3 ms·

For nordic climates: After running the numbers I was surprised by how little benefit I'd get from geothermal drilling + heat pump for a much larger investment (

by tpmx 5y ago

For nordic climates: After running the numbers I was surprised by how little benefit I'd get from geothermal drilling + heat pump for a much larger investment (like $30k including internal fitting of water-based radiators) compared to a regular outdoor air/air heat pump for $2k. Ongoing costs would be like 5-8% lower. Modern air/air heat pumps are awesome.

Retric 5y ago
Local conditions can dramatically change these numbers. In places where the ground temperature is 20C you use dramatically less energy to heat and cool with a ground source heat pump. Nordic countries have minimal need for cooling and high levels of insulation minimize the need for heating. The worst for heat pumps is simply resistance heating which isn’t that much worse than the a heat pump connected to 5C or less ground temperatures. On top of this 30k is on the high end for ground source heat pumps.
- tpmx 5y ago
  > Nordic countries have minimal need for cooling and high levels of insulation minimize the need for heating. I bought this lovely house built in the 1910s... > On top of this 30k is on the high end for ground source heat pumps. Do note that this estimate included the cost for equipping the house with water-based radioators.
  - Retric 5y ago
    Yea, the water based radiators is a different system than the common approach of having a closed ground loop connected to a heat pump. https://en.wikipedia.org/wiki/Ground_source_heat_pump https://en.wikipedia.org/wiki/Ground_source_heat_pump
- briHass 5y ago
  Define 'much worse'. Even basic heat pumps in traditional air/air split systems can achieve COPs of 3-4 above freezing air temps. The modern mini splits can do that well below freezing. Nowhere has electric so cheap that a 2x or 3x reduction in the amount of electricity used to heat wouldn't result in massive savings.
  - Retric 5y ago
    The issue with thinking in terms of normal ground temperature is two fold. First heat pumps are removing energy in the winter so the ground might normally be 4C but it drops to say 0C. Second your working fluid never reaches soil temperature, so it might end up at -4C next to the pump. Anyway, you only receive benifits when air temperatures are below the temperature of your ground loop. If the outside temperature needs to hit -4C before that happens you’re only benefiting from a smaller percentage of the year. Further that benefit is again constrained by the delta between resistance heating and what your ground source is providing the heat pump. Generally it takes a combination of lower cooling costs in the summer and lower warming costs in the winter to make ground source heat pumps worth it, so being limited to a few months in the winter vs a 20+k installation cost is prohibitive.
- aaron695 5y ago
  > On top of this 30k is on the high end for ground source heat pumps. When I priced it, this was normal. Perhaps $20,000 would be a a good price - https://www.youtube.com/watch?v=IMO9jvwlHFg&t=634s https://www.youtube.com/watch?v=IMO9jvwlHFg&t=634s Also I assume we are talking Geoexchange (For lack of a better word) not Geothermal. Temperature differentials not radioactive decay Digging holes and installing infrastructure just costs too much money. Air heat pumps simple, things like being noisy is also getting solved which is awesome.
kragen 5y ago
Your comment is entirely unrelated to the article, which is about using the very hot rock several kilometers underground to drive turbines to generate electricity.

by tpmx 5y ago

Retric 5y ago

Local conditions can dramatically change these numbers. In places where the ground temperature is 20C you use dramatically less energy to heat and cool with a ground source heat pump. Nordic countries have minimal need for cooling and high levels of insulation minimize the need for heating. The worst for heat pumps is simply resistance heating which isn’t that much worse than the a heat pump connected to 5C or less ground temperatures. On top of this 30k is on the high end for ground source heat pumps.

tpmx 5y ago
> Nordic countries have minimal need for cooling and high levels of insulation minimize the need for heating. I bought this lovely house built in the 1910s... > On top of this 30k is on the high end for ground source heat pumps. Do note that this estimate included the cost for equipping the house with water-based radioators.
- Retric 5y ago
  Yea, the water based radiators is a different system than the common approach of having a closed ground loop connected to a heat pump. https://en.wikipedia.org/wiki/Ground_source_heat_pump https://en.wikipedia.org/wiki/Ground_source_heat_pump
briHass 5y ago
Define 'much worse'. Even basic heat pumps in traditional air/air split systems can achieve COPs of 3-4 above freezing air temps. The modern mini splits can do that well below freezing. Nowhere has electric so cheap that a 2x or 3x reduction in the amount of electricity used to heat wouldn't result in massive savings.
- Retric 5y ago
  The issue with thinking in terms of normal ground temperature is two fold. First heat pumps are removing energy in the winter so the ground might normally be 4C but it drops to say 0C. Second your working fluid never reaches soil temperature, so it might end up at -4C next to the pump. Anyway, you only receive benifits when air temperatures are below the temperature of your ground loop. If the outside temperature needs to hit -4C before that happens you’re only benefiting from a smaller percentage of the year. Further that benefit is again constrained by the delta between resistance heating and what your ground source is providing the heat pump. Generally it takes a combination of lower cooling costs in the summer and lower warming costs in the winter to make ground source heat pumps worth it, so being limited to a few months in the winter vs a 20+k installation cost is prohibitive.
aaron695 5y ago
> On top of this 30k is on the high end for ground source heat pumps. When I priced it, this was normal. Perhaps $20,000 would be a a good price - https://www.youtube.com/watch?v=IMO9jvwlHFg&t=634s https://www.youtube.com/watch?v=IMO9jvwlHFg&t=634s Also I assume we are talking Geoexchange (For lack of a better word) not Geothermal. Temperature differentials not radioactive decay Digging holes and installing infrastructure just costs too much money. Air heat pumps simple, things like being noisy is also getting solved which is awesome.

kragen 5y ago

Your comment is entirely unrelated to the article, which is about using the very hot rock several kilometers underground to drive turbines to generate electricity.