Héliovert’s new offer makes it possible to install photovoltaic panels on the roof on grassland-like vegetation chosen for its high evaporation rate. This synergy lowers the temperature by several degrees, especially at high temperatures, which allows to increase the production efficiency of the modules.
Ecovégétal, a company specializing in green roofs and permeable parking garages, launched a new offer in 2021 called Héliovert, which combines roof greening with the installation of solar panels. “The idea of exploiting the synergy between these two technologies arose from a study currently being conducted by Cerema in Nancy,” confides Pierre Georgel, CEO and founder of Ecovégétal. pv magazine France†
This expert laboratory in the field of environmental, infrastructure, climate and energy issues has been working on the PROOF project since 2019, which aims to assess the energy contribution of a green roof to the electrical efficiency of a solar panel. “The first results show an increase in the electricity production efficiency of 8 to 10% thanks to the presence of vegetation that acts as a thermal regulator under the photovoltaic panels,” continues Pierre Georgel.
Hence the solution developed by Ecovégétal that combines the installation of a green roof and photovoltaic panels. “But it goes much further than just laying grass on a roof, Pierre Georgel notes. It is indeed the vegetation that serves as ballast for the mounting system of the solar panels”.
In detail, a drain of type XD20, DK20 or equivalent is laid over the entire surface of the roof and serves as an anti-root sealing system and for rainwater retention at a rate of 7 litres/m². A plate made of recycled plastic is installed on top. “This plate will serve both as a water drainage basin and as a mounting bracket for the aluminum frames at an angle of 15° on which the photovoltaic panels are installed, explains Pierre Georgel. It is therefore not necessary to drill into the roof construction”.
Finally, a Saxalis 1.1 substrate, based on mineral additives enriched with organic matter, is spread over the roof. It benefits from an A2FL-S1 fire rating. Finally, a flowering meadow-like vegetation is planted that can change color with the seasons. The plants were chosen because of their high evaporation rate, which reduces the temperature on the roof by a few degrees, especially in hot weather.
“We are already using this green solution for the thermal insulation and heat island compensation properties in the city,” recalls Pierre Georgel. On a roof terrace, the presence of certain plants is even a bulwark against fire risk. Finally, we are witnessing the return of biodiversity to the urban environment: local fauna (birds, pollinating insects, etc.) and the reintroduction of flora adapted and resistant to its environment”.
In addition, the choice of photovoltaic modules is determined by the partner electricians with whom Ecovégétal works, according to the wishes of the customer. These can be south, east/west, ridge, butterfly, depending on the geographical area and biodiversity… Predetermine the thickness and dry weight of the substrate – ie the weight of the soil and vegetation in severe drought – is the subject of a study to ensure the resistance of the solar panels to the wind.
One of its first clients is the company from Broue (28) that is currently carrying out the roof project for the industrial Bosch headquarters in Saint-Ouen (93), coordinated by the firm MAA Metropolis Architectes Associés. An area of 990 m² will be planted and 790 m² will be covered with 395 photovoltaic modules.
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