“Vitivoltaic” projects aim to make viticulture suitable for climate change. The word is a portmanteau of the Latin genus name of grapevine, vitis vinifera, And the term for solar power generation, photovoltaics. This new technology makes it possible to harvest two different cheeses on two levels: power above and wine grapes below. Pilot projects are underway to test which technology works where – and at what cost.
In Germany’s southwestern Ringau region, known for its picturesque vineyards Geisenheim University (HGU) Expertise in all aspects of the wine industry. Here, researchers have created a test facility to determine how the region’s beloved white Riesling can continue to grow with the help of photovoltaic (PV) modules despite changes in climate.
The modules are mounted at a height to make room for vines and agricultural machinery below. This structure provides support and protection to the delicate vines from hail, heavy rain and bright sunlight. When the sun shines, the semi-transparent solar modules form a checkerboard pattern on the ground. A tracking system automatically aligns the modules so they catch every beam of light.
Riesling in danger
“In viticulture, we have not yet seen protected cultivation,” said Manfred Stoll, who leads the university’s general and organic viticulture department. Grapes don’t ripen in greenhouses or under plastic sheets, he said, and the idea of using PV modules to provide passive protection against hail and heavy rain is fairly new.
But climate change means Riesling, Germany’s most popular wine variety, could use some help. The vines now germinate earlier and are highly sensitive to late frost. The grapes are also exposed to more sunlight, and therefore have more sugar and less acidity, which changes the alcohol content and flavor. There are now two vintages of the university’s “Watt Wines”, a Riesling that is light and fruity – just like it used to be.
Using heating wires to avoid frost
Through the project, HGU has also gained abundant experience in the field of microclimate. The €350,000 ($400,000) experimental facility – financed by EU and state funds – uses multiple sensors to measure soil moisture, temperature and light. There was no damage from solar radiation or heavy rain beneath the panels, while the adjacent reference area was severely affected.
Heating wires and drip irrigation hoses are strung along the vine rows. The former proved its usefulness during a three-night frost in late April 2024. The critically endangered seedlings, which were already 10 cm (3.9 in) tall, were heated by wires powered by stored green electricity. Traditionally, wine producers burn large quantities of beeswax candles during the late winter, Stoll said, but the practice is difficult and results in heavy smoke that pollutes the environment.
HGU uses the electricity it produces to control the facility and charge farm vehicles, cars and e-bikes, as well as run pumps and an autonomous caterpillar, a robot that loosens soil, cultivates soil, works undergrowth and applies plant protection products.
“A winery requires energy year-round for production, storage and logistics,” Stoll said.
Vitivoltaic technology is attracting attention as the wine industry grapples with a number of challenges: harvests have been poor in some regions, and changes in consumer habits, tariffs and oversupply have put pressure on the world market. There is a lack of money for investment, even though generating electricity could be another source of income for the winery.
Last year, another, much smaller mobile system made of PV modules was installed in Geisenheim. The modules, attached to existing vineyards like awnings, fold automatically with the help of a small motor in the event of a storm or hailstorm.
The structure is much more economical, but the safety and power yield are lower. Nevertheless, HGU continues to test for optimal solutions because, as Stoll said: “We certainly do not have time to wait any longer.”
abandoned vineyards
Engineer and hobbyist wine grower Christoph Vollmer is also working with photovoltaics. His small vineyard in Oberkirch, southwest of Stuttgart, is difficult to cultivate with agricultural machinery because of its slopes of more than 30%, partly located in terraces.
Vollmer is managing director of Intech Clean Energy GmbH, a family business specializing in agrivoltaics, which has developed a design for such steep slopes, whereby a few glass modules are suspended from steel cables. Vollmer is now installing them in his own vineyards.
The young winemaker wants to plant 2 hectares of robust new fungus-resistant grape varieties under solar panels and produce about 1.5 megawatt hours per year. He is currently negotiating a contract with municipal utility providers for electricity. He also wants to charge an autonomous Caterpillar tractor to relieve tough work on slopes.
Installing photovoltaics at sharp angles is difficult enough, but from an engineer’s perspective it presents an exciting challenge. It’s also a necessary undertaking, Vollmer said. While sun-drenched hills were once a favorite location for viticulture, global warming means it can also be practiced successfully in the less harsh German lowlands.
“Many vineyards have already been abandoned because no one wants to farm them anymore,” he said, adding that more would happen if minimum wages for workers reduced wine producers’ returns. But, he added, the vine-covered slopes are part of the cultural landscape, a tourist attraction and important for the conservation of the species.
Inadequate grid, slow bureaucracy
“With Vitivoltaic, we offer farmers the opportunity to reduce manual labor, harvest healthier grapes, and become profitable. Electricity always has value, especially when PV is combined with storage,” Vollmer said. “Wine producers know they need to take action. We get a lot of enquiries. But often lack of grid connection dampens enthusiasm.”
The length of power lines to be laid, as well as the options for using the electricity produced or selling it directly to local consumers, are important for economic efficiency. But the approval process can be lengthy as energy production changes land use. Only PV systems located a short distance from the farm can be built without a permit. “This severely restricts the market,” Vollmer said.
Vitivoltik in Oberkirch is co-financed by the State of Baden-Württemberg’s research program “Viticulture 4.0” (Viticulture 4.0). Whether such a system, costing several million euros, is worthwhile even without subsidies is a question of grid connection and wine marketing, Vollmer said. In his view, it would be most practical for local businesses to unite as individual plots in viticulture are generally small.
This article was originally written in German.