28.03.22 “A year to get planning consent” Interview with Fabian Karthaus • Reading time: 4 min.

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A much bigger crop of fruit and better protection for the plants: farmer Fabian Karthaus grows berries near the German town of Paderborn and, at the same time, harvests solar electricity. He is pleased with his yields, but it is the red tape that is driving him to despair.

Fabian Karthaus, can you briefly describe your agrivoltaic system to us?

Together with my partner Josef Kneer, I grow pick-your-own blueberries and raspberries on an area of half a hectare. There are also apple trees there. The plants grow under a roof of translucent solar modules that is three meters high. The frames are made of aluminum and the panels can be fitted and replaced from underneath. Rainwater is collected and used to water the plants via an irrigation system. The whole thing is really a “greenhouse,” because the roof covers the whole area and there is the option of enclosing the sides with sheeting, for example if the weather in winter is very cold.

How did you get the idea for the project?

I have been operating a solar farm with a business partner for some time, so I was familiar with photovoltaics. I was also breeding pigs and, in 2018, I decided that I needed to diversify, so I began growing berries. The soil here in the Paderborn region is very stony and dry. Climate change is making it even drier and exposing the plants to even more sunshine. That is why I opted for a greenhouse solution, where it is easier to control the temperature, the sunlight, and the watering. After looking at some existing farms, for example in the Münsterland area, I suddenly thought: why not have a roof made of glass PV modules and combine agricultural production with electricity generation? After a long search, I finally found the ideal technology company in Bavaria and they set up the technical side of things at the start of 2020. The first harvest was in the spring of the same year.

What has your experience with your agrivoltaic system been like?

We have around 2,700 solar modules that generate a peak power output of 740 kilowatts and, from a financial perspective, we’re happy with that. We also have a respectable yield of berries. The plants grow better, bear far more fruit, and are protected against too much sunlight, hail, and drought. They also fruit later in the year, which enables me to extend the period when our customers can pick and buy the berries. Alongside the greenhouse, there is also an open area where I am growing the same varieties so that I can compare the yields. These plants fruit around two weeks earlier because they get more direct sunlight. When they are over, the season in the greenhouse starts. In financial terms, I am very pleased and I am planning a much bigger system covering 4.5 hectares with a peak power output of 7.5 megawatts for next year. Another factor that is important to me is that my system and others like it help to protect insects. We also keep bees and they love the flowers on our berry bushes and fruit trees. The more systems like this the better.

How long did it take to build?

Our partner company completed the construction in just a few weeks under fairly adverse conditions. All credit to them! But that was not the real challenge.

Which was?

The fight with the authorities! For a system of this size you need all kinds of approvals and expert reports covering fire prevention, protection of birds, structural calculations, and many other things. And then you need to sort out the connection to the grid. Our greenhouse requires special approval and that currently applies to all agrivoltaic systems, because planning law does not allow land to be used simultaneously to grow plants and produce solar energy. It took us a year to get planning consent. Then when the approval date had been set, we were accused of simply wanting to get our hands on the feed-in tariff. The chamber of agriculture was also unwilling to approve the system at first. Finally, this all ended in a legal dispute, which we won.

Now the German government has announced that it intends to subsidize agrivoltaics in the future…

That is a good thing and also very important. But the decisive factor is what the planning authorities at a local level do, because they have to approve the projects. It may be that the authorities in one district block the expansion of agrivoltaic systems, while in the neighboring district planning law is interpreted in favor of agrivoltaics. This has to change if agrivoltaic systems are to be successful. In the meantime, the authorities seem to be taking a new approach and even our local chamber of agriculture is now interested in our experience of agrivoltaics! Plus last year we won the German solar prize.

Finally, let’s take a look into the future. What do you think are the opportunities for agrivoltaics in Germany?

Of course, it is not possible to operate systems like this everywhere. It makes no financial sense to fill the huge arable fields that are used to grow maize or wheat, for example, with steel frames for solar modules. The machines have to be able to operate and they are both very tall and very wide. But for specialized crops such as berries, other fruit, and perhaps also vines, agrivoltaics represents a huge opportunity. It improves yields, supports the energy transition, and helps to protect the environment and the insect population.


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