6 ms·

Losses mean something because they demonstrate the efficiency of a particular conversion, and demonstrate the overall size of the inefficiency compared to other

Losses mean something because they demonstrate the efficiency of a particular conversion, and demonstrate the overall size of the inefficiency compared to other problems in the system. Two quick examples: (1) LED light vs incandecent where incandescent's rejected energy is waste heat (2) Natural gas used to heat a house versus natural gas used to generate electricity to run an electric home heater. The direct use rejects far less heat. This is information that can lead to policy. If you see a lot of waste in a particular path that could be substituted with a different path, policy could be used to encourage the more efficient path. For example, due to abundant hydroelectric energy, the Northwest US used to use a lot of electric heating. Once hydro no longer met demand, the government had a commercial campaign to educate consumers about how they could save money by switching to gas.

ZeroGravitas 9y ago
The home heating thing is interesting, since burning gas for that is roughly 100% efficient. Burning gas for electricity maxes out in the best possible case at 60%, and then there's some tranmission loss (though I suppose gas leaks from pipes need to be counted as well then). But, electric heat pumps don't generate heat but, as the name suggests, "pump" it from one place to another, so they can be more than 100% efficient, generating something like 2-3x the input energy for air source, or up to 5 for ground source pumps. Which puts electrity ahead again (especially as some of that electricty can come from low carbon sources rather than gas).
- Declanomous 9y ago
  Heat pumps only work in mild climates though. From what I understand, you can't heat your home with a heat pump in a place like Wisconsin, where the temperature is below 0F for a fairly substantial part of the winter. I hadn't even heard of a heat-pump until recently, which makes sense, since they seem to mostly be concentrated in warm, dry areas. Edit: According to Wikipedia, I'm specifically thinking of Air-source heat-pumps, which have a terrible coefficient of performance below 17 degrees Fahrenheit. Geothermal is better, though I believe you still have problems with saturation in cold climates.
  - s0rce 9y ago
    If you don't have natural gas or want to burn wood, basically your only choice is electric resistive heating (COP = 1) or an air source heat pump (COP > 1, above 10-15F) (other options like ground/water source heat pumps are possible but expensive/need specific conditions), the heat pump option will be more efficient, even in a cold place. When it gets cold enough that the heat pump isn't performing you simply turn on the auxiliary resistive heaters instead, there will at least be some days in the shoulder season where the heatpump is beneficial from an efficiency standpoint. If it makes economic sense is another matter. I think if you are going to get central AC or a minisplit its not that much more expensive to get a heatpump. If you have natural gas it makes sense, economically, to use that to heat most places in the USA.
  - atqtion 9y ago
    > you can't heat your home with a heat pump in a place like Wisconsin... Geothermal is better, though I believe you still have problems with saturation in cold climates Geothermal heat pumps can definitely work in the portions of the upper midwest. I know some people in both MLK and Madison that have heat pumps. As far as I understand it's hit and miss, though. Depends on the particular piece of property you're living on. And you may need an additional heat source for occasional use (e.g. the super cold winter a couple years back I know one of those folks were super glad they still had gas heating in addition to the heat pump). > I hadn't even heard of a heat-pump until recently, which makes sense, since they seem to mostly be concentrated in warm, dry areas. Ironically I'm the other way around. Didn't hear about heat pumps until moving north. Probably because heat pumps don't make as much financial sense in warmer climates where you're not blowing $100+/mo on heat?
    - toomuchtodo 9y ago
      My air conditioner in Tampa has a reverser valve to run as a heat pump when it's cold out; it'll run down to 0F using only the air source condenser unit.
      - Declanomous 9y ago
        My understanding is the limit to the heating potential of a heat pump system is the evaporator freezing over, which is why they are more popular in areas with low humidity. I think at a certain point the heat pumps spend so much time in defrost mode with the auxiliary heater running that they aren't economical.
- cjensen 9y ago
  A minor nit: Burning gas for heating is not 100% efficient, unless you really want to die of carbon monoxide poisoning. Combustion gasses are exhausted to the atmosphere. Heat is transferred via a heat exchanger into the recirculated internal air of the house. [1] https://en.wikipedia.org/wiki/Central_heating https://en.wikipedia.org/wiki/Central_heating

ZeroGravitas 9y ago

The home heating thing is interesting, since burning gas for that is roughly 100% efficient. Burning gas for electricity maxes out in the best possible case at 60%, and then there's some tranmission loss (though I suppose gas leaks from pipes need to be counted as well then). But, electric heat pumps don't generate heat but, as the name suggests, "pump" it from one place to another, so they can be more than 100% efficient, generating something like 2-3x the input energy for air source, or up to 5 for ground source pumps. Which puts electrity ahead again (especially as some of that electricty can come from low carbon sources rather than gas).

Declanomous 9y ago
Heat pumps only work in mild climates though. From what I understand, you can't heat your home with a heat pump in a place like Wisconsin, where the temperature is below 0F for a fairly substantial part of the winter. I hadn't even heard of a heat-pump until recently, which makes sense, since they seem to mostly be concentrated in warm, dry areas. Edit: According to Wikipedia, I'm specifically thinking of Air-source heat-pumps, which have a terrible coefficient of performance below 17 degrees Fahrenheit. Geothermal is better, though I believe you still have problems with saturation in cold climates.
- s0rce 9y ago
  If you don't have natural gas or want to burn wood, basically your only choice is electric resistive heating (COP = 1) or an air source heat pump (COP > 1, above 10-15F) (other options like ground/water source heat pumps are possible but expensive/need specific conditions), the heat pump option will be more efficient, even in a cold place. When it gets cold enough that the heat pump isn't performing you simply turn on the auxiliary resistive heaters instead, there will at least be some days in the shoulder season where the heatpump is beneficial from an efficiency standpoint. If it makes economic sense is another matter. I think if you are going to get central AC or a minisplit its not that much more expensive to get a heatpump. If you have natural gas it makes sense, economically, to use that to heat most places in the USA.
- atqtion 9y ago
  > you can't heat your home with a heat pump in a place like Wisconsin... Geothermal is better, though I believe you still have problems with saturation in cold climates Geothermal heat pumps can definitely work in the portions of the upper midwest. I know some people in both MLK and Madison that have heat pumps. As far as I understand it's hit and miss, though. Depends on the particular piece of property you're living on. And you may need an additional heat source for occasional use (e.g. the super cold winter a couple years back I know one of those folks were super glad they still had gas heating in addition to the heat pump). > I hadn't even heard of a heat-pump until recently, which makes sense, since they seem to mostly be concentrated in warm, dry areas. Ironically I'm the other way around. Didn't hear about heat pumps until moving north. Probably because heat pumps don't make as much financial sense in warmer climates where you're not blowing $100+/mo on heat?
  - toomuchtodo 9y ago
    My air conditioner in Tampa has a reverser valve to run as a heat pump when it's cold out; it'll run down to 0F using only the air source condenser unit.
    - Declanomous 9y ago
      My understanding is the limit to the heating potential of a heat pump system is the evaporator freezing over, which is why they are more popular in areas with low humidity. I think at a certain point the heat pumps spend so much time in defrost mode with the auxiliary heater running that they aren't economical.
cjensen 9y ago
A minor nit: Burning gas for heating is not 100% efficient, unless you really want to die of carbon monoxide poisoning. Combustion gasses are exhausted to the atmosphere. Heat is transferred via a heat exchanger into the recirculated internal air of the house. [1] https://en.wikipedia.org/wiki/Central_heating https://en.wikipedia.org/wiki/Central_heating