Agrivoltaics – solar panels on top, potatoes down below

Germany is planning on using renewables to cover 65 percent of its power consumption by 2030. In order to hit this target, new powerful solar farms will need to be built – not least because the expansion of wind energy in rural areas has ground to a halt. But land is considered a commodity in central Europe. So, what can we do to make sure solar energy does not have to vie with industries such as agriculture? One approach being considered across the world is referred to as agrivoltaics: Photovoltaic modules generate electricity from above, and vegetables grow underneath.

Solar modules five metres above ground

The Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg is Europe’s largest solar research institute. Since 1981, the institute has been working to identify future solutions for the energy transition, both in the laboratory and in real life. One of its projects is an agrivoltaic plant in Herdwangen-Schönach, around 30 kilometres north of Lake Constance, where a 2,500-square-metre pilot plant has been in operation for three years on the Demeterhof farm of the Heggelbach farming community.

The solar modules, with an output of 195 kilowatts, generate electricity on five-metre-high steel structures, so tractors and combined harvesters can easily fit underneath. Over the past three years, farmers have used the fields to grow winter wheat, potatoes, celery, grass and clover leys under the steel structure. According to ISE, the participants were generally satisfied with the quality of harvest in the first two years – despite the lower yield, which was attributable to the fact that the panels let less light through. Despite the smaller crop, the efficiency of land use is increased by 60 percent, according to the calculations of the Fraunhofer ISE and the APV-RESOLA innovation group.

Perfect for small spaces 

“Agrivoltaics make sense wherever in the world land is at a premium,” says Tabea Obergfell, a geoecologist at Fraunhofer ISE. And such land-use conflicts occur in various densely populated countries, such as Germany. “If we were to use 1-2 percent of the arable land in Germany for two purposes with the help of agrivoltaics, that would be great. It would bring us much closer to our goal of using renewables to cover more than half of the electricity we need by 2030.”

The researchers at ISE in Heggelbach are satisfied with the electricity production costs, which are currently around 9 cents per kilowatt hour and cover investment budgets as well as operating and maintenance fees. This means agrivoltaics are cheaper than private roof-mounted systems, but more expensive than ground-mounted PV arrays. 

Outlook for farmers

In Germany, subsidies have so far either been allocated to agriculture or photovoltaics. However, agrivoltaics is not supported via the PV Power Tender Regulation (PV-Freiflächenausschreibungsverordnung) or by the EEG Feed-in Remuneration Programme (EEG-Einspeisevergütung). As such, it is not yet possible to operate such plants economically.

“Many small farms have had to throw in the towel, while larger, energy-intensive businesses soldier on. You have to be economically efficient in order to remain competitive. To survive, many farmers prefer to turn to generating electricity rather than growing crops. Until now, this has been an either-or-decision due to land-use conflicts,” explains Tabea Obergfell.

The research project in Heggelbach has now come to an end but the plant has remained operational. The farm community can cover their own consumption using self-produced electricity and they are even able to feed electricity into the local grid. Every year, they generate enough electricity to cover the power demands of 62 families of four.

Best suited for hotter climates

In very hot regions with high levels of solar radiation, agrivoltaics make a lot of sense because plants that thrive in the shade can grow better with the help of this technology. Areas that are drier with little to no wind can also benefit. The AgroPV-Chile project, which is being conducted by the German Fraunhofer ISE in collaboration with the Chilean Fraunhofer Centro de Tecnologías para Energía Solar (CSET), has been running for the last three years. According to the Fraunhofer ISE, the results of both the agricultural production side of things as well as from a solar power generation perspective are very positive. This means the research efforts will be stepped up further.

According to ISE, the potential benefits agrivoltaics have for the dry and semi-arid regions of northern and central Chile are estimated to be manifold, since large parts of the population support themselves through agriculture and are, as such, affected by drought, desertification and water shortages. As the solar panels cast shadows on the land below, agrivoltaic systems have been shown to reduce the need for water whilst also providing shade for farm animals. Even plants that would not be able grow in strong sunlight can be cultivated within an APV system, and the electricity produced can be used to supply local farms and villages.

World’s largest solar plant makes land usable

Agrivoltaic technology has so far mainly been used within a global research setting. However, it is already receiving government funding in France, Japan and China.

The world’s largest solar farm with an output of around 700 megawatts is in fact an agrivoltaic plant, located on the edge of the Gobi Desert in China, where the land below was not originally usable for agricultural purposes. Today, berry bushes grow under the shady solar panels. The groundwater is extracted with the help of the generated power, and the plants are watered with the droplets.

Since the Fukushima disaster in Japan, swathes of once arable land have been contaminated with radioactivity. Although the uppermost contaminated soil layers have since been removed, the fertile humus was also lost as a result. By installing agrivoltaic plants on the rice fields, farmers are now better able to support themselves financially with the income earned from the solar power system instead of relying solely on rice cultivation.

It’s a question of politics

This method of co-developing land using agrivoltaic systems is well-suited to very sunny countries or nations where land comes at a premium. When she thinks of all the plants that are already operating across the world, Tabea Obergfell also remains hopeful for Germany. “Politicians seem to have not yet grasped that we have actually managed to launch a whole new technology here,” she says. Politicians will have to pave the way to ensure that agrivoltaics can become part of the energy transition.