Just a 10-minute drive from Albany, at the confluence of the Mohawk and Hudson rivers, the future of energy is taking shape at the City of Cohoes’s water filtration plant. There, on the plant’s 10-acre pond, filled with water pumped up from the Mohawk, solar panels on plastic floats bob on the surface.
Cohoes mayor, Bill Keeler, and Sharon Butler, the city’s commissioner of Building and Planning, watch as workers in high-visibility life vests stoop among the rows of floating solar panels like high-tech farm workers. Only, instead of harvesting crops, these workers are completing electrical hookups that will soon send up to 3.2 megawatts (MW) of DC power to the shore, where inverters will convert it to AC power for the electric grid.
According to Keeler, the city stands to realize a savings of $500,000 to $600,000 in its annual municipal energy costs—pretty much the entire bill—once the system gets hooked up. “So instead of it being a budget concern, it gives me optimism that we won’t have to raise taxes again next year,” he says. And the savings are likely to grow. “We all know energy costs keep going up,” Butler says. That is, for non-renewable sources, unlike the fixed costs of solar power.
The Cohoes facility is the newest in a growing number of floating solar arrays, or floatovoltaics, that aim to capture the benefits of solar power while leaving behind some of the drawbacks.
Floating on Sunshine
Floatovoltaics are nothing new. They’ve been in operation in the US since a Far Niente Winery installed a system on its irrigation pond in Oakville, California, in 2008. But they’re more plentiful abroad—for example, in Japan, where the first prototype went online in 2007; China, home of the world’s largest installation; and India, where a 600 MW facility isn’t much smaller.
But the Cohoes installation is the first in New York State, and the first in the country owned and operated by a municipality, according to Keeler.
The newest (and at 8.9 MW, the largest in the country) of two systems in New Jersey, both owned and operated by NRJ Clean Energy Ventures, went online at the Canoe Brook water treatment plant in Short Hills in 2023.
Butler estimates that the final cost of the Cohoes system will come in around $7.2 million. The city received a $3 million federal grant for the project, secured by Congressman Paul Tonko, whom Keeler says has been a strong supporter. The New York State Energy Research and Development Authority (NYSERDA) will provide $1 million on project completion through its NY-Sun program. Additional money comes from the US Inflation Reduction Act, leaving about $1 million as the city’s responsibility. That means, given the anticipated energy savings, the city should recoup its investment in the array in about two years of operation.
Although not specifically named in New York’s plan to reduce carbon emissions from all economic activity in the state by 85% from 1990 levels by 2050, floatovoltaics could play a significant role. Legislation recently introduced by state senator Pete Harckham calls for NYSERDA to provide financial incentives and education to boost floating solar development.
Siting solar arrays on water eases competition for land needed by terrestrial arrays. “They’re not taking up valuable farm space,” as Keeler puts it. The cooling effect of the water keeps the panels closer to their optimal operating range, boosting efficiency. The array in Cohoes also gets an efficiency boost from an additional feature. “The panels are more efficient because they also get reflection from the water,” says Andy Wittman, project manager for DLC Electric, the project’s Troy-based contractor. “It absorbs sunlight in either direction. It’s bifacial.” Wittman expects the array to last at least 30 years—comparable to terrestrial systems.
By shading the water, floating arrays also cut down on algae growth, something Patrick Fuss, acting utility director for the City of Healdsburg, in northern California, can attest to from experience. Healdsburg’s floating solar array went online on its water treatment plant holding pond in 2021. Fuss says the difference in the quality of water leaving the pond to irrigate nearby vineyards is visible.
“The water was this pea green soup-ish kind of color, and now it’s very clear,” Fuss says. The algae growth caused problems for the vineyards. “The vineyards use drip irrigation here, which has a very small orifice at each one of the lines, and it clogs up their emitters,” Fuss explains. “But since we’ve had the floating solar out there, the algae’s been curtailed, and we’ve not had those complaints again.”
Keeler looks forward to reducing algae growth at the Cohoes filtration plant as well. “Where the panels are covering, you won’t get the algae,” he says. “So there’ll be a lot of savings in the chemicals that we use to treat that.” He also expects the shade to save water. “We lose a lot of water to evaporation, as you would imagine, over such a big surface area,” he says.
Floatovoltaics do present some challenges, including, at least in the case of the Healdsburg facility, from an unexpected source.
Keeping Cleantech Clean
Fuss says the city of Healdsburg didn’t anticipate geese liking the town’s floating panels a little too much. “Geese being geese, they just let loose wherever they are,” Fuss says. Goose droppings on the panels reduce power output, so now, the array’s owner and operator, White Pine Renewables, regularly sends out a cleaning crew. Keeler and Butler don’t anticipate a goose problem at the Cohoes site.
Less of an issue for day-to-day operations is the potential for floatvoltaics to increase greenhouse gas emissions from the water they float on, even as they potentially offset emissions by replacing non-renewable sources of power. A study published last year by researchers at Cornell University found that ponds covered with solar panels release about 27% more greenhouse gases than open ponds due to changes in the water’s chemistry and temperature. Still, the study’s authors conclude that the emissions are lower than for terrestrial solar farms.
One of those authors, Liz Kalies, lead renewable energy scientist for The Nature Conservancy’s North America region, also contributed to a study on the impacts of floatovoltaics on biodiversity and recreational water use. “People have a really special relationship with water, and many communities have strong identities linked with boating, fishing and other water activities,” she says. “The most important finding for communities is that even in the most cautious approach…there are still many opportunities for floatovoltaics in the Northeast.”
Kalies and her coauthors conclude that even taking potentially problematic bodies of water out of the running, the Northeast (including New York, New Jersey, Connecticut, Massachusetts, and Pennsylvania) could increase its solar power generation by 5% with floatovoltaics, including in places like the Cohoes filtration plant. Five percent might not sound like a lot, but Kalies calls it significant. “It could be the equivalent of taking nearly 40 million passenger cars off the road for a year while avoiding development on tens of thousands of acres of land.”
Powering Cohoes’s Future
After completion in September, the Cohoes array’s 5,880 panels will cover 75% of the reservoir’s surface, with open water on all sides for access by maintenance crews via boat. Seventy-four tethers will connect the floating array to anchor points on the shore rather than in the water to avoid possible contamination with underwater drilling. Weights will keep the tethers below the surface and out of the way of the maintenance boats.
Connection to the electric grid, via National Grid, will have to wait until next year due to the power company’s scheduling constraints, but may come as soon as February, according to Butler. The electricity won’t be exclusively for the city’s use, but it will allow Cohoes to offset the cost of lighting the city’s streets, music hall, town offices, and more.
“It’s great for the environment and there’s a savings for the municipality,” Keeler says. “So what’s not to like about it?”
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Solar energy equals: everything made in China. $$$ electrician to disconnect. Huge refuse / disposal cost. And manpower to throw out. Water runoff that is toxic. Should I keep going.
Only if you stop spreading falsehoods…
What a great project. We need one in Kingston. We also need more articles written that are as well crafted and reseached as this one.
I think it’s an ingenious idea — hopefully with more benefit than cost, given the observation re “27% more greenhouse gases than open ponds.”
And, maybe a dumb Q here: is there any aquatic life in that sort of pond?
Thanks for any insights–
These are artificial ponds, so what life there is finds its way in after they’re created. In Cohoes’s case, it’s algae. In Healdsburg’s case, it’s also carp, which the operators figure were dropped there by birds somehow (pelicans?).