Germany: Lake Constance: Solar roof over apple trees to be profitable without subsidies

In Kressbronn, solar panels installed above apple trees supply electricity directly to a sorting facility. A battery storage system is intended to make the project profitable without subsidies.

At the Bernhard Orchard in Kressbronn on Lake Constance, solar panels span the apple trees; the facility has been operational since October 23.

The project developer describes it as Europe’s largest agrivoltaic installation over an apple orchard. It delivers a peak output of 2.4 megawatts, complemented by a battery storage system with a capacity of 3.4 megawatt-hours.

More interesting than the facility’s power output is its business model: it is designed to operate economically without any subsidies.

As SONNTAG Energy announced at the inauguration, the Tettnang Machinery Ring built the installation. The orchard itself is the owner, ensuring that value creation remains on the farm.

Purely in terms of calculations, the amount of electricity generated is sufficient to supply approximately 600 households.

Electricity to the neighbor via a cable

Part of the solar power generated on the farm is transmitted via a dedicated line directly to BayWa Obst’s apple sorting facility, located approximately 500 meters away. This arrangement is based on an on-site power purchase agreement (PPA), a supply contract between the producer and the neighboring consumer that bypasses the public grid. BayWa Obst also describes this direct connection in a press release.

The operators also intend to use the storage system to respond flexibly to the electricity market.

The system has a clear purpose: to decouple power generation from sales in time. Electricity generated at midday can be stored and sold later at more favorable prices.

Modules as a protective roof

Suspended above the trees are semi-transparent modules. They allow light to reach the fruit while simultaneously providing protection against hail, heavy rain, and sunburn.

At the inauguration, fruit grower Hubert Bernhard emphasized that the modules should offer protection to the trees while allowing sufficient light to pass through. In stone fruit cultivation, hail or sun protection nets are already widely used; the modules can assume this function.

Therefore, in an interview with the Obersulm Climate Forum, winemaker Markus Gruber considers apples and other stone fruits particularly suitable for this application. In viticulture, however, he sees no possibility due to the use of machinery.

However, pilot projects in viticulture show that vines under modules can also cope better with weather extremes.

This concept is not entirely new for the farm. As early as 2022, a 0.4-hectare pilot installation with a capacity of approximately 230 kilowatt-peak was commissioned on the site.

At that time, the farm already observed, according to BayWa Obst, that less water and plant protection products were required. Whether this can be transferred to the larger installation remains to be seen.

What the research says – and what it does not

Kressbronn has not yet provided reliable data on apple yields.

A field study conducted by the University of Hohenheim and the Jülich Research Centre in 2023 and 2024 examined barley, field beans, potatoes, cabbage, and maize at five locations. Most crops coped well with partial shading, with maize being the most sensitive.

Apples were not included in the study, so the findings can only be applied to apple cultivation to a limited extent.

The Fraunhofer Institute for Solar Energy Systems (ISE) estimates a potential of 136 or 98 gigawatt-peak on sites with high synergy between solar modules and plants, depending on how strictly protected areas are excluded.

Germany’s photovoltaic deployment target for 2030 is 215 gigawatt-peak. The ISE potential analysis therefore indicates that agrivoltaics could account for a significant share of this expansion.

Barriers in the grid and regulations

Whether the calculation without subsidies actually works out cannot be verified from the outside: the parties involved remain silent on investment costs and revenues.

Mark Kugel, co-founder of SONNTAG Energy, calls for more flexible grid connections and practical rules for the direct supply of neighboring consumers. Storage systems should also be allowed to use both solar and grid electricity. Previous projects have already encountered planning and legal hurdles.

For fruit growers, Kressbronn thus serves as a blueprint with conditions: a large consumer in close proximity to the grid, storage for flexible marketing, and crops that require a protective roof must all come together.

Whether other farms will follow suit will likely also depend on whether the legislature relaxes the rules for storage and grid connections.