Solar power has a space problem. More than with other energy sources, a solar system’s output is directly related to its footprint. In densely populated European countries, however, “taking up space” is effectively synonymous with “taking away space”: from agriculture, commercial use, and nature. So before solar can contribute significantly more to Europe’s electricity mix than its current 4% (2018), space needs to be found for new solar installations.
Helpfully, solar cells are easily integrated. They can be mounted on everything from rooftops and parking ticket dispensers to the Mars rover. They can also operate on farmland – with the farmland still under cultivation. This approach, called agrivoltaics, makes solar farms compatible with, well, farms.
Agrivoltaic systems are in operation in North America, Asia, and several European countries. Demeter Agricultural Cooperative, located in Heggelbach near Lake Constance, is Germany’s first significant project. It was initiated in 2017 by the Fraunhofer Institute for Solar Energy Systems, which has a team of about twenty researchers working on agrivoltaics. Debate.Energy spoke with Andreas Steinhüser, the team’s deputy director.
Dual use sounds appealing. But don’t the solar arrays interfere with the farmers’ work?
Not at all. In agrivoltaics, agriculture is always the top priority. We make sure farmers encounter as little change as possible, except that they receive additional income. Solar technology is integrated into a farm’s existing infrastructure so that it doesn’t cause any disturbances. In some cases, it can even boost crop yields.
Can you give a specific example?
We recently launched a project involving an apple orchard. The nets that protect the apple trees from hail were replaced with solar arrays. Without significantly altering the landscape, the fruit is now protected by something that also generates green electricity.
Do the trees still get enough sunlight?
Climate change has actually resulted in apple trees sometimes getting too much sunlight. The fruit literally gets sunburn. One purpose of standard hail nets is filter out about twenty percent of the sunlight. The solar panels do exactly the same thing, except that we can control the effect better. We’re also developing dynamic panels that adapt to the prevailing weather conditions.
So dual use can actually improve the quality of the harvest?
Definitely, as Heggelbach has already shown. Most of its trees grow better under the panels than in the open air. Going forward, the aim will be to adapt the technology to individual contexts: to manufacture the panels so that a particular type of plant gets exactly the right amount of sunlight. One way we’re doing this is by building special panels that consist of both solar cells and glass that lets through sunlight.
That sounds promising. Will there soon be more of these systems in Europe?
From a technical standpoint, everything’s ready. But agrivoltaic systems need a favorable policy and regulatory environment. Germany, for example, lacks legislation to support dual use. In fact, current legislation is punitive: farmers that install solar panels in their fields immediately lose their agricultural subsidies. So agrivoltaics don’t currently make business sense for farmers. Germany is considering amendments to its Renewable Energy Law, some of which would be favorable to agrivoltaics. If they become law, that would be important progress.
What else would help agrivoltaics achieve its full potential?
Simplify the permitting process. If things don’t go smoothly, it can take up to two years to obtain the necessary permits for an agrivoltaic system for an orchard. For a commercial project, this kind of delay would be a nuisance. But it renders research projects, which have a limited duration, impossible. If I can’t start building until two years into a four-year project, I won’t see the effect on the apples. In other words, regulatory red tape hinders agrivoltaics from the very start of research and development.
Assuming that these hurdles are overcome, what is the potential of agrivoltaics in a country like Germany?
By using all the land that’s theoretically suitable Germany could install around 1,700 GW of generating capacity. That obviously won’t happen. But of all the new solar applications – on freeway noise barriers, building rooftops, and former mining sites – we believe this one has the most potential. Its maximum share of the electricity mix is likely in the single-digit percentage range. But agrivoltaics will definitely making an important contribution to the energy transition.