When the combine harvester makes its way under solar power modules

When the combine harvester makes its way under solar power modules

High temperatures, little precipitation: new ideas are needed to counter climate change. Agri-photovoltaics could be one such project – it combines solar power production and agriculture on one and the same flat surface. "An exciting thing for particularly dry areas," says simon gruber of the fraunhofer institute for solar energy systems ISE. "Especially for franken."

The fact that photovoltaic elements are arranged close together on a flat surface is a familiar picture. They stand on fields that are no longer used for cultivation. However, a research project in the lake constance region shows that it does not have to be an "either-or" situation, but that agriculture and solar power generation on the same flat can go hand in hand. Simon gruber, an agronomist at the fraunhofer institute for solar energy systems ISE, recently presented the project as part of the "kreisacker" environmental education program in kitzingen, germany.

"Agrophotovoltaics: contribution to resource-efficient land use (APV-RESOLA)" is the title of the research project launched in 2016 at a demeter farm on lake constance and required by the federal ministry of education and research. "It’s about dual use of flat land," explains simon gruber. In total, the arable land covered around 2.5 hectares, part of which, namely 0.34 hectares, was equipped with a solar system: solar modules with an output of 194 kilowatts were installed at a height of five meters. Among them, the farm grows winter wheat, potatoes, clover grass and celery – wheat because it occupies the largest acreage in germany. Potatoes, because the nightshade crop requires somewhat less light than wheat, for example. The trial showed that cultivation was not a problem from a technical point of view. The farmer was able to work under the modules without any problems, even with a combine harvester, says gruber.

Research also in fruit growing

That land use efficiency is higher when a flat is double-shaded is unsurprising. But how does the agricultural yield develop? Does the crop yield increase when the flat is shaded by the solar panels, or does it decrease because of a possible lack of light?? What about the quality of the harvested products?? How is the microclimate developing under and next to the research facility?? Does the soil dry out less when the sun is not shining directly on it?? These questions were followed with excitement by both the members of the cultivating association and the scientists from the fraunhofer institute and the university of hohenheim, especially since the two trial years 2017 and 2018 offered completely different framework conditions. "2017 was a relatively normal year with usual precipitation, 2018 was a dry year," simon gruber looks back.

In both years, land use efficiency was high, 160 percent for wheat in 2017 and 186 percent in 2018 when combined with potatoes. Not only was more solar power produced in the hot summer because of the stronger solar radiation, but the partial shading of the flat also led to a higher yield for three of the four cultivated crops than on a reference flat without solar modules. "This is a super exciting result", says simon gruber. He hopes that experience can continue to be gained, also with other crops, also in other areas. As of this year, another research project in rhineland-palatinate is shedding light on agri-photovoltaics in apple cultivation. "Especially in fruit growing, we see a rough potential for synergies," explains gruber. The solar modules could take over the function of the hail protection nets, which thus become superfluous. In the research project at lake constance, the energy generated in the fields was stored on site by the farming community and used by the farmers themselves, thus minimizing the energy costs for the farmers. "This is of course ideal," says gruber.

The agricultural scientist from the fraunhofer institute admits that, economically, agricultural photovoltaic systems are not yet competitive with conventional ground-mounted systems because of the higher costs for the substructure. They are more expensive than ground-mounted systems, but at the same time they are already more favorable than small photovoltaic systems on roofs. The institute is working hard to install more pilot plants to gain experience. Especially since there are various system approaches – they can also be installed vertically, for example. "These modules then stand pretty close to the ground, upright, like a fence," explains simon gruber.

First considerations at the LWG

The main challenge in agri-photovoltaics is "the regulatory framework". It’s all about demand programs and permits for these types of facilities. Gruber advises farmers who want to implement such projects not to simply start an approval process. "You should definitely get the farmers on board right from the start," explaining what’s happening and why. "The social aspect is important."

Presenting innovative projects and stimulating discussion – that was the goal of the ESD team at the district office with this and other presentations. About 30 citizens attended the event, including farmers and gardeners. "There were participants who showed interest in principle," reports verena volkamer of the ESD team, "some had already looked into similar systems / forms of land use.

Hermann willfarth from huttenheim also finds the combination of energy production and agricultural cultivation on a flat area very exciting. Already professionally, he deals a lot with the topic of energy in agriculture, is responsible for advising farmers on energy saving and energy efficiency at the agricultural office in uffenheim.

But also privately, as a winemaker in the wine paradise, he has a great interest in the subject and has even thought about setting up a pilot plant. It would be interesting to find out what effect these systems have on early varieties such as bacchus, for example, whose fruit burns easily when exposed to strong sunlight.

According to the head of the viticulture department, georg batz, the state institute for viticulture and horticulture is currently "in the very early stages of consideration" with regard to agri-photovoltaics. Such systems are interesting from an energy point of view, but if vineyards are simply covered over with them, it will have an impact on the landscape. At the moment, information was being gathered on the various system combinations and it was being considered where a model could be installed. The problems of shade and drought had to be taken into account. "At the moment we are looking and sifting, and then we will decide how to proceed."

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