Dr. Andreas Schweiger is head of the Department of Plant Ecology at the University of Hohenheim. As part of the research project “Synergetic integration of photovoltaics in agriculture as a contribution to a successful energy transition” (SynAgri-PV), he is investigating the influence of agrivoltaics on the yields and yield qualities of crops. The test site is the Hofgemeinschaft Heggelbach, a Demeter farm on Lake Constance, which operates a high-mounted agrivoltaic system with an area of 0.3 hectares. In the interview, Schweiger reports on the status of the research. Together with Florian Reyer from the farm community, he will report on his experiences at the Öko-Feldtage.
Since 2017, you have been investigating the effects of the photovoltaic system in Heggelbach on yields of different crops such as winter wheat, potatoes and celery. What does your data say so far?
Andreas Schweiger: With sufficient rainfall, the yields of the crops under the system were lower. Wheat in particular reacted more sensitively here than potatoes or celery. In years with persistent drought, however, the plants under the system were more productive than in the open fields. Here too, celery and potatoes benefited more than winter wheat. It therefore appears that the photovoltaic system promotes the resilience of the crops to extremes.
What factors are decisive for these differences?
Schweiger: The opaque modules affect the availability of light on the surface. This impairs the plants’ photosynthesis and has a negative effect on productivity, especially when there is enough water available. However, as the shading also leads to less evaporation and plants are therefore less stressed by drought, this in turn has a positive effect on productivity during dry periods.
Based on the current state of knowledge, do you think it makes sense to integrate photovoltaics into agricultural land?
Schweiger: Yes, if only because agriphotovoltaics can contribute to independence from fossil fuels. It can also make agriculture more resilient by mitigating the effects of extreme years and generating energy at the same time. Of course, photovoltaics makes farming more challenging, but practitioners are increasingly gaining experience in this area.
Which crops are particularly suitable for cultivation under the plants?
Schweiger: In principle, crops that are sensitive to drought and at the same time shade-tolerant are particularly suitable. Pome fruit or soft fruit are good examples, but of course you don’t cover as much area as you would need for a large-scale expansion of renewable energy production. It is also very dependent on the location and climatic conditions. The more extreme weather conditions that are expected in the future will make the plants interesting for various crops. In extreme cases, even maize can benefit from the effects of the system.
The Eco-Field Days 2023 will address the topic of agrivoltaics in a large special area. The Ministry of Food, Rural Areas and Consumer Protection Baden-Württemberg (MLR), together with the Fraunhofer Institute for Solar Energy Systems (ISE), the University of Hohenheim and other state institutes, will present experiences from projects in Baden-Württemberg on 200 square meters. Visitors can find out about the research work and results to date. A model plant from the MLR will also be used to illustrate the crop cultivation, business management and building law aspects of agriphotovoltaics. Various companies will be presenting their agri-photovoltaic systems on a further 400 square meters. Visitors will also be able to find out about technology already available on the market.
Dr. Andreas Schweiger is Junior Professor and has been Head of the Department of Plant Ecology at the University of Hohenheim since 2020. He studied Environmental Engineering (Dipl. Ing.) and Biodiversity and Ecology (M. Sc.) and completed his doctorate at the Chair of Biogeography at the University of Bayreuth. His research focuses on the investigation of plant reactions to environmental changes. Photo: University of Hohenheim.
Producing food and electricity in one area can save resources. Photo: Fraunhofer ISE