A Dutch floating solar project’s shadow has been affecting the water and vital algae.
Harnessing the power of the sun has been key to the global transition away from polluting fossil fuels.
When installation space on land became limited, creating floatable designs seemed like the next natural step in green energy.
But then the water began changing color, raising the question: Will it affect other floating plants in the future?
How solar power triggered a land rush
Many years ago, tapping sunlight for electricity was seen as a niche technology.
Solar panels were expensive to manufacture and accessible to a limited market that could afford them.
However, the climate crisis made it clear that the world had to make a change sooner rather than later.
These days, solar technology is more affordable than new fossil fuel and nuclear power plants. This was due to technical advancements and massive production scale.
By the end of 2024, solar energy was the fastest-growing electricity source in the world.
In that year alone, solar expansion increased by 32% compared to the year before.
Unfortunately, the race toward “Net Zero” and rapid installation soon faced a physical constraint, namely, space.
For many densely populated regions, land is a precious asset not easily given up for utility-scale solar farms.
Local opposition and zoning restrictions also tightened, forcing engineers to look elsewhere.
The move toward the blue horizon
In the latest innovation to overcome the land-use dilemma while ensuring stable power, “floatovoltaics” (FPV) was born.
Soon, nations realized that placing solar arrays on man-made bodies of water was the way forward to generating clean electricity. Irrigation ponds, lakes, and industrial basins soon became the permanent homes of FPV.
Beyond addressing the land competition issue, floating solar also offered other immediate benefits.
On land, the panels tend to overheat, which decreases efficiency and output. Floating plants benefit from the cooling effect of water and also reduce water evaporation, which is essential in drought-stricken areas.
Given that this approach is still relatively new, floating solar projects also present opportunities to analyze potential environmental impacts.
In the Netherlands, a sun-tracking floating solar project on Rotterdam’s Kralingen reservoir piqued researchers’ interest.
It turns out that the shadow cast by solar panels can have a negative effect on water.
Floating solar: Blue-green water rises from the shadows
Large-scale floating solar plants generate record energy, but they also have a hidden cost that depends on water depth.
The Kralingen reservoir is fairly shallow, with an average depth ranging from 13 to 16 feet.
Before the panels were installed, sunlight could easily penetrate the clear water to reach the floor. This is essential for supporting lush meadows of green algae (Chara), often called stonewort.
They keep the reservoir healthy by anchoring sediment and ensuring the water is clear and oxygenated.
Researchers from Evides Water Company discovered that the water changed after the floating arrays were installed. The findings are in the study “Illuminating the Impact of a Floating Photovoltaic System on a Shallow Drinking Water Reservoir: The Emergence of Benthic Cyanobacteria,” published in MDPI.
An opportunistic inhabitant altered the water quality
As the algae vanished, benthic cyanobacteria took over, thriving in the shadows.
The bacteria release harmful cyanotoxins and compounds such as geosmin. Water becomes blue-green and has a musty taste that is difficult to filter out.
These floating panels also became breeding grounds for Dreissena mussels, and biofouling further impacts water quality.
The study’s insights show that there is a fine line regarding the extent to which renewable energy is completely sustainable.
Project developers and water managers should carefully plan the layout of FPVs in shallow water and monitor light levels.
This is especially vital when drinking water resources are utilized, as global freshwater is becoming scarcer.
