Agri-PV systems: How photovoltaic panels influence fruit crops

This was shown by the first results at the Haidegg fruit and wine growing experimental station in the state of Styria, which has been testing an agricultural PV system for two years. “Climate change brings more of everything – hail, heat, frost, dry periods,” said Leonhard Steinbauer, head of the station. The areas are also used for food and energy production.

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Test facility on 5,000 square meters

Apples, cherries, apricots, plums – seven types of fruit grow under 1,134 photovoltaic modules on around 5,000 square meters in the east of Graz. These are 49 percent translucent and therefore have a slightly lower performance. In order to be able to compare the effects of the PV system on yield, fruit quality and plant health, the same types of fruit were grown in parallel in the open air, sometimes under hail nets. After the late frost in April, it now becomes clear that in the stone fruit rows without a roof there are brown, dried leaves and hardly any fruit to be found in mid-May. The espalier trees under the solar cells were significantly larger and were already bearing some small fruits.

“Trees stay healthier and grow longer”

“Photovoltaics ensure that the trees stay healthier and grow longer in autumn,” explained Steinbauer. It has been shown that those under the PV structure formed more and higher quality flower buds. It is too early to say how well the modules were able to protect against the frost in April: “We don’t know what happened in the fruit tissue. But things are looking spectacularly better at the moment,” said Steinbauer confidently. In any case, it has already been noted that it is around 0.25 degrees Celsius warmer under the PV system. This is due to the carport effect – like cars under a deck, the temperature under the panels is slightly higher.

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The PV roofing also protects the fruit crops from rain. Figures from Haidegg show that the duration of leaf wetness per day is significantly shorter under the modules. This means that chemical protective agents against fungi, such as those used in organic farming, can be dispensed with. “If the leaves are wet, that is ideal for the scab fungus, for example. It can destroy entire harvests,” says Steinbauer. The panels are arranged in rows above the plants. In between, rainwater comes through and runs through the slope of the slope to the trees.

Hail and mildew as a challenge

According to Steinbauer, hail is one of the challenges: “The grains bounced off the PV modules like a pool table and flew into the next row onto the plants.” Nets between the rows could provide additional protection. “And powdery mildew feels very comfortable here.” They now want to develop solutions against this fungal disease that affects dry leaves.

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“The first focus for photovoltaics remains on pre-polluted areas such as roofs, parking lots or streets,” said Franz Grießer, head of the Agriculture and Forestry Department of the State of Styria. “Through Agri-PV we can secure ourselves not only in terms of nutrition, but also in terms of energy,” he emphasized. Energy production provides a second source of income for farmers.

385,000 kilowatt hours of electricity

The system, financed by the federal and state governments, produces around 385,000 kilowatt hours of electricity per year, which is mainly used locally in Haidegg. It was built by the Ecowind company and went into operation in June 2022. Research will continue in the coming years to develop a sustainable biostrategy. The financing for an expansion of the facility has already been secured by the state of Styria, said Steinbauer. Agri-PV is not suitable for all fruit farmers; it requires suitable infrastructure such as cables.