Massachusetts is getting district geothermal system

There are two types of geothermal energy systems: the type that taps into hot spots like near volcanoes in Iceland, and the type (sometimes referred to as ground-source) that benefits from the steady temperature of the earth. If you have a basement, you’ll be familiar with the latter. It’s always cooler in the summer and warmer in the winter than the air temperature because it’s moderated by the earth around it. This temperature, around 55 degrees F, is the happy place for heat pumps, maximizing their effectiveness.

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When Dale and I built a house in Sedona, we put in a ground source heat pump system that worked well. Framingham is building a community scale system that will serve 31 residences and five commercial buildings. Doing it at this scale should reduce the costs associated with drilling and put responsibility for maintaining the underground system on the utility, not individual home owners.

At the start of June, Eversource Energy commissioned the United States’ first networked geothermal neighborhood operated by a utility, in Framingham, Massachusetts. Pipes run down boreholes 600 to 700 feet deep, where the temperature of the rock is consistently 55 degrees Fahrenheit. A mixture of water and propylene glycol (a food additive that works here as an antifreeze) pumps through the piping, absorbing that geothermal energy, then flows to 31 residential and five commercial buildings, where fully electric heat pumps use the liquid to either heat or cool a space. If deployed across the country, these geothermal systems could go a long way in helping decarbonize buildings, which are responsible for about a third of total greenhouse gas emissions in the U.S.

https://grist.org/climate-energy/decarbonizing-buildings-geothermal-network-solutions/

You might recall that some refrigerants are potent greenhouse gases. This system at least uses propylene glycol, which you might even find in your ice cream. If made from plants instead of fossil fuels, it can have a much lower greenhouse gas potential.