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Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all ne

Are ground-source heatpumps considered 'geothermal'? Its much less sexy than a giant plant connected to a magma stream, but if we made these routine for all new suburban constructions, alongside passivhaus standards, we could eliminate residential fossil fuel connections for huge sections of the Western world. Like another commenter mentioned, we could even have communal systems for individual streets, drilled beneath roads, to service townhouses and apartment blocks. You can run the ground-source for heating and cooling, alongside a single wall-mounted air conditioner for dehumidification in the summer.

brtkdotse 5y ago
Geothermal heat pumps are very common in the Nordics. It’s a one day operation, they come in, drill a 150M hole and run a brine loop hooked up to a heat pump. Sorts the heating and hot water for a 180 m2 house above the attic circle with less than 7000 kWh per year.
- serpix 5y ago
  that is a ground-source heat pump as the heat energy is mostly from ambient solar. But yes very common and I used to have one in my home before I moved away. It cost practically nothing to keep the house at t-shirt temperature during -25c cold weather snaps.
  - larsalmen 5y ago
    No it's not. The bore-hole is lined with a outer steel pipe until the drill hits bedrock, keeping it very much insulated from the ground. And the upper-most part of the energy-well that's lined is considered inactive, and is not counted in the "150 m deep energy well".
uuddlrlr 5y ago
There's a 52-home community in Alberta that provides ~all of their winter heating by storing heat in the ground throughout the summer: https://www.dlsc.ca/borehole.htm https://www.dlsc.ca/borehole.htm It gets up to nearly 80C, but took a few years of operation to get there. The website covers it really well and I'd recommend checking it out.
- infogulch 5y ago
  Wow that's amazing! Basically a community-sized thermal battery. I find the design curious; they use insulation around the outside, but still bored 144 holes on the inside, I guess the bottom is just left alone as solid rock. They heat it with solar energy, and pull out heat during the winter. I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that experience both, like the midwest US. Perhaps using the pumped water as a stable, biased thermal source for a reversible heat pump.
  - mythrwy 5y ago
    Yes I think that would work. Check out this guy, he grows oranges in Nebraska in thermal heated greenhouses. As I recall he talks about cooling as well. He has tubes around 8 feet under the ground running around the yard. https://www.youtube.com/watch?v=ZD_3_gsgsnk https://www.youtube.com/watch?v=ZD_3_gsgsnk
  - shagie 5y ago
    > I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that experience both, like the midwest US. If there is a difference in the temperature, then the heat can be moved around. However, that doesn't mean you can run the entirety of the heating for the house in the winter off of the heat battery. https://dnr.wisconsin.gov/topic/Wells/Geothermal.html https://dnr.wisconsin.gov/topic/Wells/Geothermal.html > Geothermal works on the principal of using the earth's natural underground temperature and a geothermal heat pump unit to provide heating in the late fall, winter and early spring and cooling in the late spring, summer and early fall. In Wisconsin, the average underground temperatures range from about 52 degrees in the south to 42 degrees in the north. Below about 20 feet in depth, the influence of surface temperature variations begins to dissipate rapidly and becomes the average of all surface temperature values. Note the heating in the late fall and early spring and cooling in late spring to early fall. The Canadian one is stuffing more heat into the battery which gets it above where it is efficient for cooling in the summer. Aside - the wikipedia article for the Canadian one - https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community > On October 5, 2012 the DLSC set a new world record by covering 97% of space heating needs with solar thermal energy. In the 2015-2016 heating season, 100% of space heating needs were met with solar energy. The location is just a bit south of Calgary ( https://www.google.com/maps/place/Drake+Landing,+Okotoks,+AB,+Canada/@50.8523887,-114.1231754,11.15z/data=!4m5!3m4!1s0x537199dd551a1a41:0x8eb9ed0d78e17f0f!8m2!3d50.7268593!4d-113.942308 https://www.google.com/maps/place/Drake+Landing,+Okotoks,+AB... ) For 2020, Calgary had 4835 heating degree days based on 18°C and 72 cooling degree days (2021 has had 174 cooling degree days) https://calgary.weatherstats.ca/charts/cdd-yearly.html https://calgary.weatherstats.ca/charts/cdd-yearly.html and https://calgary.weatherstats.ca/charts/hdd-yearly.html https://calgary.weatherstats.ca/charts/hdd-yearly.html or https://portfoliomanager.energystar.gov/pm/degreeDaysCalculator https://portfoliomanager.energystar.gov/pm/degreeDaysCalcula... Using that last one It's provided in °F too. hdd: 8780 °F and cdd: 117 °F Going back to Wisconsin for the midwest datapoint... https://www.aos.wisc.edu/~sco/clim-history/7cities/madison.html https://www.aos.wisc.edu/~sco/clim-history/7cities/madison.h... - though this data is in °F. The ten year average for heating degree days is 7200 in °F. The ten year average for cooling degree days is 620 in °F. So... Calgary compared to Madison: * 8780 vs 7200 hdd (65 °F) * 117 vs 620 cdd (65 °F) Based on this, and that there is still a lot more hdd than cdd - it would probably be more worthwhile to try to offset the heating costs on the heating degree days than the air conditioning costs on cooling degree days. And just for comparison, Houston, TX is has 1000 hdd 65°F and 3444 cdd 65°F. San Francisco is hdd 2467 °F and 190 °F for cdd. As another note that heating and cooling costs don't scale linearly with heating or cooling degree days.
Freak_NL 5y ago
This is already being done in some countries (e.g., the Netherlands), but it is just a (necessary) part of the puzzle. The existing housing stock needs solutions too, and installing heat pumps in older terrace housing is far from ideal due to noise pollution, cost, lack of space, and a limit to what can be done in terms of insulation. Geothermal plants can be used to provide district heating, which is a much better fit for certain types of houses.
turtlebits 5y ago
Yes, ground source/loop is considered geothermal. The problem is that you need to a dig up a large area of possible natural vegetation to do it.
- rudedogg 5y ago
  You can go vertical instead of horizontal
  - wkearney99 5y ago
    We have two 350' wells for loops at our house in Maryland. Tripled square footage in the new house and energy costs stayed the same. Moved from natural gas for heat, but still have it fir backup (which in a decade has never been needed).
    - slowhand09 5y ago
      You must live in a rural county. There are strict regulations on well depths and aquifers utilized in my area of MD. Two aquifers, one being ~50ft and the other being ~300ft are present, and we have to connect to the deeper of the 2. My neighbor 250ft away has an older house connected to the shallower aquifer. That said, my residential options for energy are rich. I have the Chesapeake Bay 80ft from my current heat pump. So I could theoretically implement a plethora of heat exchange mechanisms taking advantage of that. Wind power is feasible except for the footprint. Yesterdays 35kt gust may have been a bit much tho. Have waves that could power things also. And mostly unobstructed roof which could host solar. Tidal range is not very large, and current is greatly reduced near shore.
- serpix 5y ago
  I had my borehole going straight down about ~150m deep from right next to the side of my house. I moved the lawn right next to the pipes.
  - deleted 5y ago
    [deleted]
generalizations 5y ago
I'd be more interested in residential heat pumps if there were also heat engines that were feasible at that scale. Seems like it needs to scale up by at least an order of magnitude though, before electricity can be generated efficiently.
kragen 5y ago
No, this is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. The difference is not just a matter of sexiness; you can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.
- fulafel 5y ago
  Maybe a factory, many of them use heat in the range that heat pumps are suited for.
  - kragen 5y ago
    Only if they have access to another source of energy to power the heat pump and the other machinery that doesn't run on low-grade heat.
    - fulafel 5y ago
      Sure, factories run on many inputs, you cany do much with just electricity either :)
      - kragen 5y ago
        Energy has a special place: every factory uses it, and you can do a lot with just energy, minerals, labor, and space.
goldenshale 5y ago
Not really. A ground-source heat pump uses the thermally stable ground below a house to heat in the winter and cool in the summer, while a geothermal power plant pumps cool water down a well and then gets hot steam out another connected well to drive turbines.
- fulafel 5y ago
  Geothermal can be used for just heat too, eg district heating. eg https://www.euroheat.org/knowledge-hub/district-energy-iceland/ https://www.euroheat.org/knowledge-hub/district-energy-icela...
dredmorbius 5y ago
Yes, in much the same way that passive or thermal (e.g., hot-water) solar designs are a form of solar power. The principle difference, as others have pointed out, is that when converting heat to mechanical energy, or for electrical generation (mechanical + a generator), efficiency greatly increases as the temperature gradient between the hot and cold ends of the process increases. There's still a lot of utility from lower-grade heat, for space heating (to about 24C/75F), water (about 60C/140F), and cooking (175C/350F). Even a partial boost can assist with other heating methods. But for large-scale electrical generation, high temperatures, well above boiling point, are what are needed. Community thermal energy storage is a thing. That can use either geological formations or specially-constructed insulated structures. Thermal potential may be stored as a hot or cold medium, for heating or cooling.
HPsquared 5y ago
Geothermal power is based on a heat engine: a machine which produces usable energy (e.g. electricity) out of the transfer of heat from a high-temperature heat source to a low-temperature heat sink (a process which would happen naturally, given a transfer process). A ground-source heat pump is a heat pump: a machine which consumes usable energy in order to move heat from a LOW-temperature heat source to a HIGH-temperature heat sink (a process which would not occur naturally without energy input due to the 2nd law of thermodynamics).

brtkdotse 5y ago

Geothermal heat pumps are very common in the Nordics. It’s a one day operation, they come in, drill a 150M hole and run a brine loop hooked up to a heat pump. Sorts the heating and hot water for a 180 m2 house above the attic circle with less than 7000 kWh per year.

serpix 5y ago
that is a ground-source heat pump as the heat energy is mostly from ambient solar. But yes very common and I used to have one in my home before I moved away. It cost practically nothing to keep the house at t-shirt temperature during -25c cold weather snaps.
- larsalmen 5y ago
  No it's not. The bore-hole is lined with a outer steel pipe until the drill hits bedrock, keeping it very much insulated from the ground. And the upper-most part of the energy-well that's lined is considered inactive, and is not counted in the "150 m deep energy well".

uuddlrlr 5y ago

There's a 52-home community in Alberta that provides ~all of their winter heating by storing heat in the ground throughout the summer: https://www.dlsc.ca/borehole.htm https://www.dlsc.ca/borehole.htm It gets up to nearly 80C, but took a few years of operation to get there. The website covers it really well and I'd recommend checking it out.

infogulch 5y ago
Wow that's amazing! Basically a community-sized thermal battery. I find the design curious; they use insulation around the outside, but still bored 144 holes on the inside, I guess the bottom is just left alone as solid rock. They heat it with solar energy, and pull out heat during the winter. I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that experience both, like the midwest US. Perhaps using the pumped water as a stable, biased thermal source for a reversible heat pump.
- mythrwy 5y ago
  Yes I think that would work. Check out this guy, he grows oranges in Nebraska in thermal heated greenhouses. As I recall he talks about cooling as well. He has tubes around 8 feet under the ground running around the yard. https://www.youtube.com/watch?v=ZD_3_gsgsnk https://www.youtube.com/watch?v=ZD_3_gsgsnk
- shagie 5y ago
  > I wonder how well this would work to provide both AC/cooling during the summer and heating during the winter in climates that experience both, like the midwest US. If there is a difference in the temperature, then the heat can be moved around. However, that doesn't mean you can run the entirety of the heating for the house in the winter off of the heat battery. https://dnr.wisconsin.gov/topic/Wells/Geothermal.html https://dnr.wisconsin.gov/topic/Wells/Geothermal.html > Geothermal works on the principal of using the earth's natural underground temperature and a geothermal heat pump unit to provide heating in the late fall, winter and early spring and cooling in the late spring, summer and early fall. In Wisconsin, the average underground temperatures range from about 52 degrees in the south to 42 degrees in the north. Below about 20 feet in depth, the influence of surface temperature variations begins to dissipate rapidly and becomes the average of all surface temperature values. Note the heating in the late fall and early spring and cooling in late spring to early fall. The Canadian one is stuffing more heat into the battery which gets it above where it is efficient for cooling in the summer. Aside - the wikipedia article for the Canadian one - https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community > On October 5, 2012 the DLSC set a new world record by covering 97% of space heating needs with solar thermal energy. In the 2015-2016 heating season, 100% of space heating needs were met with solar energy. The location is just a bit south of Calgary ( https://www.google.com/maps/place/Drake+Landing,+Okotoks,+AB,+Canada/@50.8523887,-114.1231754,11.15z/data=!4m5!3m4!1s0x537199dd551a1a41:0x8eb9ed0d78e17f0f!8m2!3d50.7268593!4d-113.942308 https://www.google.com/maps/place/Drake+Landing,+Okotoks,+AB... ) For 2020, Calgary had 4835 heating degree days based on 18°C and 72 cooling degree days (2021 has had 174 cooling degree days) https://calgary.weatherstats.ca/charts/cdd-yearly.html https://calgary.weatherstats.ca/charts/cdd-yearly.html and https://calgary.weatherstats.ca/charts/hdd-yearly.html https://calgary.weatherstats.ca/charts/hdd-yearly.html or https://portfoliomanager.energystar.gov/pm/degreeDaysCalculator https://portfoliomanager.energystar.gov/pm/degreeDaysCalcula... Using that last one It's provided in °F too. hdd: 8780 °F and cdd: 117 °F Going back to Wisconsin for the midwest datapoint... https://www.aos.wisc.edu/~sco/clim-history/7cities/madison.html https://www.aos.wisc.edu/~sco/clim-history/7cities/madison.h... - though this data is in °F. The ten year average for heating degree days is 7200 in °F. The ten year average for cooling degree days is 620 in °F. So... Calgary compared to Madison: * 8780 vs 7200 hdd (65 °F) * 117 vs 620 cdd (65 °F) Based on this, and that there is still a lot more hdd than cdd - it would probably be more worthwhile to try to offset the heating costs on the heating degree days than the air conditioning costs on cooling degree days. And just for comparison, Houston, TX is has 1000 hdd 65°F and 3444 cdd 65°F. San Francisco is hdd 2467 °F and 190 °F for cdd. As another note that heating and cooling costs don't scale linearly with heating or cooling degree days.

Freak_NL 5y ago

This is already being done in some countries (e.g., the Netherlands), but it is just a (necessary) part of the puzzle. The existing housing stock needs solutions too, and installing heat pumps in older terrace housing is far from ideal due to noise pollution, cost, lack of space, and a limit to what can be done in terms of insulation. Geothermal plants can be used to provide district heating, which is a much better fit for certain types of houses.

turtlebits 5y ago

Yes, ground source/loop is considered geothermal. The problem is that you need to a dig up a large area of possible natural vegetation to do it.

rudedogg 5y ago
You can go vertical instead of horizontal
- wkearney99 5y ago
  We have two 350' wells for loops at our house in Maryland. Tripled square footage in the new house and energy costs stayed the same. Moved from natural gas for heat, but still have it fir backup (which in a decade has never been needed).
  - slowhand09 5y ago
    You must live in a rural county. There are strict regulations on well depths and aquifers utilized in my area of MD. Two aquifers, one being ~50ft and the other being ~300ft are present, and we have to connect to the deeper of the 2. My neighbor 250ft away has an older house connected to the shallower aquifer. That said, my residential options for energy are rich. I have the Chesapeake Bay 80ft from my current heat pump. So I could theoretically implement a plethora of heat exchange mechanisms taking advantage of that. Wind power is feasible except for the footprint. Yesterdays 35kt gust may have been a bit much tho. Have waves that could power things also. And mostly unobstructed roof which could host solar. Tidal range is not very large, and current is greatly reduced near shore.
serpix 5y ago
I had my borehole going straight down about ~150m deep from right next to the side of my house. I moved the lawn right next to the pipes.
- deleted 5y ago
  [deleted]

generalizations 5y ago

I'd be more interested in residential heat pumps if there were also heat engines that were feasible at that scale. Seems like it needs to scale up by at least an order of magnitude though, before electricity can be generated efficiently.

kragen 5y ago

No, this is totally irrelevant to anything in the article, except in the sense that both pertain to thermal energy and the earth. They have nothing else in common. The difference is not just a matter of sexiness; you can't run a factory, a computer, or a car off a ground-source heat pump, because heat pumps consume energy; they don't produce it.

fulafel 5y ago
Maybe a factory, many of them use heat in the range that heat pumps are suited for.
- kragen 5y ago
  Only if they have access to another source of energy to power the heat pump and the other machinery that doesn't run on low-grade heat.
  - fulafel 5y ago
    Sure, factories run on many inputs, you cany do much with just electricity either :)
    - kragen 5y ago
      Energy has a special place: every factory uses it, and you can do a lot with just energy, minerals, labor, and space.

goldenshale 5y ago

Not really. A ground-source heat pump uses the thermally stable ground below a house to heat in the winter and cool in the summer, while a geothermal power plant pumps cool water down a well and then gets hot steam out another connected well to drive turbines.

fulafel 5y ago
Geothermal can be used for just heat too, eg district heating. eg https://www.euroheat.org/knowledge-hub/district-energy-iceland/ https://www.euroheat.org/knowledge-hub/district-energy-icela...

dredmorbius 5y ago

Yes, in much the same way that passive or thermal (e.g., hot-water) solar designs are a form of solar power. The principle difference, as others have pointed out, is that when converting heat to mechanical energy, or for electrical generation (mechanical + a generator), efficiency greatly increases as the temperature gradient between the hot and cold ends of the process increases. There's still a lot of utility from lower-grade heat, for space heating (to about 24C/75F), water (about 60C/140F), and cooking (175C/350F). Even a partial boost can assist with other heating methods. But for large-scale electrical generation, high temperatures, well above boiling point, are what are needed. Community thermal energy storage is a thing. That can use either geological formations or specially-constructed insulated structures. Thermal potential may be stored as a hot or cold medium, for heating or cooling.

HPsquared 5y ago

Geothermal power is based on a heat engine: a machine which produces usable energy (e.g. electricity) out of the transfer of heat from a high-temperature heat source to a low-temperature heat sink (a process which would happen naturally, given a transfer process). A ground-source heat pump is a heat pump: a machine which consumes usable energy in order to move heat from a LOW-temperature heat source to a HIGH-temperature heat sink (a process which would not occur naturally without energy input due to the 2nd law of thermodynamics).