You might imagine that enough solar panels on the many roofs in the Netherlands would contribute to generating green energy, yet more is needed to achieve the energy transition. That's why Triodos Groenfonds has been investing in businesses promoting a climate-neutral future with innovative projects for the past 25 years.

One of these businesses is GroenLeven, a market leader and specialist in developing large-scale solar energy projects in the Netherlands. When it comes to scale, GroenLeven leads the way with two key projects, a floating solar park and solar panels integrated into the roof of a greenhouse complex.

Willem Biesheuvel, Project Manager at GroenLeven

Floating solar park
Anyone who spends time in nature or enjoys swimming knows that the Netherlands has several lakes created by industrial sand excavation. When the sand extraction has finished, these lakes can easily be 20 to 30 metres deep in the middle, and often it is only the edges that are used for recreation.

What a good place for solar panels, thought GroenLeven. The company have developed floating solar parks in Tynaarlo and near Deest, but since 2022, Europe's largest solar park has been floating in the quarry near Sellingen in the province of Groningen. "Several things converge in Sellingen," says Willem Biesheuvel, project manager of GroenLeven proudly. "Sand extraction is still taking place in the northern part of the lake, but extraction work has stopped in the southern part. People use one side of the lake for swimming, but apart from that, there is no other activity. It’s a perfect spot for a floating solar park," Biesheuvel argues.

Multi-function sites
It is this dual functionality that GroenLeven believes is important. Biesheuvel: "A small section of the water is used for recreational activities, but at least 30 hectares of the water surface is unsuitable for surfing or boating. More than 76,000 solar panels mean we can now supply at least 12,000 households with green electricity."

Does the arrival of the floating solar park harm the existing ecology in and around the lake in Sellingen? “There is often little life in the lakes created by sand extraction sites because the acidity is too high for that," Biesheuvel explains. Hanze University Groningen and Wageningen University & Research have both studied life around the lake. "The results show that the birds that live on and around the water, including the tundra goose, like to rest on and among the solar panels," says Harold Hofenk, Energy & Climate relationship manager at Triodos Bank. "And work is underway to redesign the banks along the lake with high and lower sections to create wet and dry parts. This benefits the biodiversity of the area."

Solar panels on greenhouses
This dual purpose, which allows the same location to serve multiple functions - including contributing to energy transition - can also be found at the greenhouses in Middenmeer. GroenLeven has partnered with Royalpride, a large horticultural greenhouse company, to create a unique greenhouse complex specially developed with integrated solar panels as a roof. These panels allow enough light through to grow certain crops.

"The solar panels form the roof of the greenhouses like a kind of carport," Biesheuvel explains, "with panels facing both east and west. The panels generate 31 megawatts of peak energy over 16.5 hectares. It is currently the only location in the Netherlands where this happens on this scale." The solar panels allow slightly less light through compared to a standard greenhouse roof. The project is investigating which fruit and vegetables grow best under the panels and if additional (sustainable) lighting is needed - which is not unusual in regular horticulture.

Harold Hofenk explains that the yield and consumption of energy are closely linked, making the project unique. "The energy generated can be used near the production site. This saves money, extra resources and power pylons above ground because the energy doesn't have to travel from the north of the Netherlands to the west before it is used. The energy generated by the solar farm in Middenmeer goes directly into the grid and is used locally, an initiative that Triodos Groenfonds is pleased to support."