A lot of the green energy transition is already well underway. PV solar and wind are already cheaper than gas, and electric vehicles are at near cost parity with ICE and much more fun to drive. Major countries like Germany and the UK already get more than half of their electricity from non-fossil sources. The emissions from advanced economies actually dropped by 4.5% from 2022 to 2023, and are down to 1990 levels, according to the IEA: CO2 Emissions in 2023. They burn less coal than they did in 1900.
The next biggest emission wedge to convert is heating and cooling, and there the answer is clear – heat pumps. These exchange heat between the inside of a building and an exterior heat reservoir, and can heat or cool. There are two main types: air-source and geothermal. The air-source heat pumps are basically reversible air conditioners. They can make hot outside air cold or vice-versa. They then move it into the house through a fluid and then to air ducts. They need big outside fans and so can be noisy, and don’t work that well in cold winters, when they have to raise the outside temperature by 30 or 40C.
It’s better to use a heat reservoir with a more constant temperature, like the ground. This is geothermal. Water pipes are either run deep into the ground in a U-shaped well, or are buried under a backyard. The ground is at a constant year-round temperature of 13C in Massachusetts, and so works well for heating and cooling all year round. The big issue is getting that big run of pipe in somewhere, since that’s expensive.
Here’s where networked geothermal comes in:
Instead of having a pipe for each building, have a system for a whole street managed by a utility. Each place maintains its own heat pump, just as they now do for a gas furnace, but a central authority handles the wells and the piping. The system expands smoothly as more buildings are added. This has lots of advantages over individual wells or air-sources:
- The cost of the wells is amortized over lots of customers. A single well costs tens of thousands.
- The pumps use a reservoir close to the building temperature, and so get very high seasonal coefficients of performance (SCOP). That’s the ratio of heat energy out to electrical energy in over a whole year. An air-source pump might get 3.0, but geothermals get more than 5. This means less electricity cost for everyone, and less strain on the grid. ISO New England says that electricity demand in its region has dropped by about 20% over the last 20 years as more efficient lighting is used, manufacturing improves and more residential solar panels are put in, but they expect it to rise by 20% as more heat pumps and EVs are used. Better SCOPs will help.
- The plumbing is no longer a one-off project, but is installed and maintained regularly by experts, which also lowers costs and speeds conversion.
- The system can be sized for the average over a number of buildings, rather than having to meet the peak of one. Yet another cost savings.
- The system can be handled by the gas utility, and so can convert over smoothly as gas heat is retired. This is a big political advantage, since there is no longer a big incumbent resisting the new scheme. It benefits union labor too!
The scheme is being promoted by a Massachusetts group, the Home Energy Efficiency Team, heet.org. They maintain a Gas to Geo Wiki with info about every aspect of the plans. The first gas-utility-backed trial started in 2022 in Framingham MA with this route:
The loop is about a mile long and is buried 5 feet deep. It uses 8″ plastic pipes with thick walls. It will cover 36 buildings with 24 residential (apartments and houses) and 12 commercial. The in-house installation of the heat pumps is due to finish this summer of 2024. The main boreholes are in a parking lot in the middle.
The people participating will all get huge breaks on their heating bills. There are already big rebates available: $15K from MA and $8700 US. Since the average MA geothermal install is $44k, this can cut the cost by more half.
So this sounds like a win for everyone! The utility and unions get future work, the customers get clean and quiet heating and cooling that doesn’t smell from leaks or occasionally explode, and the planet gets less emissions. I hope this comes to our neighborhood soon!
A Niche in the Library of Babel 
This very interesting, I hope more cities try it. I wonder what your opinion of this article would be: https://solar.lowtechmagazine.com/2019/02/heat-your-house-with-a-mechanical-windmill/ ..Could networked heating/cooling work with this too?
Generating heat directly with a windmill is an interesting idea for remote locations! It’s easy to have a lot of storage with an insulated water tank. It can also be mechanically coupled to a compressor to run a heat pump for greater heat output and for AC. Still, electricity is so useful for everything else that you would want to do that you’re bound to need a generator on the windmill anyway.
Remote locations, right! And how about for backup in the event of a power outage? Could direct heat generation be useful in such situations, for getting and storing heat even when the wind is not strong or consistent? And could networked district heating systems help for that scenario too? Could a networked geothermal and networked wind-heat even perhaps share infrastructure, for e.g. if the network began with wind but then, when expanded to encompass a larger area, adds in geothermal..?
The networked geothermal described above is a bit different from district heating schemes in that each building has its own heat pump. Instead of supplying heat centrally, and having to have insulated pipes, the big loop is just supplying water at a constant medium temperature. If you did have a central source of heat like a windmill, or maybe actual geothermal from deep underground, then you would have to worry about heat losses as the working fluid was moved around the district. The district schemes that I’ve seen move heat around in steam pipes because that’s a really efficient way to move heat, but it does need bigger pipes and special channels. In the networked geothermal, you actually want the fluid to be at the ground temperature, in order to have something for the pump to work against.
So I think this mechanically-pumped-via-windmill works great for local uses. Each building would need its own windmill in that scheme. That’s not good for urban areas, but rural ones should do fine.
Fascinating, thank you