Energy and food production reinforce each other at Symbizon

There are strips of land between the rows of solar panels in the solar park where various crops are grown for organic farming. The first broad beans and beetroot have already been harvested. To ensure sufficient energy yield, there are double-sided solar panels that can rotate with the sun. The reflected light from the ground, the crops and adjacent rows are captured and used for the production of solar energy. The panels can be positioned almost vertically, leaving sufficient space for agricultural machinery. Herb strips will be planted under the panels next season. Not only are they beautiful, they are also useful: they attract insects that help with natural pest control and pollination.

Continuous learning process

Vattenfall is involved in Symbizon alongside various other parties, such as ERF/Hemus and Aeres University of Applied Sciences. Eric Tonnaer, Agrivoltaics Design Lead at Vattenfall, immersed himself in agrivoltaics as an intern six years ago and is pleased that the first conclusions can now be drawn. “We’re still learning, but we’re gradually gaining a better understanding of how to get the best results from this combination of solar panels and straw cultivation.” For example, the design that allows the solar panels to rotate with the sun is hardly used anywhere else in the Netherlands. “Although we haven’t yet completed a full year of operation, I can see that the energy yield looks positive so far.”

Cooperation between all parties went smoothly. “The trick was to figure out how best to take each other’s interests into account, because they don’t always coincide.” One key thing to remember is that the solar panels need to be in a vertical position for farming. This requires good coordination and flexibility from both parties. “Tilting the solar panels still takes a lot of time, but we’re working on speeding up this process,” says Tonnaer. “We’re currently implementing these types of improvements at Tützpatz, our agrivoltaic park in Germany. We are looking to install a dashboard at the entrance that farmers can operate themselves, so that they are not dependent on us.” 

A good first harvest

Rosemarie Slobbe is managing director at HEMUS, which was founded by the ERF Foundation to facilitate innovations and developments in cultivation systems. “The first harvest of broad beans and beetroot went well. However, because we work between panels that are partly 9 metres and partly 15 metres apart, and because we grow crops on 6-metre strips, it does take some creativity to work between the panels with the right agricultural machinery.” Aeres University of Applied Sciences conducts research into the quantity and quality of crops. At first glance, there appear to be some differences between the strips. “The yield appears to be somewhat lower in the narrower test areas, possibly because there is relatively more shade there from the solar panels and it’s more humid. However, you can only really draw conclusions after you’ve monitored the crops for a number of years.” 

The site on which the solar park is located is divided into four test areas: 1) solar panels at a distance of 9 metres with strip cropping and herb strip, 2) solar panels at a distance of 15 metres with strip cropping and herb strip, 3) no solar panels, but strip cropping and herb strip, and 4) full strip cropping. In this way, we learn more about the influence of the shadow cast by the panels on the crops and herbs, for example,” says Slobbe. The amount of weeds growing between the crops was striking. This was probably caused by a combination of the excavation work during the construction of Symbizon and this year’s favourable weather conditions for weeds. 

Follow-up research

The project’s ultimate goal is to get a good crop yield for the farmer and a good energy yield from the solar panels. Tonnaer: “For example, we still need to investigate the impact of rotating the panels. What effect does this have on the growth of the vegetables? One example would be the timing of when the panels rotate: should this be when electricity prices are low or high? And does that tie in with working on the land? All of this has an effect on the end result. All processes must ultimately fit together perfectly.”

Tonnaer is hearing positive feedback from other farmers and various provinces. “We are already in talks with several parties about an Agri-PV park, but the grid connection remains a difficult issue. That is why we are currently looking at locations in the Netherlands where Vattenfall already has wind turbines, because the grid connection is already in place there.”

All participating parties are enthusiastic and eagerly await the research results. Slobbe: “We’ll incorporate these results into a new research project, Sunbiose 2, in which we’ll monitor and investigate crop yields, biodiversity and practical measures relating to irrigation. Next year, we’ll also grow other crops, which is better for the quality of the soil.”

This year’s crop yield will soon be available to taste in the restaurant at Vattenfall’s head office in Amsterdam. Part of the harvest will be used to make bean toast with beetroot spread. “This will give our colleagues in the office a tangible result of what we are doing at Symbizon in practice: a great combination of solar energy and vegetable harvesting,” concludes Tonnaer.