3 ms·

Geothermal should be an obvious choice for new-build homes. Put a ground-source heat pump source in the ground, and build your home on top of it.

cyberax 2y ago
This works well only in a few cases. If you live in an area like Pennsylvania or New York, then you're far better off with an air-source heat pump. It's cheaper to install, and the average air temperatures are warm enough for the air source to work well. If you live in a place like Minnesota, then the ground-source pump needs a water table. Or you'll just be freezing the water in the ground. And you'll likely still be better off with an air-source pump.
- maxerickson 2y ago
  The ground loop just needs to be deep enough to be in a zone with relatively stable temperatures. Apparently 6 to 8 feet in Minnesota: https://www.minnesotageothermalheatpumpassociation.com/geothermal/earth-loop-options/ https://www.minnesotageothermalheatpumpassociation.com/geoth... (note, the 6 to 8 feet is for a closed loop, horizontal system)
  - cyberax 2y ago
    The heat pump works by pumping the heat out of the ground. And the soil is a pretty good insulator, so you'll eventually just freeze the water in the soil around the pipes. It looks like this: one day in winter, the temperature of the coolant in the loop outlet falls below 0C. And after that, it starts dropping down by about 1C a day, until the pump becomes a resistive heater. If you sized your loop correctly, it hopefully happens towards the end of the heating season.
    - boxed 2y ago
      If your ground heat system also provides cooling that's no longer a problem. I have that for my house. It's pretty great. You're basically time-shifting temperatures across the year. Cool temperatures get shifter to summer and warm to winter. The hole itself won't freeze, because you're not significantly pulling or pushing energy down it.
      - cyberax 2y ago
        Even without running the AC, you generally will likely get enough heat flux from the surface and (hopefully) from the water table to thaw the ice during the summer for horizontal loops. I don't have a personal experience with vertical loops.
epistasis 2y ago
This is very different from the sort of geothermal being discussed for power generation. Residential geothermal for home heating and cooling could make a ton of sense, but more likely based on the scale of a residential natural gas network. Drilling a hole per home is super expensive. Replacing gas pipes with moderate thermal pipes would be about the same cost as gas infrastructure but allow the massive efficiency gains of larger scale. Heat pumps operating on pumped water through these sorts of pipes doesn't need very high or low delivered temperatures to be effective, as long as it's somewhat above the -20C of the extremes of winter. Thermal storage quantity scales roughly with volume (x^3) and storage costs roughly scale with surface area (x^2). Though I'm not sure if storage plays much into the gas -> thermal plans that have been explored.
- spockz 2y ago
  We have that in the Netherlands in plenty of cities called “stadsverwarming”. It is hot water pumped around in a closed loop and residences take heat out of it with heat pump. The source is the cooling off industries, power plants, or dedicated heaters. They currently are efficient but still expensive because of a law that the pricing has to be similar to heating with would have been.
  - epistasis 2y ago
    Thanks for the extra context! Could you explain the law on pricing a bit more? What was the motivation, and what is the usual alternative heating source?
    - brrt 2y ago
      Natural gas, from the Slochteren gas field, was the cheapest way to heat a home for the past 60 years. It's probably not so anymore, considering the Slochteren field is mostly shut down. The city heating network operator is a monopoly, that is why the price is capped. Even though city heating networks utilize 'waste heat', the capital cost of the network is significant. The price cap and the capital costs (especially now with higher interest rates) led to many proposed projects being cancelled in recent years.
rad_gruchalski 2y ago
The problem, as I understand it, is that one has to drill and hit the pocket where the geothermal power comes from. Now, here in Eifel, every drilling requires a permit (€€€), every drilling costs about €20k, you may have to drill more than once to hit the pocket. And Eifel sits on an old mega volcano.

cyberax 2y ago

This works well only in a few cases. If you live in an area like Pennsylvania or New York, then you're far better off with an air-source heat pump. It's cheaper to install, and the average air temperatures are warm enough for the air source to work well. If you live in a place like Minnesota, then the ground-source pump needs a water table. Or you'll just be freezing the water in the ground. And you'll likely still be better off with an air-source pump.

maxerickson 2y ago
The ground loop just needs to be deep enough to be in a zone with relatively stable temperatures. Apparently 6 to 8 feet in Minnesota: https://www.minnesotageothermalheatpumpassociation.com/geothermal/earth-loop-options/ https://www.minnesotageothermalheatpumpassociation.com/geoth... (note, the 6 to 8 feet is for a closed loop, horizontal system)
- cyberax 2y ago
  The heat pump works by pumping the heat out of the ground. And the soil is a pretty good insulator, so you'll eventually just freeze the water in the soil around the pipes. It looks like this: one day in winter, the temperature of the coolant in the loop outlet falls below 0C. And after that, it starts dropping down by about 1C a day, until the pump becomes a resistive heater. If you sized your loop correctly, it hopefully happens towards the end of the heating season.
  - boxed 2y ago
    If your ground heat system also provides cooling that's no longer a problem. I have that for my house. It's pretty great. You're basically time-shifting temperatures across the year. Cool temperatures get shifter to summer and warm to winter. The hole itself won't freeze, because you're not significantly pulling or pushing energy down it.
    - cyberax 2y ago
      Even without running the AC, you generally will likely get enough heat flux from the surface and (hopefully) from the water table to thaw the ice during the summer for horizontal loops. I don't have a personal experience with vertical loops.

epistasis 2y ago

This is very different from the sort of geothermal being discussed for power generation. Residential geothermal for home heating and cooling could make a ton of sense, but more likely based on the scale of a residential natural gas network. Drilling a hole per home is super expensive. Replacing gas pipes with moderate thermal pipes would be about the same cost as gas infrastructure but allow the massive efficiency gains of larger scale. Heat pumps operating on pumped water through these sorts of pipes doesn't need very high or low delivered temperatures to be effective, as long as it's somewhat above the -20C of the extremes of winter. Thermal storage quantity scales roughly with volume (x^3) and storage costs roughly scale with surface area (x^2). Though I'm not sure if storage plays much into the gas -> thermal plans that have been explored.

spockz 2y ago
We have that in the Netherlands in plenty of cities called “stadsverwarming”. It is hot water pumped around in a closed loop and residences take heat out of it with heat pump. The source is the cooling off industries, power plants, or dedicated heaters. They currently are efficient but still expensive because of a law that the pricing has to be similar to heating with would have been.
- epistasis 2y ago
  Thanks for the extra context! Could you explain the law on pricing a bit more? What was the motivation, and what is the usual alternative heating source?
  - brrt 2y ago
    Natural gas, from the Slochteren gas field, was the cheapest way to heat a home for the past 60 years. It's probably not so anymore, considering the Slochteren field is mostly shut down. The city heating network operator is a monopoly, that is why the price is capped. Even though city heating networks utilize 'waste heat', the capital cost of the network is significant. The price cap and the capital costs (especially now with higher interest rates) led to many proposed projects being cancelled in recent years.

rad_gruchalski 2y ago

The problem, as I understand it, is that one has to drill and hit the pocket where the geothermal power comes from. Now, here in Eifel, every drilling requires a permit (€€€), every drilling costs about €20k, you may have to drill more than once to hit the pocket. And Eifel sits on an old mega volcano.