Renewable energies: double the harvest using photovoltaics

A group of researchers, farmers and climate advocates is calling for the expansion of photovoltaic use. Because solar cells over fields and orchards can enhance energy transfer – and give farmers a “second harvest”.

By Lena Potvarkin, SWR

The expansion of renewable energies in Germany must happen much faster than before – that was only recently Opinion of the Expert Council on Climate Issues Shown. In addition to wind energy, photovoltaics are a promising part of Germany’s energy transition. annoying Calculations of the Fraunhofer Institute for Solar Energy Systems (ISE) Five to seven times as many photovoltaic systems as are required today to create a climate-neutral power system in Germany by 2045. But when it comes to expansion, there are always conflicts about land: Should an empty area be used for agriculture or for solar energy?

“Great potential for energy transition”

An alliance of the association Agriculture Connects Germany, the climate protectors of Parents for the Future and the think tank Jülich is now calling for the combination of the two and so-called photovoltaics to expand more quickly. So solar energy systems over fields, pastures and orchards. The technology offers “significant potential for the post-fossil energy transition,” and therefore must be funded more aggressively by the federal government and speed up the approval process.

A research project at Fraunhofer ISE is currently working on exactly how to produce food and electricity at the same time. Depending on what is being grown in the fields, the solar modules are placed between or on top of the plants. in one guidance Fraunhofer ISE assumes that all crops are basically suitable – albeit with different effects on yield.

Good for orchards, vineyards…

In fruit growing, photovoltaics can offer advantages, explains project manager Maximilian Tromsdorf. Because highly fitted systems can provide protection: from the sun and heat, but also from cold, frost and heavy rain. Particularly heavy rains are becoming more common in Germany due to climate change, according to data from the German Weather Service. “In so-called gardening, we see high-tech synergy potential for agricultural photovoltaics,” says Tromsdorff.

In Germany this has so far been tested in apple cultivation, for example in Gelsdorf in Rhineland-Palatinate. Photovoltaic agricultural systems can also be envisioned in viticulture. The modules will then be placed on the rows of vines. This is already being implemented in France, but not yet in Germany. “The advantage of this is that long-term crops are grown here, so the PV system can be well adapted there,” says Tromsdorff.

…difficult in farming

On the other hand, in arable farming, you have to adapt the PV system to crop rotation in the fields, not to a single plant. The fields provide the largest area for photovoltaic systems. In concrete terms, this means that the systems are positioned above the fields, high enough to drive the large machinery below. However, shadowing reduces yield – the goal is to position systems in such a way that a maximum loss of 20 percent can be expected.

So far, potatoes, wheat and other types of cereals have been tested. In principle, corn can also be conceived, but not necessarily in temperate climates such as Germany, because the corn plant needs a lot of light to grow. In the south, however, photovoltaics can be useful when available light is not the problem, but weather phenomena such as heavy rain impede growth.

High costs as a sticking point

The The University of Hohenheim recently calculated in a studyOne percent of Germany’s arable land could cover nine percent of electricity needs. Photovoltaics will thus be part of the German energy transition. The study estimates that ten percent of farms in Germany should participate.

However, this could result in costs of €1.2 billion annually – because the installation of photovoltaic systems is more complex than conventional solar panels. The high cost is also the biggest criticism of the technology. It has been possible, at least recently, to promote agricultural photovoltaics through the Renewable Energy Sources Act (EEG). However, says project manager Tromsdorff, smaller systems are currently considered a disadvantage in EEG – but in particular they have other advantages in addition to producing electricity, for example in growing fruit.

years of approval process

Another hurdle is currently the approval process. Trommsdorf worries that waiting several years for planning permission before starting a project may discourage interested parties. Faster operations can also help attract more growers.

In principle, Tromsdorf believes enough companies can be found for photovoltaics. “But you could say there are significant differences between the applications,” he says. “People are more skeptical about farming than they are about gardening, for example, because using their large farm machinery can get more complicated.”

The scene changes

In addition to farmers, local residents will also have to approve photovoltaics. After all, the landscape can change dramatically due to large systems.

In principle, most Germans are in favor of an energy transition, according to one Survey from 2020 89% find the greater expansion of renewable energies at least important. In order for projects to be accepted locally, transparency and participation are also important, and citizen involvement in the process.