Harvesting the Sun Twice: How Researchers in Freiburg Are Advancing Agrivoltaics
Freiburg, 04/03/2026
With agrivoltaics, farmland is used twice: for farming and for energy production. In the following interview, two Freiburg researchers talk about the great versatility of the technology and the subfield of agrivoltaics research in which Freiburg is seen as a global leader.
Max Trommersdorf and Tim Krieger from the interdisciplinary ‘Agrivoltaics’ project group. Photo: FRIAS/Emily Schlegel
In the interdisciplinary ‘Agrivoltaics’ Project Group at the Freiburg Institute for Advanced Studies (FRIAS), researchers from the University of Freiburg and the Fraunhofer Institute for Solar Energy Systems are investigating the potential of agrivoltaics for the energy transition. In the following interview, the project group spokesperson Prof. Dr. Tim Krieger and Dr. Max Trommsdorff from Fraunhofer ISE explain how agrivoltaics works in practice, what the current state of research is, and what the FRIAS Project Group plans to achieve.
Herr Trommsdorff, how would you define agrivoltaics?
Max Trommsdorff: The idea is that agrivoltaics (AV) combines agricultural production and photovoltaic electricity generation on the same piece of land. Fields, orchards, or pastures are fitted with solar modules in such a way that farming can continue underneath or between them. The exact layout depends on the crop: For orchards or vineyards, for example, roof-like structures are used to allow tractors to drive through the rows. Above pastures, modules can be arranged in a way that sheep or cattle are able to graze beneath them. There’s even a configuration called ‘aquavoltaics’: In shrimp farms in Vietnam, for example, where I have conducted research, the modules span water basins, supply power for pumps, and simultaneously cool the water.
Where do we stand today with AV – in research and in practice?
Max Trommsdorff: From a research point of view, the sector has exploded over the past few years. Demonstration sites are emerging worldwide, dedicated conferences have taken place, and the number of international publications has risen from virtually zero a decade ago to more than 150 per year. Germany currently hosts only a few hundred megawatts of AV capacity, compared to roughly 100 gigawatts of total PV capacity – that’s a share of less than 1% for AV. Nevertheless, promising pilot projects do exist – for example a site installed by a winemaker on Tuniberg near Freiburg that was realized without a big project developer. On the other hand, there are schemes where the agricultural component is merely a fig leaf. As scientists we must stay vigilant and provide robust, transparent methods for evaluating the quality of AV projects.
Tim Krieger: For AV to become mainstream, suitable political and economic frameworks are essential. This includes clear rules on fiscal treatment and planning certainty for both agronomists and investors. Subsidies should be structured so that economically sound projects are attractive without creating a subsidy bubble. In my opinion, this also offers an opportunity for the domestic economy. Standard silicon solar modules are now produced far more inexpensively in China, whereas Germany focuses on specialized technologies – such as organic solar modules that can be fabricated as thin films and can filter specific parts of the light spectrum. Such technologies create completely new applications, like simultaneously optimizing electricity output and plant growth. Freiburg is one of the world’s leading research hubs for this kind of technology.
The agrivoltaic system at the Hofgemeinschaft Heggelbach. Photo: Fraunhofer ISE
What role does the new FRIAS Agrivoltaics Project Group play?
Tim Krieger: Max and I quickly agreed that we needed to combine the strengths of the University and Fraunhofer ISE. Fraunhofer ISE excels at application-oriented research, prototype development, and highly accurate measurements. On experimental plots, for example, we test different module spacings or tilt angles and systematically compare the resulting electricity and crop yields.
‘Freiburg is one of the world’s leading research hubs for this kind of technology.’
Prof. Dr Tim Krieger
Spokesperson of the ‘Agrivoltaics’ Project Group at the Freiburg Institute for Advanced Studies (FRIAS)
The University provides expertise in answering the ‘why’ questions. While previous work at the University of Freiburg has focused on building up soil organic matter and economic aspects, the collaboration with biological institutes will allow us to address questions regarding plant growth. Why does a plant behave differently under a particular module? What is the role of light spectrum, temperature, or soil moisture? And why do radishes grown under AV sometimes become elongated rather than round, complicating their marketing?
The project group brings together experts from biology, computer science, forest science, economics, and hopefully soon law and behavioural science, in order to find answers and pose new questions.
What have you found particularly interesting in your interdisciplinary work in the FRIAS project group so far?
Max Trommsdorff: What impressed me most was the reaction of the biologists to the topic. When they heard about organic solar cells – thin, flexible films that might eventually be tuned to transmit only specific light spectra – a flood of research questions manifested immediately: How does an altered light spectrum affect photosynthesis, flowering, or pest infestation? So far, solar cells have been optimized mainly for maximum power output. In AV systems, we could design them to create the optimal light conditions for particular crops. That opens an entirely new playground for collaboration between physics and biology.
‘So far, solar cells have been optimized mainly for maximum power output. In AV systems, we could design them to create the optimal light conditions for particular crops. That opens an entirely new playground for collaboration between physics and biology.’
Dr Max Trommsdorff
Fraunhofer ISE
Tim Krieger: The transdisciplinary impulse was equally exciting. Arnim Wiek, who currently holds the Humboldt Professorship for Sustainable Food Economics at the University of Freiburg’s Faculty of Economics, suggested ways to get regional companies and the public involved early on. From other areas of the energy transition, we know there is a critical tipping point: if people feel that something is being forced on them, trust quickly erodes and is hard to regain. We observed that the topic touches on so many facets that it naturally connects to various other disciplines that are still under-represented, such as law or behavioural science. The FRIAS project group gives us an excellent platform to build new alliances.
About FRIAS project groups
With the ‘FRIAS Project Groups’ funding programme, the Freiburg Institute for Advanced Studies fosters interdisciplinary collaboration at the University of Freiburg. The format brings together researchers from different disciplines to address pioneering research ideas at a very early stage of development. The programme provides scope for experimental approaches and new perspectives beyond established research structures. The funding period for the FRIAS Agrivoltaics Project Group runs from October 2025 to December 2026.
About Tim Krieger
Prof. Dr. Tim Krieger holds the Wilfried Guth Chair in Constitutional Political Economy and Competition Policy at the University of Freiburg. He is spokesperson for the FRIAS Agrivoltaics Project Group and is serving as a FRIAS Rector’s Fellow from October 2025 to February 2026. His research is located at the intersection between economics and political science, focusing on conflict and migration studies, development, and institutional change. Since 2020 he has been leading an economics-based subproject within the BMFTR-funded collaborative project ‘Agrivoltaics for Mali and Gambia: Sustainable Electricity Production by Integrated Food, Energy, and Water Systems’.
About Max Trommsdorff
Dr. Max Trommsdorff led the AV research activities at the Fraunhofer Institute for Solar Energy Systems ISE until August 2025 and is currently on sabbatical. He studied economics at the University of Freiburg and received his doctoral degree under Tim Krieger in 2023 with a techno-economic assessment of AV systems. As a member of the FRIAS Agrivoltaics Project Group, his aim is to engage engineering, agricultural, and other natural and social sciences in the field. He is a prominent figure in international AV research, co-initiator of the first global conference on the subject, and scientific chair of AgriVoltaic 2025.