MikeB, you introduced this in relation to a heat pump:MikeB wrote: ↑Thu Jul 18, 2024 5:08 amThat, as far as I know, is a pre-requisite for any heat-engine, but otherwise I'm not sure what the relevance is?
And to expand that slightly - for any engine/motor (whether it be electric; a waterwheel; or steam) the most basic pre-requisite is a transfer of energy from high potential to a lower potential.
Reproducing from above:
If I carry a can of gasoline there are "two inputs of energy" in what seems to me the same sense.MikeB wrote: ↑Tue Jul 16, 2024 9:04 amI think this was answered several posts earlier, but the point is that a heat-pump has TWO inputs of energy, one electrical, the other ambient air or ground (depending which kind it is.)
That is why it is called a pump, and not a heater, though it should really be called an "External Refrigerator" or something similar, as it works exactly the same as a domestic fridge - leccy in, heat moved from cold place to warmer place.
I carry an empty can to the gas station, fill it with gas and take it home then pour it into the gas tank of whatever engine. Car, lawn mower, tractor.
The energy expended by my muscles to lift and transport the FUEL is negligible, You appear to be arguing above that the energy used to transport heat by a heat pump doesn't really count much at all.
So, which is it?
On the one hand the apparent "overunity" of a COP >1 is dismissed as irrelevant. Heat pumps and heat engines are fundamentally different. The 2nd Law and Carnot don't apply, but if we want to use that to our advantage to transport heat to a heat engine all of a sudden you can only get as much energy out of your FUEL as you used to transport it.
That is something I've tried to point out many times.
Heat pumps and heat engines are fundamentally VERY different in principle and result.
One is not the other "running in reverse".
A heat pump merely transports heat/energy from one location where it is useless to us, to another location, where it becomes useful.
A heat ENGINE on the other hand actually consumes the "FUEL" or transforms the energy which moves into its sphere of influence.
Only in the Carnot/caloric theory does a heat engine operate by the mere transfer of energy from one location to another.
We are not lifting our gasoline and pouring it over a water wheel to let it down again.