Cohoes’ Floating Solar Array—A Municipal Model of Renewable Energy: Part One

A Q&A with Joseph Seman-Graves, Former Cohoes City Planner
By Alexander Morse

In September 2023, the Rockefeller Institute coordinated with New York Congressman Paul Tonko to host the Locally Sourced: Capital Region Climate Policy conference in which policymakers, researchers, and state, federal, and local government practitioners convened to discuss the latest research and initiatives aimed to improve environmental sustainability and reduce the carbon footprint at the municipal level.

Joseph Seman-Graves, former Cohoes city planner, presented at the conference on the city’s planning and development for floating solar utilizing its existing reservoir—a first-in-the-state approach to renewable electricity generation. In this Q&A, we follow up with Seman-Graves on the project to learn more about its electricity generation capacity and environmental advantages, as well as Cohoes’ efforts to leverage public-private partnerships and savings from other environmental projects to secure financing for implementation.

Part One of the Q&A introduces the City of Cohoes, including its demographics, infrastructure, and geographic qualities, as well as its energy needs. The conversation also introduces floating solar as a model for renewable electricity generation and what other environmental advantages floating solar presents the city as a tool to help reduce greenhouse gas emissions and improve environmental sustainability.

Part Two focuses on the collaborations and partnerships with research institutes, federal and state governments, and private industries that helped municipal leaders gain expertise in an emerging technology and begin project planning. The conversation also explores how savings from Cohoes’ previously achieved environmental sustainability projects were leveraged to unlock financing for implementation.

Part One

Alexander Morse: For those unfamiliar with Cohoes, can you tell us a little bit about the city, including its demographics, its infrastructure, how many municipal buildings there are, and other important characteristics?

Joseph Seman-Graves: Cohoes is in Albany County, in upstate New York, at the confluence of the Mohawk and Hudson rivers. In terms of infrastructure, we have a lot of old buildings, historic city-owned buildings, including our city hall, music hall, and libraries. We also have three firehouses, a water treatment plant, and a couple of ancillary buildings for storage. Altogether, 13 buildings are municipally owned. Traditionally, the city was an old mill town and we had a lot of industrial activity on the waterways. There is now an environmental justice designation for the city. These characteristics are not unique to Cohoes, a lot of upstate cities are just like us, but we are kind of exemplary in the form of the build and some of the demographics that you would see around here.

The city’s area is four square miles, and we have about 18,900 residents, so fairly dense for its size. Our population saw a decline in the mid-1900s but we’re back on the uptick now. Demographics have changed over time, but traditionally, a middle, lower-middle working-class city, and capacity-constrained city in terms of just financial ability to kind of maneuver with different projects, initiatives, and services. The city is 54 percent LMI (low-to-moderate income) majority population. These are the demographics of communities that are currently being included in the renewable energy transition or trying to be included at the federal and state levels.

AM: The City of Cohoes is implementing an innovative approach to trying to achieve some of its energy goals and efficiencies, and one of those approaches is floating solar. Tell us a little bit about what floating solar is and what are some of its environmental advantages.

JSG: On a basic level, it’s like any solar array that you would see in a field, except it’s on a dock. That’s the very basic gist of it. As I mentioned, we have a very dense community and not a lot of opportunities for available land. So, one of the advantages is that there’s an asset that we have in the middle of our city—our reservoir that’s currently fenced in and provides 10 acres of open water. That’s an available space that is already city-owned and therefore wouldn’t need to come off the tax roll. Otherwise, we’d have to look at some other properties and acquire them for this kind of use. The reservoir is something that we just have in front of us, and it’s not being utilized to its fullest degree. And, if you’re working at a utility company, you look at this just like you would look at any other interconnection in their system.

Other advantages are not limited to energy generation. There’s going to be a decrease in algae growth on the water surface and that will save the city money. Currently, we’re putting in about $130,000 a year to treat algae. And that’s just algae—not to mention what we’re treating on the back end to get those chemicals out. While the cost to implement floating solar is a little bit higher—since the engineers, technology, and manufacturing are not currently located in New York State—we’re paying a little bit extra right now. However, we are going to see a little bit more savings because panel performance is going to be increased due to the cooling effect of the water.

So, there are a number of advantages: not using developable space or undeveloped space, the increased performance of the panels, as well as the reduction of money and chemicals going into the water to treat such things as algae blooms. We don’t have this as much in the Northeast yet, but out west, they’re putting panels on reservoirs or putting panels on similar facilities. It’s not the only approach, but it’s definitely another tool in our toolbox to consider when we’re looking at the energy transition.

AM: Do you have an estimate of the reduction in greenhouse gas emissions as a result?

JSG: Yes, roughly, we’re looking at about 1,300 metric tons of carbon dioxide here.

AM: That’s quite a significant number. It’s interesting that there are so many advantages floating solar presents for electric generation and environmental sustainability. Are there any other places that can implement floating solar arrays?

JSG: There are a lot of municipalities that can benefit from floating solar. If you look at the 2018 NREL (National Renewable Energy Lab) report that we are kind of basing this project off of—the report looked at water sources in the US and how this technology could be used on these water sources, and what kind of energy production that could have—the report identified 24,000 water bodies, and reservoirs similar to Cohoes’ that, if used, could generate 10 percent of the nation’s energy.

When you get into the actual engineering, permitting, and designing of a project like this, there are a lot of things that can change when you get to the local level. But through this project, we have spoken with a lot of developers, municipalities, and decision-makers across the country, trying to learn about the technology. It’s been interesting seeing the different kinds of applications they have. But in New York State alone, there are potentially 492 of these locations. So definitely something that could be not only replicated in the state, but across the country.

The report identified 24,000 water bodies and reservoirs similar to Cohoes’s that, if used, could generate 10 percent of the nation’s energy… In New York State alone, there are potentially 492 of these locations.

AM: Let’s use Cohoes as a case study and talk a little bit about what the current electricity demands are. What is the current demand? And how much does that cost the city?

JSG: In 2020, we were using approximately 3.5 million kilowatt hours a year (kWh/year) as a city. And that was between our streetlights and our buildings. Now, one of the other things we did was convert our streetlights to LEDs so that dropped our energy usage down to about 2.8 million kWh/year today. The solar project is going to generate about 4.15 million kWh/year in its first year.

So ultimately, we’re going to see about 60 to 65 percent of the array going towards our city needs: buildings, lights, municipalities, and roughly 35 to 40 percent of the array leftover for additional uses, whether it’s sharing with the school district, or banking the credits for future years where productivity might be low. But ultimately, we’re going to use about 60 percent of the array to cover 100 percent of our municipal electric needs.

We’re going to use about 60 percent of the array to cover 100 percent of our municipal electric needs.

AM: That’s fantastic. The net surplus alone is such a valuable resource to have.

JSG: Yes, and if I can touch on that for a second… We originally went to New Jersey where the Sayreville, New Jersey, floating solar project was already built in 2020. And they were working on a second project, the Canoe Brooke Project, which is currently the largest floating array in the United States at 8.9 megawatts (MW). To put it in comparison, a small array in other areas of the world is like 50 MW, which is more than 15 times the size of Cohoes’. But one thing that we learned is that the Canoe Brook Project was capped at 25 percent coverage of their water body. And that was strictly because the first one, Sayreville, was 25 percent coverage—so, that’s just the new norm there.

Considering any environmental concerns that might be raised, we said, “Let’s get as much coverage as we possibly can so the next array that comes in doesn’t have to be arbitrarily limited in size based on our first permanent one in the state.” So, we chose to do as much as we could, covering about 67 percent of our reservoir and generating almost 40 percent more energy than we needed. We did that intentionally, knowing there are definitely end uses for that 40 percent that we can easily find, but we didn’t want to arbitrarily set a limit.

Read part II of the Q&A.

If you want to keep learning more about Cohoes’ floating solar initiative or about other municipal solutions to environmental sustainability, watch the Rockefeller Institute’s Locally Sourced: Capital Region Climate Policy conference.


Alex Morse was associate director of public policy and government strategy at the Rockefeller Institute of Government and is now regulatory affairs specialist at New York Independent System Operator.