The Boston Green Ribbon Commission delegation visits the seawater heat pump system in Esbjerg, Denmark, in 2025.
Credit: Green Ribbon Commission

The technology, intended to capture thermal energy from the Charles and Mystic Rivers, Boston Harbor, the Fort Point Channel and bedrock beneath, would be a closed system that circulates heat through sealed infrastructure without drawing water from waterways.  

“It's one that's been demonstrated and proven on campuses and for suburban areas, but we haven't investigated this technology deeply for dense urban areas like the city of Boston,” says Peter McPhee, senior director for building decarbonization at the Clean Rnrtgy Center. "We haven't looked into the feasibility yet of utilizing water resources like Boston Harbor as a source of energy that could heat or cool these buildings.”

The hope is that “anchor” institutions—such as hospitals, universities and large businesses—will connect to the network and have access to lower cost and cleaner energy. The system isn’t carbon neutral, but it is far cleaner than the alternative.

“There is an amount of electricity that's used for both the [buildings’] heat pumps and for pumping [water] in, but when we look at the math on that, what it says is that even if you do this today, even though a portion of that electricity is coming from fossil fuels, it's still far cleaner to do that than to be combusting fossil fuels,” McPhee says,

 As for the impact of a thermal energy system on a river system like the Charles River, he says it could actually have a mitigating effect on the temperature increases caused by global warming.

“By extracting heat from these water bodies, we can control it in a way that returns the temperatures back to pre-global warming temperature profiles," he says, "which can be very beneficial to the ecology and really mitigate some of the challenges we're having with warmer temperatures.”  

Installation of piping for Framingham Geothermal Energy Network in 2023.
Credit: Eversource and HEET

The project is timely given the volatility of the global market for fossil fuels.

“We're all very aware of the volatility and prices of fossil fuels and the supply of fossil fuels, with a lot of what's happening in the world today,” says McPhee. “A lot of businesses and consumers are cognizant of that as well, and they're looking to get on to more stable and lower cost energy sources that's good for the business and good for your household.”  

The commission will gather building data from the area’s largest energy users to shape its analysis of thermal energy use at scale, and will also work with government entities, regulated utilities and district energy providers to address underground infrastructure and regulatory barriers.

The commission seeks a qualified engineering firm or technical consultant to lead the project, with proposals due April 29 and the RFP located at  greenribboncommission.org/2026/04/cleanthermalrfp.