New life for greenhouse of sundial B.V.

From an interest in investing in renewable energy, Cor Poppe, owner of Zonnewijzer B.V., had the inventive idea of using a greenhouse as a support for some 20,000 solar panels. This can generate power for about 1,900 households. An interesting project, also according to ProfiNRG and Energie Expertisecentrum Flevoland (EEF). Together these parties joined forces, and after coordination with the municipality of Northeast Polder and pleasant cooperation with the province of Flevoland, the project was completed last month: the first solar panel greenhouse is a fact.

An inventive investor

Whether it would be in solar panels or wind turbines, Cor Poppe was eager to invest in green energy at a young age. "Green energy is important and it's permanent, that's what I love about this investment," Cor Poppe says. "I myself am originally from Creil and I had made remote investments before, but I never liked it. That's why I wanted to make a sustainable investment in the neighbourhood. At that time there was no policy for this from the municipality, so I had to come up with a plan myself first. A greenhouse has a large roof and after some research I found out that in theory it is possible to install solar panels on such a roof. A favourable aspect of this is that a roof is permit-free. Of course I checked this with the municipality, but they confirmed what I already thought myself: it is allowed."

EEF and ProfiNRG join forces

So in theory, a solar panel roof could be realised, but since this has almost never been done before, a party that could do it in practice had yet to be found. To this end, Cor Poppe contacted EEF. "We then selected a number of suitable parties, drafted the EPC request and had a site inspection done," says Willem Enklaar, director at EEF. "Since a greenhouse is basically not built to have PV systems on it, a clever solution had to be devised. ProfiNRG best matched all requirements. Together with Cor, ProfiNRG devised a structure that would eventually allow the solar panels to be installed on the roof of the greenhouse.


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," said Cees van de Werken, director of ProfiNRG. "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.

The solution we developed and applied together with Cor for the greenhouse of Zonnewijzer BV is a construction consisting entirely of normal solar panels on the existing rods. Van de Werken: "This has the advantage that we were able to reuse as much of the existing structure as possible. We remove the glass, and apply a profile system to the rods, into which the panels can be slid. This makes for a solid construction. If you work with frameless panels, this 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."

Next, a financing plan had to be arranged for this construction. Here, too, EEF was able to help. Inquiries were made by EEF to several funders. Then they helped negotiate and finally one funder was selected.

Dual function solar greenhouse

In the most ideal situation, in addition to generating electricity, the greenhouse can be used again in its entirety as a greenhouse where crops can be grown. Should this prove only partially possible, there are plenty of opportunities left to use remaining greenhouse space in multiple useful ways. Cor Poppe: "In solar panel country, there is a very strong search for a situation where a double function can be created. A field setup with solar panels on farmland can't do anything else. In addition, such a field setup is generally viewed by society as ugly. By placing the solar panels on the roof of a greenhouse, we hide them from the view of passersby. The visibility of the panels on the greenhouse is zero while the cost for such a structure compared to a field setup is almost the same. In the coming period, we will explore growing crops in the greenhouse during the hot summer months. There is also the option of using part of the cash as storage, should the cash function (partially) not be possible after all.

In the end, everything is profit. The greenhouse was ready to be torn down. The construction of the greenhouse was still spotless, but otherwise it was economically depreciated. The demolition had also created a lot of demolition debris. Now we can generate solar energy for the next 15 to 30 years and give the greenhouse a double function. In addition, once the economic life of the panels is over, the greenhouse can possibly be rebuilt back to a "normal" greenhouse. This is actually the ultimate form of sustainability and I think we should be heartily proud of it. I am very happy that the congregation has agreed to this and I hope we can be an inspiration to others with this. Everyone is looking for a certain duality with sustainability projects. With this, we have found one."

If Cor had wanted, he could have resold his project to various interested parties at home and abroad. Still, he chose to keep it close to home. "We have been approached several times to resell this project to (foreign) investors. We wanted to do this precisely in the polder and that's where we want to keep it. At Zonnewijzer B.V. we think along the lines of: for the polder, by the polder."

About Energy Expertise Center Flevoland (EEF).

With the Energy Expertise Center Flevoland (EEF), we help entrepreneurs, non-profit organisations and energy cooperatives in Flevoland develop, finance and realise their sustainable energy and energy saving projects. Our goal? Accelerating energy transition in Flevoland and thereby strengthening the local economy.

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About ProfiNRG

ProfiNRG is a builder and O&M party for large-scale solar installations of 250kWp and up, and supplier of total packages to installers of 100kwp and up. For more than 10 years, ProfiNRG has been providing sophisticated solar energy installations to their customers. They work directly on behalf of agricultural and wholesale businesses, governments, construction and installation companies, or on behalf of developers.