The joint project “Agrophotovoltaic – Efficient Land Use Resource” (APV-Resola) has been testing solar power production and agriculture, in an efficient way, on the same area for more than two years. Solar modules with an output of 194 kW were installed at a height of five meters above a 0.3-hectare field on Lake Constance (German: Bodensee). In the first project year 2017, the project consortium headed by the Fraunhofer Institute for Solar Energy Systems (ISE) has already demonstrated an increase in efficient land use to 160 percent. This result was again significantly exceeded in 2018.
As the Fraunhofer ISE reports, the partial shading among the solar modules increased agricultural yields in the hot summer of 2018, while the high solar radiation boosted solar power production. As a result, land use efficiency was 186 percent, as the researchers calculated.
Farmers record higher yields
Farmers of the Demeter farm community Heggelbach recorded higher yields of three of the four cultivated crops (winter wheat, potatoes, clover grass, celery) under the APV-Resola plant than on the reference area without solar modules. Celery benefited most (+12 percent), while winter wheat gained 3 percent and clover a minus 8 percent. “In terms of potatoes, the land use efficiency increased by 86 percent per hectare,” emphasizes project manager Stephan Schindele from Fraunhofer ISE.
We assume that the plants coped better with the drought-induced heat summer of 2018 due to the shading under the semitransparent solar modules.
Monitoring microclimatic conditions
In addition to stock development, yield and yield quality, scientists from the University of Hohenheim also collected data on the microclimatic conditions underneith and next to the APV-Resola plant. The photosynthetic solar radiation under the APV system was about 30 percent lower than on the reference surface. In addition to solar radiation, the PV modules primarily influenced precipitation distribution and soil temperature. The soil temperature under the panels was below that of the reference surface in spring and summer, while the air temperature was identical. In the hot and dry summer months of 2018, the soil moisture in the wheat stock under the PV panels was higher than on the reference area. In the winter months and other cultures, however, it was lower.
Better numbers despite extremely dry summer
“We assume that the plants better cope with the drought-induced heat summer of 2018 due to shading under the semitransparent solar modules,” says agronomist Andrea Ehmann. “This also illustrates the potential of the APV for dry regions, but also the need for further experiments in other climatic regions as well as with additional crop species”, adds her colleague Axel Weselek.
Agrophotovoltaic brings synergy effects for agriculture
The solar irradiation in 2018, at 1,319.7 kWh per square meter, was 8.4 percent above the previous year. This increased the solar power production in the crop year 2018 by two percent to just under 250 MWh, which corresponded to an “exceptionally good” specific yield of 1,285.3 kWh per installed kilowatt peak. With electricity generation costs per kilowatt-hour, electricity from an agro-photovoltaic system is already competitive with small PV rooftop systems, and researchers are also counting on falling costs due to learning and scaling effects.
Agro-fotovoltaïsche installatie nu al concurrerend met kleine PV-opdaksystemen.
Increase in electricity demand
If the solar power is stored and used directly on site, as in the case of the Heggelbach farm community, additional sources of income are created for farmers through synergy effects. The use of electric vehicles is also gaining
“If policy permits, agro-photovoltaic can be the answer to the tank-or-plate discussion, because technically, farmers can do both by serving twice arable land in their core food production and by contributing to solar power to expand electromobility and protect the climate, “says Schindele.
Technology offers potential for dry land
In a project within the framework of the EU program Horizon 2020, the Fraunhofer researchers and their partners in Algeria are examining how the APV systems affect the water balance. In addition to reduced evaporation and lower temperatures, rainwater harvesting with PV modules also plays a role.
The project APV-Resola is funded by the Federal Ministry of Education and Research and FONA – Forschung für nachhaltige Entwicklung (Research for Sustainable Development). It is a joint project of Fraunhofer ISE, BayWa r.e. Solar Projects GmbH, Elektrizitätswerke Schönau, Hofgemeinschaft Heggelbach, Karlsruhe Institute of Technology, Regional aliance Bodensee-Oberschwaben and the University of Hohenheim. (Post picture: BayWa r.e.)
Add a wind turbine to your energy generation
For the electricity needed during the winter months, a private wind turbine at an agricultural company is ideal. Wind turbines produce the most electricity in the winter, whereas solar panels do this in the summer. Together they make the ideal combination to provide an agricultural company with electricity all year round. Especially in regions with sufficient wind, generating wind energy is much cheaper than storing solar energy in batteries.