Why put solar panels on the surface of water?

Story at a glance

• Floating photovoltaics work much like traditional solar installations with the exception of their location: They float on bodies of water.

• The concept has been catching on over the years, particularly in Asia.

• A 2018 study from the National Renewable Energy Laboratory (NREL) estimated that installing floating solar installations on the more than 24,000 man-made reservoirs in the U.S. could produce around 10 percent of the nation’s annual electricity production.

Floatovoltaics — or solar panel installations built to float on bodies of water — are emerging as a useful tool in the world’s quest to ramp up renewable energy sources and cut greenhouse gas emissions.

Just last month, the Army rolled out a floating solar farm atop the Big Muddy Lake at Fort Bragg in North Carolina as part of the military branch’s climate strategy to increase the use of clean energy. The 1.1 megawatt system, the largest of its kind in the Southeastern U.S., will help supply power to the nation’s largest domestic military base and provide power during electric service outages. The installation is the first deployed by the Department of Defense and marks growing interest in the U.S. for the technology.

Meanwhile in New Jersey, construction is underway to build the largest floating solar array in the U.S. The 8.9 megawatt structure made up of more than 16,000 solar panels will sit on a reservoir at the Canoe Brook Water Treatment Plant, which serves customers in parts of Essex, Morris, Passaic, Somerset and Union counties and is expected to generate 95 percent of the facility’s annual power needs through a power purchase agreement. The system is expected to be completed in the fall of 2022.

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But the U.S. has largely lagged behind many other regions of the world in deploying floating solar technology. Asia is currently the largest market for floating solar; specifically Southeast Asia, where installing traditional solar farms is pricey due to the high cost of land, yet hydropower is abundant, and thus, many reservoirs ideal for floating solar arrays are available for use. Currently, the 320 megawatt Dezhou Dingzhuang Floating Solar Farm in China is the largest floating PV project to come online to date.

According to researchers, floatovoltaics may very well have the potential to solve many issues associated with traditional domestic solar energy installations. A 2018 study from the National Renewable Energy Laboratory (NREL) estimated that installing floating solar installations on the more than 24,000 man-made reservoirs in the U.S. could produce around 10 percent of the nation’s annual electricity production.

How do floating solar panels work?

Floating photovoltaics work much like traditional solar installations with the exception of their location. Solar panels are secured to buoyant structures like plastic pontoons to keep them afloat on the surface of a body of water. The installations are typically located in man-made bodies of water, such as reservoirs from wastewater treatment plants, drinking water reservoirs or hydropower plants.

What are the advantages of floating solar?

There are several unique advantages to installing a floating solar farm versus traditional solar projects. One obvious advantage is floating systems avoid taking up valuable and expensive land near population centers that could otherwise be used for housing, infrastructure or agriculture. Traditional solar farms are land intensive and tend to take up more space on a per-watt basis than fossil fuels.

There is research suggesting that solar panels may operate more efficiently when buoyed on the surface of water, although researchers note more work needs to be done to conclude whether that’s the case.

“What we see is that when you put the panels on the water you’re able to lower the temperature of the panels and some of the cooling effects essentially increase the efficiency of a solar panel,” Sika Gadzanku, an expert of floating solar technologies with the NREL, said in an interview.

“So you’re able to produce more solar power compared to a land-based system. So that’s one of the big advantages when you’re just thinking about power.”

Gadzanku said panels are also able to be packed tighter for floating solar compared to traditional systems due to the difference in tilting to draw power from the sun. There’s also no risk of shading because the system sits on a reservoir. The shade the floating systems produce may also help reduce evaporation from water bodies, which could be particularly advantageous for areas susceptible to droughts.

There are also hybrid-related benefits associated with installing floating solar in coordination with hydropower plants.

“If you install it in a place with existing transmission you don’t need to build transmission. So you’re saving money there,” Gadzanku said.

“During the dry seasons, there are concerns if there’s not as much rain. Now, if you had floating solar paired with hydro, you can reduce your reliance on hydro during the wet season and save that water for use during the dry season. So there’s a lot of potential benefits there.”

Disadvantages and unknowns

One drawback is that floating solar technology currently costs more to develop than land-based solar and are generally more practical for large-scale application. The racking system also needs to be high corrosion resistant and have a long lifespan.

Researchers have also stressed more research needs to be done on the potential environmental impacts of the technology.

“A lot of the installations started with artificial reservoirs because they don’t have as many questions about potential impacts on the water body,” Gadzanku said.

“But once you go into natural water bodies, then you need to think about ecosystem impacts…With floating solar, you’re installing on so many different water body types in so many different climatic regions, so research in one country can tell you something, but it won’t tell you everything. That makes things a bit tricky.”

It’s also unclear how plastics and metals from the floating mechanisms will impact the quality of the water, if it impacts the growth of algae or the broader ecosystem.

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