Study Reveals Increased Greenhouse Gas Emissions from Floating Solar Panels

Floating solar—an innovative method of placing solar panels on bodies of water—has quickly become an exciting new frontier for renewable energy. This technology promises to generate power while potentially avoiding impacts on terrestrial ecosystems, making it an appealing alternative to land-based solar installations. Proponents argue that by covering water surfaces like reservoirs or ponds, floating solar can avoid the need for clearing agricultural or conservation lands, a major concern for traditional land-based solar arrays. However, a recent study brings a dose of caution, revealing some environmental consequences that are less-than-ideal for ecosystems.

The study, published on December 6, 2023, in the prestigious journal Environmental Science & Technology, is the first manipulative field study to investigate the direct environmental effects of floating solar technology. Conducted by researchers from Cornell University, this experiment took place at the Cornell Experimental Pond Facility and examined how solar panels placed on water bodies may affect both the carbon and methane emissions, as well as the health of aquatic ecosystems.

New Evidence on Increased Greenhouse Gas Emissions

The results of the Cornell-led study are striking. Researchers found that floating solar panels placed on small ponds increased greenhouse gas emissions—specifically methane and carbon dioxide—by nearly 27% compared to ponds that were left unaltered by the solar panels. The researchers observed these emissions almost immediately after the solar panels were installed, suggesting that the process of covering the water with solar panels disrupted the delicate balance of gases within these bodies of water.

This spike in greenhouse gas emissions may seem counterintuitive. Solar energy is generally associated with helping mitigate the greenhouse effect by substituting fossil fuels for clean, renewable energy. However, in this case, the new data underscores the ecological trade-offs involved in floating solar technologies—something that was previously not fully understood due to the lack of empirical research.

Dr. Steven Grodsky, an assistant professor of natural resources and the environment at Cornell University, was a lead author of the study. Grodsky explains the significance of the findings: “There have been a flurry of papers about floating solar, but it’s mostly modeling and projections. This is the first manipulative study to produce empirical results. It’s saying, ‘here’s what’s actually happening.’”

The specific increase in methane—a potent greenhouse gas—can largely be attributed to changes in oxygen dynamics beneath the solar panels. As the floating panels covered around 70% of the surface area of the ponds, they created a barrier that blocked sunlight from reaching the water below, altering key environmental processes.

Ecological Disruptions in Aquatic Environments

While the increase in greenhouse gases was an unexpected outcome, the researchers also observed another concerning ecological effect: a significant reduction in dissolved oxygen levels throughout the ponds. Dissolved oxygen (DO) is vital for the survival of many aquatic organisms, including fish, insects, and microbes. With less oxygen in the water, the health of these species can be compromised, disrupting the entire ecosystem and food chain.

Grodsky highlights a broader concern: “If you put floating solar on there, you’re drastically reducing oxygen availability for organisms. You’re messing with ecological processes, like how decomposition takes place, how microbes function, and even how wind moves across the surface of the water. All of these are interconnected.”

Implications for Floating Solar Development

The findings of this study have significant implications for floating solar development, especially in areas like New York state, where renewable energy advocates have begun to explore floating solar as an alternative to land-based solar systems. According to Grodsky, many of the floating solar installations being discussed today are planned for small lakes and ponds. This makes the study particularly relevant for regions where floating solar may soon be considered as a viable energy solution. Notably, Paul Tonko, a U.S. House Representative from New York, sponsored legislation in 2023 that calls for exploring floating solar on U.S. reservoirs.

While the greenhouse gas emissions and ecological disruptions observed in the Cornell study are concerning, it’s important to understand the relative environmental benefits of floating solar. The study’s findings suggest that when compared to traditional energy sources like fossil fuels, floating solar still has a net lower emissions per kilowatt-hour of energy generated. Solar, whether terrestrial or floating, offers significant advantages over coal, gas, or oil-based energy, especially in terms of overall greenhouse gas emissions during its lifecycle (including development, maintenance, and disposal).

The study also shows that floating solar systems are not necessarily a net environmental detriment, but their impacts need careful monitoring and management. For instance, 70% coverage of a pond by solar panels may represent the upper limit of what’s sustainable, as this level appeared to increase both emissions and oxygen depletion. Researchers also suggest potential mitigative measures, such as reducing the surface coverage of the panels or implementing water-agitating devices (known as bubblers) that could help circulate the water and counteract the oxygen depletion.

The implementation of floating solar will always involve balancing trade-offs, according to Grodsky. He argues that it’s essential to be aware of these potential drawbacks to better design and site solar installations so that these adverse effects can be minimized. “Maybe siting differently, designing the panels differently, or changing the percentage of cover” could be some strategies that could allow us to reduce the negative environmental impacts while still benefiting from solar power.

Environmental Considerations for the Energy Transition

This research comes as part of a broader effort within Grodsky’s lab to shift the focus of renewable energy assessments toward a more comprehensive environmental and social perspective. Historically, energy transitions, from wood to fossil fuels and now potentially to renewables, have often been centered around technological advancements and energy production, with environmental costs either ignored or underestimated. In light of challenges such as climate change and environmental injustice, Grodsky emphasizes the importance of integrating ecological considerations into the development of renewable energy technologies early in the process, rather than treating them as secondary concerns after energy production is prioritized.

The research is aimed at helping developers and regulators make informed decisions when it comes to floating solar, with the goal of creating a more balanced energy future. “If you look at the history of energy transitions—from wood to fossil fuels, for example—everything was based on energy production, and the environment wasn’t taken into consideration,” says Grodsky. “The idea here is to nip that in the bud and re-envision the way we approach this energy transition.”

Next Steps: Further Research and Adaptation

As for the future of floating solar, further studies are needed to confirm these findings on a larger scale. While the research at Cornell marks a critical turning point in the evaluation of floating solar technologies, more experiments at different sites with varying climates and bodies of water are needed to understand how universal these results are. Grodsky and his collaborators are continuing to push the boundaries of this knowledge, seeking ways to integrate the best aspects of floating solar technology while minimizing its environmental costs.

By thinking carefully about how floating solar systems are designed, sited, and integrated into ecosystems, researchers hope to pave the way for sustainable, efficient, and responsible energy systems. At the same time, it remains clear that trade-offs will have to be evaluated and balanced as we seek to meet growing global energy demands while safeguarding the health of the planet.

Conclusion: A Cautionary but Promising Path Forward

Floating solar energy presents a promising potential for reducing our carbon footprint and mitigating land use conflicts, but it is not without its environmental trade-offs. The study conducted at Cornell University offers crucial insights into how floating solar panels can impact greenhouse gas emissions and aquatic ecosystems. While these impacts may be tempered by changes in how we approach the technology’s deployment, they highlight the need for careful planning and informed decision-making.

As the world grapples with the challenges of climate change and resource management, technologies like floating solar can help provide a renewable energy solution that works with the natural environment rather than against it. Nevertheless, without vigilant environmental assessment and adaptive strategies, even renewable energy innovations may have unintended consequences.

Incorporating environmental considerations into future energy transitions—like those championed by Grodsky and his team—will be essential to achieving a truly sustainable and equitable energy future. As floating solar gains ground as a powerful clean energy tool, its real-world impacts must be continuously evaluated to ensure that its benefits outweigh its costs in terms of both environmental and social sustainability.

Reference: Nicholas E. Ray et al, Immediate Effect of Floating Solar Energy Deployment on Greenhouse Gas Dynamics in Ponds, Environmental Science & Technology (2024). DOI: 10.1021/acs.est.4c06363

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