Concentration of CO2 in the Atmosphere

Solar to Float in Cohoes, New York Reservoir

Cohoes water reservoir. (Google Earth via NREL)

George Harvey

Cohoes, New York, is a working-class city with a population of about 17,000. Its municipal electricity bills run to $660,000 per year. People have looked at how to use clean energy to provide power to the city from a local source, but the problem of how to do it did not appear to have easy solutions. There is almost no money available, and there was very little land that could be used for the project.

When Theresa Bourgeois, Cohoes’ director of operations, and City Planner Joe Seman-Graves started doing some serious research on how to find a solution, Seman-Graves had an inspiration. It was to develop a floating solar array on the city’s water reservoir.

With that thought, they focused on learning as much as they could about floating solar systems. They discovered that the technology had been proven, it was already in use in various places around the world. There were, however, comparatively few such systems in the United States, and none of them was owned by a municipal government.

Things started to brighten up when their research came to reports that had been done by the National Renewable Energy Laboratory (NREL) on the potentials of floating solar systems. In 2018, NREL had done a report on how they could be used in this country. This report is “Floating Photovoltaic Systems: Assessing the Technical Potential of Photovoltaic Systems on Man-Made Water Bodies in the Continental United States” (FPS), and it is available at

One thing Bourgeois and Seman-Graves found in the report was that the reservoir at Cohoes had already been identified as having potential for a floating solar array. And while they saw that no municipal floating solar arrays had yet been built, there are almost 25,000 man-made bodies of water on which floating solar systems could be built. They could identify 492 such reservoirs in the state of New York.

A solar array is floated on a dam, river, reservoir, or lake to reduce evaporation and keep the solar PV panels cool for optimal performance. (Adobe stock/534786576/Tsvetan)

That is exciting news – much more than a casual reader might realize, at first glance. Since a floating array at Cohoes would be the first of its type to be built in the United States, it could be a prototype system, a system that can prove the concept for this country. Also, given the great number of systems that can be built, it can prove very important, because there are quite literally thousands of systems that might be built by people who have studied it.

With this, they began to look at more reasons to build floating solar arrays on reservoirs. With some help from John Erickson, director of research operations at Rensselaer Polytechnic Institute’s Institute for Data Exploration and Applications, they were able to put together visuals comparing potential locations for floating solar arrays with locations of low- to moderate-income communities. They found the correspondence compelling. It shows that communities with reservoirs that have potential for floating solar systems often stood to benefit quite a lot from them.

With their research in hand, they started visiting state and federal agencies, along with others possible sources, looking for help with financing a floating solar array. The quality of their research was sufficient that Cohoes was able to get significant government funding, including $3 million in federal funding, along with a $750,000 grant from National Grid. This covers well over half of the cost of the system, which is expected to be $5.9 million.

The array is scheduled to be installed, according to the city, and it should be working by the spring of 2025, at the latest. When that happens, 60% of its electricity will be used to reduce the city’s costs for electricity. The other 40% can be used for other purposes, such as helping some of the residents whose needs are greatest.

There are other benefits to this system, however, because it points the way toward broader future development. The estimate from NREL is that about 10% of the nation’s electricity can be provided by similar systems. This would be electricity, provided by the sun, without any need to develop land that can be used for other things. In addition, there is the benefit that floating solar systems reduce evaporation of the water they are on. They will help decarbonize the country, and they will help reduce air pollution.

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