As the world hurtles toward a low-carbon future, solar energy is rightly being celebrated as a beacon of sustainable progress. Among the most innovative developments in this sector is the rise of floating solar power plants—photovoltaic (PV) panels deployed over lakes, reservoirs, and even sheltered marine zones. Known as floating photovoltaic systems (FPVs), these solar arrays have captivated policymakers and investors alike with their promise: abundant clean electricity without sacrificing precious land.
In India’s ambitious journey toward achieving 500 GW of non-fossil fuel energy capacity by 2030, a quiet revolution is underway—not on land, but on water. Floating solar power plants are rapidly gaining traction as an alternative means to harness solar energy, utilising the surfaces of water bodies to deploy solar arrays in a space-efficient manner.
At first glance, floating solar seems like a win-win. It avoids the land acquisition issues that plague large solar parks, reduces water evaporation, and improves panel efficiency by using water bodies as natural coolants. Leading this movement are flagship projects like the Omkareshwar Floating Solar Park (600 MW) in Madhya Pradesh and the Ramagundam Floating Solar Project (100 MW) in Telangana.
But is the picture as green as it seems?
Beneath the sheen of innovation lies a less visible, but increasingly urgent, environmental debate. Floating solar power plants—while well-intentioned—may be jeopardising the very ecosystems they are installed to coexist with. If deployed without environmental foresight, these “green islands” could prove to be ecological minefields.
A Climate Solution That Could Emit More?
It sounds counterintuitive, but recent research from the journal Environmental Science & Technology (2024) found that floating solar systems deployed in smaller water bodies (less than 5 hectares) can increase emissions of methane and carbon dioxide by up to 26.8%.
When solar panels cover the surface of a lake or reservoir, they reduce sunlight and wind-driven mixing. This change in microclimate decreases dissolved oxygen levels, creating ideal conditions for methane-producing bacteria to thrive. Additionally, the submerged vegetation under the shaded water begins to decay anaerobically, releasing more methane—a greenhouse gas far more potent than carbon dioxide.
While the overall carbon footprint of floating solar systems (approximately 38–55 grams of CO₂ equivalent per kilowatt-hour) remains much lower than that of coal-based power (73–110 gCO₂eq/kWh), these localised emissions are real and must be carefully considered during site selection and project planning.
Thermal Stratification and Underwater Oxygen Crisis
Floating solar panels might reduce algal blooms and evaporation, but their shading effect can have unintended consequences on water quality. Surface water temperatures under FPVs can drop by 1.5–3°C, especially during summer months. This thermal stratification disrupts the natural vertical mixing of the water column, an essential process for nutrient circulation. In turn, this leads to oxygen depletion, a condition known as hypoxia. When oxygen levels fall below 4 mg/L, fish and aquatic invertebrates begin to suffer or die.
A study published in Nature’s Scientific Reports (2023) examined floating photovoltaic (FPV) systems on Lake Maiwald in Germany and found that the installation significantly reduced sunlight (irradiance) reaching the water surface—by approximately 73%—and lowered near-surface wind speed at the height of the solar modules by an average of 23%.
Singapore’s Tengeh Reservoir FPV project is often cited as a model for environmentally responsible floating solar. There, the government implemented real-time monitoring and installed aeration systems to maintain dissolved oxygen levels. Unfortunately, most Indian projects do not incorporate such advanced safeguards.
Biodiversity: The Invisible Cost
Freshwater ecosystems are complex webs of life where light, oxygen, and nutrients interact in a fragile balance. Introducing large FPV systems can tip this balance.
For instance, research has documented a 15–20% decline in fish growth rates in areas shaded by FPVs. The biomass of macrophytes—submerged aquatic plants essential for oxygen production and habitat—is known to fall by as much as 30% when coverage exceeds 70%. Even birds and raptors that hunt over open water are also affected, as are migratory fish whose routes may be blocked by large installations.
In marine environments, the stakes are even higher. Floating structures increase water turbulence, resuspend sediments, and raise turbidity levels, harming coral reefs and benthic organisms. Moreover, these installations can become breeding grounds for invasive species, which use the artificial habitat to outcompete native flora and fauna.
As floating solar moves into estuaries and lagoons—fragile zones with high ecological value—questions arise: Are we trading marine biodiversity for clean energy? And is that a price we are willing to pay?
Leaching, Plastics, and Noise
Another underreported risk of floating solar is chemical pollution. Some older solar panels, especially those containing cadmium telluride, can leach heavy metals if they crack or corrode. Many floats and anchoring materials are made from polymers that degrade over time, releasing microplastics and chemical additives into the water.
Installation and maintenance work also introduces underwater noise pollution, increasing ambient sound levels by up to 20 decibels—enough to disturb fish communication and breeding patterns.
Then there are livelihood and access concerns. Large floating solar projects often encroach upon traditional fishing areas, displace cultural practices, and restrict community access to water bodies, particularly in tribal and rural regions.
India’s Bold but Risky Bet
India is making commendable strides in renewable energy, and floating solar has significant potential—especially in a land-constrained, water-abundant country. The Omkareshwar project alone is expected to reduce carbon emissions by 1.2 million tonnes annually and conserve millions of litres of water through evaporation control.
However, many of these projects are located in tribal belts or ecologically sensitive zones. For instance, the Narmada reservoir, tapped for the Omkareshwar project, supports diverse aquatic life and provides livelihoods to fishing communities. If not implemented with caution, these projects could displace communities, degrade biodiversity, and cause long-term environmental harm.
Researchers emphasise the need for site-specific assessments and environmental impact evaluations as critical tools to guide the sustainable expansion of FPV technology.
Moreover, floating solar projects in India are not yet covered by a dedicated Environmental Impact Assessment (EIA) framework. Unlike large hydro or thermal power plants, FPVs often escape the scrutiny of the EIA Notification, 2006. This regulatory vacuum needs urgent attention.
Filling the Research Gaps
Despite the growing number of FPV projects, long-term studies on their environmental impact are scarce, especially in tropical regions. We still lack:
* Reliable data on ecological and chemical impacts
* Guidelines for sustainable design and deployment
* Monitoring systems to track seasonal changes in water quality and biodiversity
There is also no protocol to assess the cumulative impact when multiple reservoirs in the same watershed are converted into FPV sites.
Without this information, we risk deploying floating solar in a data vacuum—flying blind in the face of complex environmental challenges.
What Can Be Done?
The good news is that many of the risks associated with floating solar are avoidable or manageable—if addressed early.
* Coverage Limits: Coverage should not exceed 70% of the water body’s surface area, and ideally should stay below 30% in biodiversity-rich or ecologically sensitive regions.
* Eco-Responsive Design: Newer FPV designs allow wind and sunlight to pass through, or rotate with the sun to avoid constant shading. These innovations reduce ecological disruption.
* Material Safety: All components must be tested for water safety, leach resistance, and long-term durability. Avoiding PVC-based floats and corrodible metals is critical.
* Real-Time Monitoring: Temperature, dissolved oxygen, turbidity, and nutrient levels should be continuously monitored using sensors. This data must be shared transparently with local authorities and communities.
* Public Participation: Fisherfolk, tribal leaders, and local communities must be involved in the project planning stage—not just informing afterwards. Their knowledge and rights are integral to long-term sustainability.
* Stronger Regulation: India urgently needs a national guideline for FPV environmental assessment. This should be part of the Central Electricity Authority’s regulatory toolkit and embedded into state-level renewable energy policies.
Exploring Alternatives: Canals and Highways
While floating solar offers unique advantages, India should also explore alternative deployment models that avoid ecological conflict altogether. One promising option is the installation of solar panels over existing canals and highways. Gujarat’s canal-top solar project, for example, not only generates clean energy but also prevents water loss through evaporation and makes efficient use of otherwise unused infrastructure.
Highways and roads can be similarly repurposed. Solar panels over roads do not disrupt aquatic life and can even provide shade that extends the lifespan of asphalt. These spaces are linear, already disturbed, and often closer to transmission infrastructure, reducing energy loss in transit.
Scaling up such land-neutral solar options would help reduce the pressure on sensitive water bodies while still contributing significantly to India’s renewable energy goals.
Let’s Not Repeat the Mistakes of the Past
Floating solar has the potential to become a key player in the fight against climate change. But as with any large-scale intervention, its success hinges on one thing: balance.
If we are serious about sustainability, we must ensure that floating solar power does not come at the cost of freshwater health, aquatic biodiversity, or rural livelihoods. Clean energy should not dirty our rivers, lakes, or coastal waters.
We cannot afford to repeat the mistakes of the past, where development outpaced ecological wisdom. Floating solar must float not just on water—but on principles of precaution, participation, and long-term ecological stewardship.
When deployed responsibly, FPVs can offer a sustainable energy solution that powers the planet while safeguarding natural ecosystems. However, if ecological concerns are overlooked, they risk becoming yet another example of greenwashing with gray consequences. Without careful consideration, we may realise too late that the true cost of clean energy has been borne by the very ecosystems we intended to protect.
Views expressed are personal. The writer is Head-Think Tank, Mobius Foundation, New Delhi
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