[mb7733]

> We can extract a lot more energy from fossil fuels in large scale plants

This isn't true at all for natural gas. Burning it for heat in the home is much more efficient than burning it in a plant, converting it to electricity, transferring that electricity, then turning that electricity into heat.

[maxwwwt]

The theoretical efficiency maximum for burning gas in a home is 100%. Most systems won't hit that because they need to vent waste gases, which carry some heat away.

Heat pumps are significantly more efficient than 100%. They can get to 500% efficiency. So no, it's definitely not more efficient to burn gas in a home. (To say nothing of the safety of running gas lines to every house.)

[jjk166]

Heat pumps are best for small thermal gradients. If you want your room to be a nice 70F while it's 50F outside, a heat pump is a very efficient way of heating your room. If you want a blow torch that's hundreds of degrees above ambient, a heat pump is terribly inefficient. The exact cutoff where gas heating becomes more efficient is variable, but it's typically a temperature differential between 40 and 60F.

[mb7733]

Completely separate conversation. I was responding to the statement "We can extract a lot more energy from fossil fuels in large scale plants".

[floatrock]

You might be missing the point of heat pumps, and your statement was really about end-heat in homes.

You said

> Burning it for heat in the home is much more efficient than burning it in a plant, converting it to electricity, transferring that electricity, then turning that electricity into heat.

Burning it for heat in the home may be something like: 99% transport efficiency (gas distribution systems lose maybe 1%) * 80% combustion efficiency (a lot of heat energy still goes out your chimney as exhaust). Call it 79%. If you spent more for a high-efficiency burner with extra heat-recovery stages, you could get into the 90's.

Compare to: burning it in a plant (power plants can run efficient combined-cycle infrastructure, which is about 60% efficient turning it into electricity), transferring that electricity (plant-to-home transmission & distribution losses are 8-15%, so call it 85%), then turning that electricity into heat (and here is where heat pumps shine... heat pumps don't burn electricity, they use it to move heat, so they can have efficiencies above 100%).

So compare that 79%-90% "burn for heat in the home" efficiency to 60% * 85% * 300-500% = 150-255% efficiency for "burn it in a plant, convert to electricity, transfer that electricity, then turn that electricity into heat".

[mb7733]

I completely understand your point. I know what a heat pump is and how it works. They are great. I am not anti heat pump. I am pro heat pump.

It's just not the point I was actually responding to. The OP was under the impression that you would be "extracting a lot more energy" from the gas in a plant vs the home.

Yes, converting gas to electricity allows you to use a heat pump, which in many cases uses much _less_ energy than a furnace to heat a home. (As long as it's not too cold.)

But that's just not what I was talking about. I was talking about the claim of extracting _more_ energy from the gas. Good day!

[gabrielhidasy]

Depends, if you are turning that electricity into heat using a heat-pump you might win on most situations (maybe lose if the weather is really cold outside, unless you add geothermal loops, but then its a lot more expensive to make)

[fhn]

No it wouldn't depend. Electricity generation and electricity transfer has losses. Gas transfer has loss only if there is a leak.

[andruby]

Heat pumps have a COP value of around 4 to 5 (10 to 15C outdoor) and 3 (0C outdoor). The seasonal COP (or SCOP) measures the efficiency over a whole season, and that typically sits around 3 to 4. That means that for 1kWh of electricity a heat pump delivers 3 to 4kWh of heat to the house.

Burning gas to heat a home means "1kWh" of gas, delivers ~1kWh of heat.

Modern gas power plants are about 55 to 60% efficient, so "1kWh" of gas becomes ~0.57kWh of electricity, which after transport losses (-6%) arrives at the home as 0.52kWh, which gets turned into 1.5 to 2.0kWh of heat.

=> It's almost two times as efficient to turn gas into electricity and use heat pumps in the home

[Tuna-Fish]

The ceiling is not 100% efficient, when you have a heat pump.

Also, the US residential gas infrastructure leaks ~1% of the gas it moves. That sounds like nothing, until you account for how unburnt ch4 is ~80 times worse than co2 on a timescale of 20 years.

[idontwantthis]

That is false. Heat pumps are more efficient than burning gas in a home even when the electricity came from burning gas.

[mb7733]

It does not follow that "We can extract a lot more energy from fossil fuels in large scale plants"

[thelastgallon]

In addition the sibling comments (COP of heat pumps is 500%), air pollution in homes is worse than air pollution outside. If you don't have natural gas and burning fuel, it helps a lot. Not only is electricity cheaper and cleaner, but also healthier.

[mb7733]

Not what I replied to

[mbreese]

But isn't it more advantageous to have the gas -> electricity conversion in a plant from an emissions point of view? You still have losses in the system when moving natural gas around from the source to individual homes too (leaks). In theory you don't, but in practice you do.