Floating solar systems cause greenhouse gas emissions
Building solar systems on the water reduces land use. However, floating PV also has its downsides – in the literal sense.
Construction of a floating PV system for the Cornell study
(Image: Jason Koski/Cornell University)
Floating photovoltaic (PV) systems are considered a good alternative to solar systems on land because they do not consume land that could otherwise be used for agriculture, for example. However, a recent study from the USA shows that these systems have a negative impact on the environment.
This is because the PV systems generate clean electricity. But they cause greenhouse gas emissions, as Steven Grodsky's team found out. For the study, which was published in the journal Environmental Science & Technology, the researchers covered six ponds, each measuring 30 by 30 meters, with PV systems in the summer of 2023. The PV systems covered around 70 percent of the water surface.
Videos by heise
Over a period of more than a year, the researchers observed the development in the covered ponds compared to those whose surface remained free. This showed that overbuilding has a major impact.
Floating PV systems interfere with ecological processes
“If you build floating solar plants, you drastically reduce the availability of oxygen for the organisms,” says Grodsky. “You interfere with ecological processes, the way decomposition takes place, the microbes, the way the wind sweeps across the surface of the water. It's all connected.”
The first effects became apparent after just a few days: the temperature dropped and the oxygen content in the water became lower, especially at the bottom. These changes affected the aquatic plants and the microbial decomposition at the bottom of the water.
Methane is produced there, which rises in the form of bubbles and is released into the atmosphere. The team found that emissions of the greenhouse gases carbon dioxide and methane had risen sharply by almost 27 percent compared to ponds without solar panels.
It was known that the overbuilding of PV systems has an impact on bodies of water. In Germany, for example, only 15 percent of the water surface may be covered by solar systems. There have already been studies on this, says Grodsky. However, these were “mostly modeling and projections”. This is the first empirical study. “It tells us what is actually happening.”
In the researchers' view, however, this does not fundamentally speak against floating PV systems. For example, the total emissions per kilowatt-hour of energy generated are probably lower than those of solar systems on land. In addition, the effects could be reduced by using less water surface area, by arranging the panels differently or by installing circulation systems.
(wpl)
