German coal mines could play host to as much as 56GW of floating solar

German research institute Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) has calculated Germany’s lignite open-cast ponds could host as much as a technical capacity of 56 GW of floating solar PV, but a more realistic economic potential of 2.74 GW.

The research carried out by Fraunhofer ISE, conducted on behalf of German clean energy construction company BayWa re, analysed the technical potential of installing floating solar PV projects atop the artificial lakes of lignite open-case mines across Germany.

The country’s lignite mining industry created almost 500 open-cast ponds with a total area of ​​47,251 hectares – most of which are in the state of Brandenburg (29.8%), Saxony-Anhalt (28.2%) and Saxony (15.7%).

A total technical potential of 56 GW was estimated, but after excluding areas relevant for leisure activities, tourism, nature, and landscape protection, the Fraunhofer ISE team arrived at a total economically exploitable capacity of 4.9% of the total, amounting to around 2.74 GW.

“Floating PV power plants are a relatively new concept for the use of photovoltaics, but for which there is great potential for generating electricity worldwide, not least because they allow for a neutral expansion,” explained Dr Andreas Bett, Director of Fraunhofer ISE.

Floating solar PV development is particularly important in Germany which has limited agricultural area available for traditional solar development, requiring land-neutral solutions to be developed.

Floating solar PV also has its own technical benefits, beyond the natural constraints of countries like Germany and Japan, such as lower operating temperatures due to being situated on water. Open-cast ponds also provide benefits for floating solar PV, considering they are already well connected to the national grid network.

Germany’s potential for floating solar PV is also well in excess of that which was highlighted in the Fraunhofer ISE report, considering only lignite open-cast ponds were assessed, excluding other artificial water types such as natural stagnant water and ponds over retired construction material mines.

In fact, with 4,474 artificial bodies of water across Germany – including 725 dredging lakes and 354 gravel lakes – floating solar PV projects could play a vital role in Germany’s solar PV expansion of 500 GW required for the country’s energy transition.

However, electricity generation costs of floating solar PV projects are on average 10% to 15% higher than those of traditional solar PV projects, requiring greater investment costs, leading Fraunhofer ISE researchers to conclude that some measure of policy support would be important.

“Therefore, it would make sense to have innovation tenders especially for FPV and other area-neutral PV power plants that still need a market boost,” said Dr. Harry Wirth, Head of Photovoltaic Modules and Power Plants at Fraunhofer ISE.

“In order to avoid time-consuming changes to the land use plan, the land-neutral FPV should be privileged, similar to what is already planned for the use of land for wind and nuclear power.”

The researchers also recommended that open-cast lakes be classified as conversion areas under German renewable energy law, and that floating solar PV projects should be an option as part of the renovation framework plans for former open-cast mines.