A project in Germany testing the agrophotovoltaic (APV) concept has shown a land use efficiency of 160% in 2017 and as much as 186% in 2018, the Fraunhofer Institute for Solar Energy Systems ISE said Friday.
The “Agrophotovoltaics – Resource Efficient Land Use (APV-RESOLA)” project evaluated the benefits of producing both solar power and crops on arable land near Lake Constance. The partners in the project installed a solar system of 194 kW on a five-meter-high structure on land used to grow winter wheat, potatoes, clover and celery. Land use efficiency was very high in 2018 because the partial shading provided by the PV panels helped boost the agricultural yield in the very hot summer. Solar power generation also grew because of the abundance of sunlight.
In 2018, the yields from three of the four crops grown under the panels were above the reference yield. For celery and winter wheat the project showed gains of 12% and 3%, respectively, compared to the reference, while for clover there was a reduction of 8%.
“We can assume that the shade under the semi-transparent solar modules enabled the plants to better endure the hot and dry conditions of 2018,” agricultural scientist Andrea Ehmann explained. Her colleague Axel Weselek said that the project confirms the potential for APV in arid regions, while calling for trials in other climate regions and with other types of crops.
Solar irradiation beneath the PV system was roughly 30% less than the reference field. In spring and summer, the soil temperature was lower than on the reference field, while the temperature of air remained the same. In the hot and dry summer, the soil moisture in the wheat crop was higher than the reference field, while in the winter months, it was lower.
Fraunhofer ISE is already working on several projects to bring the APV concept to threshold and developing countries, as well as to find new applications. It said cutting evaporation has helped achieve up to 40% higher yields for tomatoes and cotton crops in a project in the Indian state of Maharashtra.
Besides reducing evaporation and helping lower temperatures, PV modules can also help harvest rainwater. At the same time, in order to make agriculture even greener, the solar power produced by APV systems can be used to charge electric vehicles (EVs), whose use at farms is growing. Fully battery-electric operated tractors are already available.
Financing for the APV-RESOLA project came from the German Federal Ministry of Education and Research and FONA. Fraunhofer ISE partnered in it with BayWa re Solar Projects GmbH, Electrizitaetswerke Schoenau, Demeter farm cooperative Heggelbach, Karlsruhe Institute of Technology, Regional Association of Bodensee-Upper Swabia, and the University of Hohenheim.