5 ms·

Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always mor

by jcynix 5y ago

Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Heat exchange in the house happens through floor heating. So during a hit summer, the reverse capability just pumps the cold water through our floors (controlled for the dew point) and the warm floor water into the ground. That, combined with controlled ventilation over a physical heat exchanger, keeps the warmth out. Or, during cool seasons, the warmth in. Our heat pump uses about 1 Kwh electricity (from ecological resources like water or wind only) to generatev3 to 4 Kwh of heating. Without producing carbon dioxide. Airflow based heat pumps are less efficient, and more noisy outside, of course.

mprev 5y ago
What sort of problems did you encounter drilling two 60m deep holes? How wide are they?
- brtkdotse 5y ago
  Usually 100-150mm wide. You don't do it yourself, you get a company with a drilling rig to come out and do it. Costs around 5k€.
- jcynix 5y ago
  We did have no problems as the ground below consists mostly of clay for at least 100 meters. Two times at 60m was a political limit 10 years ago, because at 100 meters "suddenly" mining rules applied. The tubes are about 100 mm in U-form, drilling mostly is offered in combination with the heat pump. And costs where payed of after about 7 years. Costs and problems depend on the ground's structure. When I talked with the guys of the drilling team, they told me that problems occur if they work in hill regions with cavernous spots in the ground. That's because the tubes need firm contact to the ground to transfer heat. Edit: here's an image of the drilling machine in operation: http://www.cynix.net/2008/img_1757.jpg http://www.cynix.net/2008/img_1757.jpg and the tubes are those black ones on the rolls in the front.
elric 5y ago
> Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Good point. The source and destination of heat can be air, water, or "ground source". But it's still all just the same concept as A/C units. Pump heat to one place, using less energy than what it would take to heat it using resistance heating. There is nothing special about ground source heat pumps, except that they're a pain to install in densely populated areas. All types of heat pumps, unfortunately, often leak. Depending on the type of refrigerant they use, this can be a serious climate concern as well.
- jcynix 5y ago
  There's no refrigerant here. Our heat pump uses plain water mixed with an anti-freezing agent. Just like the cooler in a car does. And there are control displays where you control all operating parameters. As for the "pump heat from here to there" ... while we are cooling we are warming the ground below. And as at our place, the ground's consistency keeps the warmth rather local, we reuse it later when we warm our water during the night. We do live in a densely populated area and about every fifth hoiuse built here during the last 10 years uses a ground-based heat pump. As for electricity use: each house has two hours of "blockage" where the pump is not allowed to run, so that the power lines aren't stressed. That's no problem at all, because all houses are highly insulated and thus buffer rather good.
  - bluGill 5y ago
    There is refrigerant there. It is contained inside the system, and only your water mix leaves, but there is still refrigerant inside and it can leak.
    - jcynix 5y ago
      That's correct. I was comparing our system to existing systems which directly use a refrigerant sent into the ground loop. Our heat pump itself is a closed system just as a refrigerator, and works indirectly via the water cycle used outside.
brtkdotse 5y ago
> Airflow based heat pumps are less efficient, and more noisy outside, of course. This is only true when the ambient temperature dips below the geothermal temperature which depending on your location should make you prefer one over the other.
- jcynix 5y ago
  Germany. Where temperatures dip for some months below the geothermal temperature. Efficiency of air based pumps drops markedly when temperatures reach below 0 degrees Celsius. And last but not least: ground / water carries much more energy per volume unit than air does. So air based heat pumps would make more sense in Europe's south and less sense farther north.
  - brtkdotse 5y ago
    Modern water/air heat pumps have surprsingingly high efficiency down to -20C. We're running a 10 year old model that has no trouble heating our house down to -12, after which a direct electric helper element kicks in.
sidewndr46 5y ago
Is English a second language for you? I ask not because I am trying to insult, but what you are describing is just called geothermal heat in North America. It can also work in reverse if the air temperature is higher than the ground temperature. Also, you have your units wrong. Electrical demand is measured in just kilowatts (kw). Actual usage is in kilowatts-hours (kwh) which is just an unusual way of saying joules.
- scotty79 5y ago
  Units are fine. He just said he gets energy as heat in the amount 4 times higher than amount of electrical energy he uses to get it. It's fine to talk about it in terms of energy as it would be to talk about it in terms of power. And I'd argue that kWh is exactly the usual way of saying 3600000 joules. Also name "geothermal heat" for ground heat pumps might be a local US marketing term. In international English geothermal means rather what Iceland is mostly doing. Pumping water into very hot rocks deep below to extract heat. And it doesn't work in reverse because it would be additional work to pump heat into very hot rocks instead of dumping it into the air or into the cool ground 2 meters below the surface.
  - sidewndr46 5y ago
    I don't know anything about Iceland but I am using the definition from energy.gov https://www.energy.gov/energysaver/heat-and-cool/heat-pump-systems/geothermal-heat-pumps https://www.energy.gov/energysaver/heat-and-cool/heat-pump-s... Geothermal works with either vertical holes in the ground or a big loop spread out horizontally. Neither one is very deep nor does it involve hot rocks.
    - scotty79 5y ago
      Ah, geothermal heat pumps is perfectly accurate. Geothermal heat on the other hand is a wider term https://en.m.wikipedia.org/wiki/Geothermal_heating https://en.m.wikipedia.org/wiki/Geothermal_heating of which geothermal heat pumps (ground source heat pumps) https://en.m.wikipedia.org/wiki/Ground_source_heat_pump https://en.m.wikipedia.org/wiki/Ground_source_heat_pump are just a subset.

by jcynix 5y ago

mprev 5y ago

What sort of problems did you encounter drilling two 60m deep holes? How wide are they?

brtkdotse 5y ago
Usually 100-150mm wide. You don't do it yourself, you get a company with a drilling rig to come out and do it. Costs around 5k€.
jcynix 5y ago
We did have no problems as the ground below consists mostly of clay for at least 100 meters. Two times at 60m was a political limit 10 years ago, because at 100 meters "suddenly" mining rules applied. The tubes are about 100 mm in U-form, drilling mostly is offered in combination with the heat pump. And costs where payed of after about 7 years. Costs and problems depend on the ground's structure. When I talked with the guys of the drilling team, they told me that problems occur if they work in hill regions with cavernous spots in the ground. That's because the tubes need firm contact to the ground to transfer heat. Edit: here's an image of the drilling machine in operation: http://www.cynix.net/2008/img_1757.jpg http://www.cynix.net/2008/img_1757.jpg and the tubes are those black ones on the rolls in the front.

elric 5y ago

> Good heat pumps aren't of the air conditioner type. Our heat pump uses two 60m deep drilled holes. Thus heat exchange happens in the ground, which is always more or less 10 degrees Celsuis. Good point. The source and destination of heat can be air, water, or "ground source". But it's still all just the same concept as A/C units. Pump heat to one place, using less energy than what it would take to heat it using resistance heating. There is nothing special about ground source heat pumps, except that they're a pain to install in densely populated areas. All types of heat pumps, unfortunately, often leak. Depending on the type of refrigerant they use, this can be a serious climate concern as well.

jcynix 5y ago
There's no refrigerant here. Our heat pump uses plain water mixed with an anti-freezing agent. Just like the cooler in a car does. And there are control displays where you control all operating parameters. As for the "pump heat from here to there" ... while we are cooling we are warming the ground below. And as at our place, the ground's consistency keeps the warmth rather local, we reuse it later when we warm our water during the night. We do live in a densely populated area and about every fifth hoiuse built here during the last 10 years uses a ground-based heat pump. As for electricity use: each house has two hours of "blockage" where the pump is not allowed to run, so that the power lines aren't stressed. That's no problem at all, because all houses are highly insulated and thus buffer rather good.
- bluGill 5y ago
  There is refrigerant there. It is contained inside the system, and only your water mix leaves, but there is still refrigerant inside and it can leak.
  - jcynix 5y ago
    That's correct. I was comparing our system to existing systems which directly use a refrigerant sent into the ground loop. Our heat pump itself is a closed system just as a refrigerator, and works indirectly via the water cycle used outside.

brtkdotse 5y ago

> Airflow based heat pumps are less efficient, and more noisy outside, of course. This is only true when the ambient temperature dips below the geothermal temperature which depending on your location should make you prefer one over the other.

jcynix 5y ago
Germany. Where temperatures dip for some months below the geothermal temperature. Efficiency of air based pumps drops markedly when temperatures reach below 0 degrees Celsius. And last but not least: ground / water carries much more energy per volume unit than air does. So air based heat pumps would make more sense in Europe's south and less sense farther north.
- brtkdotse 5y ago
  Modern water/air heat pumps have surprsingingly high efficiency down to -20C. We're running a 10 year old model that has no trouble heating our house down to -12, after which a direct electric helper element kicks in.

sidewndr46 5y ago

Is English a second language for you? I ask not because I am trying to insult, but what you are describing is just called geothermal heat in North America. It can also work in reverse if the air temperature is higher than the ground temperature. Also, you have your units wrong. Electrical demand is measured in just kilowatts (kw). Actual usage is in kilowatts-hours (kwh) which is just an unusual way of saying joules.

scotty79 5y ago
Units are fine. He just said he gets energy as heat in the amount 4 times higher than amount of electrical energy he uses to get it. It's fine to talk about it in terms of energy as it would be to talk about it in terms of power. And I'd argue that kWh is exactly the usual way of saying 3600000 joules. Also name "geothermal heat" for ground heat pumps might be a local US marketing term. In international English geothermal means rather what Iceland is mostly doing. Pumping water into very hot rocks deep below to extract heat. And it doesn't work in reverse because it would be additional work to pump heat into very hot rocks instead of dumping it into the air or into the cool ground 2 meters below the surface.
- sidewndr46 5y ago
  I don't know anything about Iceland but I am using the definition from energy.gov https://www.energy.gov/energysaver/heat-and-cool/heat-pump-systems/geothermal-heat-pumps https://www.energy.gov/energysaver/heat-and-cool/heat-pump-s... Geothermal works with either vertical holes in the ground or a big loop spread out horizontally. Neither one is very deep nor does it involve hot rocks.
  - scotty79 5y ago
    Ah, geothermal heat pumps is perfectly accurate. Geothermal heat on the other hand is a wider term https://en.m.wikipedia.org/wiki/Geothermal_heating https://en.m.wikipedia.org/wiki/Geothermal_heating of which geothermal heat pumps (ground source heat pumps) https://en.m.wikipedia.org/wiki/Ground_source_heat_pump https://en.m.wikipedia.org/wiki/Ground_source_heat_pump are just a subset.