenhouse is much thinner, so more light reaches the canopy."

"Greenhouses are incredible collectors of sunlight, but as soon as there is no radiation, the accumulated heat escapes very quickly. We have seen aluminum greenhouses that are better insulated, thus limiting heat loss , but we wanted to know exactly how much it would be and at what point it would be interesting for producers." Thus, the Hortinergy software was used to compare a glass greenhouse with an aluminum greenhouse. This computer program simulates the indoor climate and energy consumption of a greenhouse project. The thermal coefficients of the materials, conforming to the international greenhouse standard, were used. Four types of greenhouses were compared: single glazing without screen, single glazing with a screen, double inflated folio without screen and double inflated folio with a screen. With all this information, the thermal energy needs of the greenhouses were calculated over a complete tomato cycle, from December 1 to October 31.

The final figures speak for themselves. The Hortinergy simulation shows how the single-glass greenhouse without a screen would use 381 kWh/m2 per year to heat the greenhouse to 20 degrees Celsius during the day and 16 degrees Celsius at night. With a screen, this figure would drop to 290 kWh/m2. A double-inflated folio greenhouse would only require 252 kWh/m2 to achieve the same temperature levels throughout the year. Adding a screen would result in an energy requirement of 207 kWh/m2.

Thermal energy requirements for several configurations in Nantes for heating at 20°C day/16°C night (kWh/m²/month)

Light transmission “Glass is also the standard choice for producers, because the light transmission of glass is higher than that of aluminum,” continues Jelle. “It's true: if you compare two greenhouses with the same shape and structure, the double plastic cover would let in less light. However, because aluminum foil weighs less than glass, the entire structure is much thinner with the same loads. Comparing a Venlo 2x4 greenhouse with the Filclair AERO+ shape, which has a much lower peak than the competition in the Hortinergy software, there is 17% more light measured on the crop in the AERO+ infrastructure. “A thinner greenhouse structure means less shade compared to the taller structures of glass greenhouses.”

Daily mol reaching the canopy for several configurations in Nantes (mol/m²/day)

Replace the film The greenhouse film must be replaced every three years. “This is also why some growers prefer glass greenhouses: they don’t want to have to change the film. Others prefer it because they always keep an eye on the latest film technology on the market. Using double film and a special patented structure, our greenhouse is more airtight and insect-proof than our competitors. With double-layer installation, growers can also choose many configurations depending on their needs for a diffused and clear layer.Or they can opt for a cooling sheet to disperse the light so that the temperature drops during the summer.Also, coatings can be applied to the aluminum greenhouses.

Additional broadcast In recent months, the company has seen growers in regions traditionally filled with glass greenhouses seek out aluminum options. “Norway, for example,” says Jelle. “In the past, aluminum greenhouses were considered only suitable for southern regions, but today's aluminum structures are more similar to glass structures.” In addition, the initial investment in our structure is more advantageous. “But that’s not where you’ll find the biggest benefits,” Jelle concludes. “It’s really 25% lower heating demand.” With gas prices of the past, these numbers were also relevant, but with gas prices today, it can mean the difference between losing money, breaking even, or making a profit. profit. At the end of the day, it’s the return on investment that matters.”

Nicolas julien, R&D engineer at filclair

“Vertical solar panels under the gutter provide significant savings in plastic greenhouses”

After being asked to delve into photovoltaic plastic greenhouses, Nicolas Julien, R&D engineer at Filclair, quickly concluded that placing solar panels on top of a plastic greenhouse would not work because the systems would be too heavy for the structure. However, there are opportunities to turn sunlight into electricity in a plastic greenhouse, according to recent research: by placing solar panels inside the greenhouse, under the gutter. Vertically, that is. A simulation shows that it could reduce the net heating costs of a greenhouse to around 50,000 euros per year per hectare.

To put these results into perspective and focus on a specific case, Nicolas referred to the Agrithermic study using Hortinergy software, which demonstrated that a Filclair double inflated ETFE greenhouse could benefit from +18% more light. than a Venlo glass greenhouse. If nine rows of vertical bifacial panels were installed under this ETFE greenhouse at a height of 1.3 meters, the drop in light due to the panels would exactly compensate for this +18% surplus of light under the ETFE greenhouse, thus maintaining the yield agricultural with additional energy production. "For a one hectare tomato greenhouse, with double inflatable ETFE cover and thermal screen, assuming an energy cost of 40 euros/MWh for gas, the heating costs would be around 80,000 euros per year in heating the greenhouse to 20°C during the day and 16°C at night all year round except in November. The photovoltaic system would reduce the net heating costs of such a greenhouse to around 50,000 euros per year per hectare."

Of course, to arrive at a reliable projection of electricity production for this specific configuration, one would need to conduct field experiments to address technical uncertainties, such as heating the panels inside the greenhouse. “A more in-depth techno-economic analysis based on real-world conditions would therefore be essential to build a viable economic model for these relatively new agrivoltaic greenhouses. Nevertheless, the use of bifacial solar panels in greenhouses has the potential to bring multiple benefits . such as increasing energy production, improving crop yield and reducing environmental impact."