Construction for sun on greenhouse
20,000 solar panels will soon appear on the roofs of a horticultural greenhouse in Luttelgeest, 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, which allows normal solar panels to be mounted on the 4-hectare greenhouse complex.
"In 2017, I saw solar farms springing up like mushrooms everywhere," Cor Poppe of Zonnewijzer B.V. says of the start-up phase. "So I also started thinking about what I could do in the energy transition, and that's how I got into this world from there." Indeed, Poppe even quit his busy job and took the gamble into the world of renewable energy. Searching 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 setups were not given by the municipality in those days," he recalls. "So I knew it had to be on a roof and I started looking. That's how I stumbled upon a market garden in Luttelgeest. Here I saw possibilities with the existing greenhouse complex and eventually purchased it."
Smart solution
To develop the project further, Zonnewijzer B.V. engaged foundation Energie Expertisecentrum Flevoland (EEF). In addition to consulting, the foundation, created to accelerate Flevoland's energy transition, provided funding. "A greenhouse has a construction that, of course, in the base, is not conceived from the idea of putting PV systems on it," says EEF consultant Willem Enklaar. "So you have to come up with a smart solution for that. ProfiNRG came up with a good proposal after we made a call in the market to several parties. In the end, the company was commissioned to develop the project further with Zonnewijzer B.V."
Existing structures
So 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 himself had a lot of good ideas," says ProfiNRG director Cees van de Werken. "His solutions fit seamlessly with our proposals that are different from existing mounting systems for solar panels on greenhouses."
One such existing installation method is to place 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 to handle the extra weight of the panels," Van de Werken said. "Another common practice is to replace the existing glass. Then you 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."
Firmness
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 remove the glass, and apply a profile system to the rods, into which the panels can be slid. This ensures a solid construction. If you work with frameless panels, it is often very vulnerable." Not only sturdiness comes into play, but construction costs of this new structural 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 begin soon enough. "The greenhouse is now getting a second life and otherwise would have gone to the ground. That's a good thing, so it can start generating renewable energy 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 up and running in 2021, we will discover exactly what climate is created inside and what 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."
