28.03.22 “The ideal aim would be carbon-neutral production of apples” Interview with Jürgen Zimmer • Reading time: 4 min.

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Is agrivoltaics also compatible with stone fruits? Jürgen Zimmer of the Dienstleistungszentrum Ländlicher Raum Rheinland-Pfalz (DLR) is investigating this question. The aim is to test on a range of apple varieties whether it is possible to combine cost-effective production of these with electricity generation.

Mr Zimmer, the Dienstleistungszentrum Ländlicher Raum Rheinland-Pfalz (DLR) is involved in a research project involving agrivoltaics. Could you describe this project in a little more detail?

This is the first project anywhere in Germany that is investigating agrivoltaics in fruit cultivation in relation to apples. In spring 2021, we planted eight apple varieties on an area of about one hectare. Some of the plants are grown, respectively, under film, hail nets, and transparent PV elements. Here we have a tracker system – meaning modules that follow the position of the sun – and permanently installed modules, which also differ in the arrangement of the solar cells. The PV installation has a maximum capacity of 258 kilowatts. The site is located in Grafschaft-Gelsdorf in the Ahrweiler rural district.

Who is involved in the project?

In addition to us, the participants are the Fraunhofer Institute for Solar Energy Systems, BayWa r.e., EWS Schönau and Fendt. The project receives backing from the federal state of Rhineland-Palatinate and the Federal Ministry for Economic Affairs and Climate Action. Our role is to provide support from the perspective of agricultural science. I must also not forget Johannes Nachtwey and his fruit-cultivation business, on whose premises the project actually takes place! He not only made the site available but also played a major part in driving the process of obtaining the necessary permits and completing the building application. Nothing would happen without innovative farmers like him.

What exactly are you investigating in your project?

Basically, it is about bringing apple production and agrivoltaics together. Specifically, what it means is that we will spend the next five years investigating how agrivoltaics can protect apples against hail, sunscald, frost, or extremely high temperatures. At the same time, we want to test whether and how shading from the various solar modules impacts growth and yields. The hail nets and film are used here for comparison, because one aim is to answer the question whether solar modules can take the place of hail nets and film as protection systems. An additional aim is to boost resilience in fruit cultivation and to make a contribution toward resource-efficient land use. One very important factor when the PV units were being set up was that the agricultural work here should be governed by the same conditions as those applying to “traditional” espalier fruit trees. In addition, biodiversity measures were carried out – for example, by planting flowering shrubs and native wild-herb mixes. With the battery-powered tractor supplied by Fendt, we aim to identify the potential for cutting CO2 emissions by using green energy instead of diesel-powered tractors.

So far, we have spoken only about the plants. What about the PV?

I must stress that we are investigating here whether agrivoltaics can be used to engage in fruit cultivation on a scale that is economically successful. Other projects have already shown that this can be done with soft fruit, which is partly because blueberries or raspberries, for example, can cope well with shading. We are testing whether stone fruits are also able to handle it well. But, of course, it is also about generating electricity, although we are less interested in doing this to sell the energy. On the test site, we are using both the e-tractor and battery-powered processing machinery and measuring the CO2 savings. We are also able to run the cold store for the apples with the electricity that we have generated ourselves. In other words, our ideal aim would be carbon-neutral production of apples that is economically – meaning, in terms of yield and marketability – on a par with traditional methods.

When do you expect to see the first results?

As we were able to start planting only in May 2021 – after the PV installation was completed – we were not able to harvest much in that year, and the same will be true this year. I expect to see significant yields in two years from now. We shall already be gathering data between now and then, of course, but only then will we be able to make reliable assertions about the project’s agricultural production.

From your perspective, what does the future look like for agrivoltaics?

Fundamentally, I regard the concept as a good contribution toward easing the problem of land-use competition between the production of renewables and agriculture. What is decisive for its continued expansion, alongside projects like ours, is political decision-making. The fact that Germany’s federal government and the state of Rhineland-Palatinate are supporting the project shows that the potential of agrivoltaics is recognized. On the ground – and this often varies from one rural district to another – there are differences in the level of support regarding, for example, the granting of building permits. Fortunately, we have experienced great support from the Ahrweiler district administration. I am expecting further simplifications here in the future. Overall, I’m feeling positive!


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