Construction for sun on greenhouse
20,000 solar panels will soon appear on the roofs of a horticultural greenhouse in Luttelgeest, together accounting for a capacity of as much as 8.2 MWp. Client Zonnewijzer B.V. developed the project and selected ProfiNRG because of an innovative mounting system, allowing normal solar panels to be mounted on the 4-hectare greenhouse complex.
"In 2017, I saw solar meadows springing up like mushrooms everywhere," Cor Poppe of Zonnewijzer B.V. tells of the start-up phase. "So I also started thinking about what I could do in the energy transition and that's how I gradually entered this world." Indeed, Poppe even quit his busy job and took the gamble into the world of renewable energy. Looking for a project of his own, he soon discovered that in the municipality of Luttelgeest it would not work in the form of a solar meadow. "Permits for field installations were not given by the municipality at that time," he recalls. "So I knew it had to be on a roof and started looking. That's how I stumbled upon a garden farm in Luttelgeest. Here I saw possibilities with the existing greenhouse complex and eventually bought it."
Smart solution
To develop the project further, Zonnewijzer B.V. engaged foundation Energie Expertisecentrum Flevoland (EEF). Besides providing advice, the foundation, which was set up to accelerate energy transition in Flevoland, provided funding. "A greenhouse has a construction that, at its base, is obviously not conceived from the idea of putting PV systems on it," says EEF adviser Willem Enklaar. "So you have to come up with a smart solution for that. ProfiNRG came up with a good proposal after we issued a call for tenders in the market to several parties. In the end, the company was commissioned to develop the project further with Zonnewijzer B.V."
Existing structures
This is how ProfiNRG and Zonnewijzer B.V. came together to develop an innovative system for solar on greenhouse. "The great thing about this process is that Cor Poppe had many good ideas himself," says ProfiNRG director Cees van de Werken. "His solutions dovetailed seamlessly with our proposals that are different from existing mounting systems for solar panels on greenhouses."
One such existing mounting method is to install panels over the existing glazing, effectively building two structures on top of each other. "This is far from ideal and relatively expensive, as the substructure is often not designed for the extra weight of the panels," Van de Werken said. "Another common practice is to replace the existing glass. You then mount the new frameless solar panels between the profiles of the greenhouse. The big disadvantage of this approach is that you often run into size problems. So we started looking for new ways."
Solidity
New to the project in Luttelgeest is the construction that will soon consist entirely of normal solar panels on the existing rods. Van de Werken: "This has the advantage that we are reusing as much of the existing construction as possible. We are removing the glass and applying a profile system to the rods, into which the panels can be slid. This ensures a solid construction. If you work with frameless panels, this is often very vulnerable." Not only sturdiness plays a role, the construction costs of this new construction system are also very favourable. Van der Werken: "Roughly speaking, you can say that the pricing is comparable to the cost of normal ground-mounted PV systems of similar size. We therefore expect this project to attract the interest of new parties."
Second life
Almost all lights are green for installation, and for Cor Poppe of Zonnewijzer bv, construction in Luttelgeest cannot start soon enough. "The greenhouse is now getting a second life and would otherwise have been razed to the ground. That's a good thing, so that sustainable energy can be generated for at least 25 years," Poppe said.
When completed, the project will be good for powering 2,200 households. The greenhouse's forcing function will also be partially maintained. Poppe: "When the installation is running in 2021, we will discover exactly what climate is created inside and which crops can thrive there. Nobody knows that yet, because we are dealing with a unique situation: a different type of soil, different construction, different light and a different temperature. But that's part of pioneering and it also has its charm."
