An organic fruit grower from Gelfingen in Switzerland is experimenting with the installation of solar panels above his raspberry crop to see if viable production can be maintained with around half the usual amount of light.
The solar raspberry plantation, which has just been completed, will bring the total photovoltaic (PV) capacity installed by Heinz Schmid to 500kW. The concept, known as agri-PV, is already more established in countries such as Japan, where about 180 different crops are being grown on more than 3,500 sites.
As many soft-fruit plantations and orchards in Switzerland are already fitted with rain roofs or hail protection nets, it was felt that the PV panels could provide similar benefits, while also producing renewable energy. According to those involved in the project, there is also evidence that the micro-climate under the modules can be better controlled. For example, less moisture means fewer diseases, lower temperatures when the weather is hot lead to more yield.
The first system, which was developed by Heinz Schmid himself, features solar panels suspended vertically on wire cables above the plants, with a film underneath the modules to protect the crop from rain. The vertical orientation is primarily intended to take advantage of the morning and evening sun. “This solution is probably the most cost-effective of the three methods used,” explains Heinz Schmid.
In the second system, he uses technology from Swiss start-up Insolight. Steel beams are sunk 1.80m deep into the ground and support the special solar modules at a height of 3.5m. Only about half of the modules are equipped with solar cells and therefore allow enough light through for cropping, with a basic shading level around 50%. The system is equipped with sensors that feed sophisticated software with data. “For example, once the light saturation point for the plant has been reached, photosynthesis no longer occurs,” says Heinz Schmid. At such moments, the screen closes under the modules so that they can optimally use the reflected light to produce additional electricity. The production of high-quality raspberries must always be the priority,” he adds. “There is a risk that external investors in agri-PV will focus too much on selling the electricity. The limited area is used optimally for food and energy production without damaging the soil.”