Home – Energy – Scientists heard birds calling from under a floating solar farm in the Netherlands, and what is nesting beneath the panels changes how they get built
Solar panels are supposed to be quiet. Yet at Bomhofsplas, a large floating solar farm near the Dutch city of Zwolle, researchers heard birds and ducks beneath the array, suggesting that the sheltered space may be used for resting or even nesting. Below the waterline, another community was taking shape.
A monitoring program carried out from 2020 through 2023 found 431 fish and 1,951 invertebrates using 20 artificial underwater habitats known as “Biohuts.” The finding does not prove that every floating solar plant helps nature. It does show that careful engineering can make an energy project function as habitat as well as infrastructure.
The bird observation came during a 2021 water-quality study at the site. Researchers saw birds on the platforms and between the modules, then occasionally heard birds and ducks beneath the floating structure. They wrote that this suggested the animals were using the protected space to rest and build nests, although the team did not report directly inspecting or confirming nests.
That is not entirely good news, though. The same researchers found heavy bird droppings on the section closest to open water and warned that the waste could reduce panel efficiency and add nutrients to the lake after rain, which led the operator to test an ultrasonic deterrent in that area.
The stronger ecological evidence came from the water. Ecocean installed 20 Biohuts in three zones of the solar park and monitored them during three surveys between 2020 and 2023. These cage-like structures are designed as artificial nurseries where young fish can hide while microorganisms and invertebrates colonize the surfaces.
Across the monitoring campaigns, the team recorded 2,382 individual animals. That total included 431 fish and 1,951 invertebrates, with common perch, cyprinids, a tubenose goby, gammarids, freshwater snails, zebra mussels, and freshwater sponges among the organisms observed.
Those numbers matter because the smallest residents help support everything above them in the food web. Daphnia, gammarids, and other tiny animals become prey for fish and larger species, while the Biohuts give juveniles cover in parts of the lake that otherwise offer little protection. By 2023, Ecocean said the number of species may have been approaching a peak.
Bomhofsplas is not a pristine natural lake. It is a former sand-extraction pit, which made it a more suitable testing ground than a sensitive wetland or protected water body. The floating installation covers about 45 acres, contains roughly 73,000 panels, and has a rated capacity of 27.4 megawatts peak, enough to supply the equivalent of about 8,000 homes.
Design choices appear central to the result. The array is anchored to the lakebed instead of the shore, reducing disturbance around the banks, while spaces in the structure allow some wind, water movement, and sunlight to pass through. In practical terms, the project did not simply place a dark lid over the lake.
Floating solar can also reduce evaporation by shading the water. The water may help moderate panel temperatures and improve output, although the size of that benefit varies with weather, module design, and airflow. That is useful during sticky summer heat, but it is not a guaranteed performance boost everywhere.
For the 2021 study, researchers placed sensors beneath the array and at a reference point in open water, then used an underwater drone to examine conditions at different depths. They found broadly similar values for key water-quality measures and reported no major differences in temperature or dissolved oxygen. Underwater images also showed biofouling and small bivalves colonizing the floating blocks within months.
Still, the authors were careful about the limits. Their work was an initial screening at one artificial sandpit using one particular floating design, not a complete ecological verdict on all lakes. They also said longer monitoring, biological measurements, chemical analysis, and data collected before construction would be needed to understand the full impact.
The question is becoming more important as floating solar expands. An International Energy Agency Photovoltaic Power Systems Programme review reported that global installed floating-PV capacity reached 7.7 gigawatts by the end of 2023, up from just over 1.6 gigawatts at the end of 2018. But the same review said limited long-term data and the absence of mature regulatory frameworks still create uncertainty.
Bomhofsplas offers a practical lesson for developers. Habitat features, spacing, mooring, light penetration, and ecological monitoring cannot be treated as decorative extras added after construction. At the end of the day, what the project suggests is simple. The environmental outcome depends to a large extent on how the system is built and where it is placed.
The sound of birds beneath the panels is intriguing, but the measured fish and invertebrate counts are the firmer evidence. For now, Bomhofsplas is best understood as an encouraging case study, not proof that covering water with solar panels is automatically harmless.
The project findings were published by Ecocean.
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