The solar farm Sekdoorn near Zwolle in the Netherlands. Copyright: BayWa r.e.
The Fraunhofer Institute of Solar Energy Systems ISE has investigated the technical potential of floating photovoltaics (FPV) on pit lakes in former lignite mines in Germany. The study estimates a potential PV capacity of 56 GWp for installations on pit lakes. After subtracting the estimated area use for recreational activities, tourism, nature and land conservation on pit lakes, there remains an economical potential of 2.74 GWp.
“Floating PV (FPV) power plants are a relatively new concept, which holds a large potential for electricity generation worldwide, not least because it allows a land-neutral expansion of photovoltaic capacity,” said Dr. Andreas Bett, director of Fraunhofer ISE. The PV modules and, in most cases, the inverters are installed on floating devices that are anchored either on the shore or the lake bottom. A large advantage of FPV is its high land-use efficiency (1.33 MW/hectare). The water on which the PV array floats also provides cooling which results in somewhat higher energy yields. Former lignite opencast mines are good locations for FPV since a connection to the grid already exists. The electricity generation costs for FPV systems are about 10 to 15 percent higher than the costs for conventional ground-mounted PV power plants.
About 500 pit lakes from lignite mining exist in Germany, covering a total area of 47,251 hectares. From the theoretical potential of 56 GW, researchers subtracted areas for recreational activities, tourism, nature and land conservation, while pit lakes smaller than one hectare, with large fluctuations in depth or lacking possibilities for anchorage on shore were rejected for reasons of costs. Conclusively the realistic economic potential was determined to be about 4.9 percent of the theoretical lake area, equivaling an installed power of 2.74 GWp. Other types of artificial bodies of water or natural lakes were not considered in this study, so that the total potential is probably much larger. In all, Germany has 4474 man-made lakes, including 725 quarry ponds and 354 gravel lakes.