Floating solar gaining popularity as unconventional US energy source

For the small, working-class community of Cohoes, New York, climate change and costly energy prices are posing increasing concerns, just as they are for cities and towns across the country.

Now, Cohoes, just 10 miles north of the state’s capital city of Albany, is poised to take an unconventional step toward addressing those concerns by constructing what experts say is the first – or one of the first – municipally-owned and operated floating solar installations in the United States. 

The town plans to install a 3.2-megawatt floating array of solar panels on its 10-acre municipal water reservoir; construction is due to start later this year.

“We have almost no buildable land [within Cohoes],” said Theresa Bourgeois, the town’s director of operations. “But we really wanted to figure out how we could do this within the city.” Floating solar became the obvious solution, she said.

Cohoes projects the floating solar installation will generate enough energy to power all of the municipally-owned buildings and facilities, with excess power available to the town’s school district and housing authority. In all, the project will cost the city about $6 million, and the town is hoping that new provisions in the 2022 Inflation Reduction Act will provide some funding.  

Adaptation growing

China leads the world in floating solar capacity, and other countries in Asia and the Middle East have also been quick to adopt floating solar, according to the National Renewable Energy Laboratory (NREL). 

Floating solar is far less common in the US, but adaptation appears to be on the rise. Before 2016, only two projects had been installed, but the number grew to over 20 by the end of 2020, according to NREL. The largest projects are concentrated in California and Florida. 

A 2019 study by NREL found that if floating solar were installed on just 27% of suitable man-made water bodies, the resulting energy could make up 10% of the nation’s energy production.  

Last year, the California Department of Water Resources announced funding for a $20 million pilot program to install floating solar on farm irrigation canals in Stanislaus County.

Sometimes dubbed “floatovoltaics,” installations of photovoltaic panels can be used on a variety of bodies of water, such as the reservoir in Cohoes. The strategy skirts some of the land-use conflicts associated with traditional, land-based solar, advocates say.

The floating arrays of solar panels are supported by thin, often flexible floatation devices that keep them elevated above the water’s surface and able to move with the waves. A power cable connects the installations to existing energy transmission infrastructure.

It’s possible to build floating solar that lies nearly flat on the water surface, which means it doesn’t catch the eye of passersby. Floating solar design company Ocean Sun, for example, has one such product, which uses a flexible, thin membrane to let solar modules lie flat, said Børge Bjørneklett, the company’s founder. “It’s actually very difficult to see them at a distance,” he said. “They go below the horizon.”

There are obstacles: Situating solar panels on water is generally more costly than covering parking lots with solar panels or mixing them into agricultural production. And little is known about the potential ecological risks that could arise. Also, there is still plenty of open land upon which to build conventional, land-based solar projects. 

Advantages offered

Advocates say that floating solar offers a number of advantages over conventional, land-based solar, especially for regions with less available and affordable land.

It’s not much more difficult to install floating solar versus conventional since floating solar is built mostly with technology that already exists, according to Sika Gadzanku, an energy technology and policy researcher at NREL who has studied floating solar. 

“It’s not a steep learning curve,” she said.

Additionally, the cooling effects of the water beneath the panels can increase the energy efficiency of the installation compared to conventional land-based projects. According to one report by the NREL, the increase can be as much as 3%.

“Essentially, you’re getting more electricity per area of solar,” said Gadzanku. 

The technology could also make sense for water managers looking to keep their town’s reservoirs full and clean. Experts say that floating solar panels block sunlight, lowering the rate of water loss from ponds and slowing the growth of harmful algae.

Building floating solar on hydropower facilities can decrease the cost of electricity transmission, as well. Many floating solar projects in Asia are paired with hydropower dams so that the energy generated from both systems can be transmitted through the same power lines, Gadzanku said. This saves money for local utilities, since they don’t have to build new transmission lines for the floating solar system.

“These projects could be a good renewable energy option for some cities,” said Gadzanku.

In Windsor, California, a wine-country hamlet north of San Francisco, solar panels started floating on the reservoir there in October of 2020, and it is now the third-largest installation in the country, according to NREL. 

Windsor does not own and operate the installation itself, but entered into a 25-year lease and power purchase agreement (PPA) with solar company Ciele & Terre. The 1.78-megawatt floating array generates power for the town’s wastewater treatment plant — one of the biggest consumers of electricity in Windsor. 

The cost of the project was relatively low compared to the energy savings the town now gets from the solar array, said Garrett Broughton, a senior civil engineer for the town. 

“It is a benefit to lock in as much power as you can at a fixed rate,” Broughton said.

Ecological effects

Despite the many benefits, Gadzanku said scientists still don’t know enough about the possible ecological consequences of floating solar, especially if the panels are installed on natural water bodies rather than reservoirs. Since floating solar installations block sunlight and prevent evaporation, they can disrupt the natural growth of organisms in natural water bodies, which could have unknown impacts on underwater ecosystems. 

“If you’re shading a very large fraction of a lake, you can make big changes to that ecosystem,” said Bjørneklett.  Environmental assessments of floating solar projects in natural ecosystems are critical, he said. 

Scientists also aren’t sure how feasible floating solar projects could be at larger scales, since larger water bodies tend to have more powerful waves, tides, and are more susceptible to potentially damaging natural weather events. “Can we design a system that can withstand things like that?” said Gadzanku. “That is something that a lot of different companies in Europe, the US, and Asia are actively looking into.”

(Featured photo: The Town of Windsor’s floating solar array. Photo credit: Noah Berger.)