Home – Energy – A Bavarian farmer mounted solar panels 23 feet above the poles holding up his hops, and the harvest made more electricity but fewer cones
Could the beer you enjoy during a football game at the pub play a part in generating renewable energy? Bavarian hop farmer Josef Wimmer set out to see if his crop could do exactly that. While contemplating the 23-ft. trellis system across his field, he got the idea to install solar panels on top, and completed the project in 2023.
It generated electricity for about 200 homes, but the shadow cast on the plants limited the growth of hop cones, the thing that brewers actually buy.
That setback did not end the experiment. A second prototype installed in 2025 tilted the modules from 20° to 45°, giving the plants more light, spreading generation into the morning and late afternoon, and catching more low winter sun. The lesson is simple but useful, since agrivoltaics works only when the panel geometry suits the crop, not just the grid.
The official HoPVen research site covers over 3 acres and combines Hallertauer Tradition and Herkules hops with a 977-kilowatt solar array. Its modules sit 23 ft. above the ground on sturdy steel masts that also serve as hop poles, allowing farming to continue below the glass.
On the first version, the panels were set at 20°, close enough to horizontal to collect strong midday sun. The same layout cast too much shade at the top of the trellis. When the vines reached the roof, they pushed out bushy growth instead of enough cones, reducing both the harvest and the extract that brewers value.
Engineer Bernhard Gruber spent two years reworking the design. The 2025 prototype uses steeper panels that reduce the strong noon shadow and let the hops devote more energy to cone production. It also spreads electricity generation across more valuable hours, rather than concentrating output around midday when Germany’s grid may already be flooded with cheap solar power.
The economics is still a balancing act. Researchers measured hop losses of 10% to 20%, while Wimmer said the farm can still make the numbers work if losses settle between 10% and 15% because electricity revenue fills the gap. “It pays off, it pays off,” he said, while Gruber estimated a roughly 14-year payback for equipment expected to last at least 30 years.
HoPVen runs from November 2023 through October 2026, with Fraunhofer ISE, Weihenstephan-Triesdorf University of Applied Sciences, and Bavarian agricultural researchers comparing the covered field with an uncovered control plot. Sensors track soil moisture, air temperature, humidity, light, wind, and leaf wetness at different heights and depths.
Early results from the first prototype suggest that extra shade improved soil conditions and helped retain moisture, a practical benefit during the hot, dry weeks of June, July, and August. The second prototype is still being tested, and researchers are also studying an unusually messy problem. Crop sprays can land on the underside of the modules, potentially increasing dirt, corrosion, and efficiency losses.
Germany had 904 hop farms in 2026, including 722 in Hallertau. The number of growers has fallen by more than 40% since 2006 even as the national hop area increased by about 4%, a sign that fewer families are managing larger operations. Germany harvested about 95 million lbs. of hops in 2025, down roughly 7% from the previous year.
Climate pressure adds another layer. A 2023 Nature Communications study found that average Hallertau hop yields after 1995 were 13.7% lower than in the earlier comparison period, while average alpha-acid content fell 15.6%. Its models projected yield declines of 4% to 18% and alpha-content declines of 20% to 31% by 2050, which matters to brewers because alpha acids are a major source of beer’s bitterness and a key measure of hop value.
The United States is moving through a different market cycle, but the pressure is familiar. USDA forecast 41,642 acres of hops strung for harvest in 2026, with Washington accounting for 30,301 acres, down 3% from the previous season. The Brewers Association says planted acreage is nearly 31% below its 2021 peak as the industry adjusts to slower beer sales and high inventories.
Washington researchers have already mapped roughly 87,000 acres of farmland that could plausibly support agrivoltaics near electrical substations, though the state still lacks a large-scale example. Hop fields may offer a useful test because they already depend on tall trellises, but Bavaria shows why this is not a plug-and-play upgrade.
The pilot suggests that panel angle, shade timing, crop quality, grid access, permitting, and maintenance all have to work together.
Wimmer is already planning to expand the covered area from about 12 acres to roughly 49 acres, with a target of 8 megawatts of solar capacity and a 1-megawatt battery. That confidence matters, but it is not the same as a final scientific verdict. The second prototype remains under evaluation, and the project still represents one farm, two hop varieties, and a very specific local climate.
Still, the most valuable result may be the design rule it uncovered, because more shade is not automatically better and maximum noon output is not necessarily the most profitable outcome. The winning system is the one that protects the crop, preserves the cones, and produces power when the market values it.
The official HoPVen project overview was published by Fraunhofer ISE.
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