Comment by MengerSponge
21 hours ago
Resistive heating is a tremendously inefficient way to generate heat. Sometimes it's worth it if you get something useful in exchange (such as full spectrum light in the winter). But it's not all upsides.
Heat pumps are magic. They're something like 300% efficient. Each watt generates 3 watts of useful heat.
I share your enthusiasm about heat pumps, but I wonder what the efficiency of using waste heat is. Couldn't it be competitive with heat pumps? As it's a waste product, isn't it reasonable to also expect it to be more than 100% efficient?
As a rule of thumb (obviously it varies) you spend about 1% pumping water round a heat network. So your CoP is around 99 if you consider heat truly free. It's actually higher as pump energy largely is converted to friction/heat.
You can’t extract energy from heat by itself. Only from a heat delta.
Think of heat like flowing water or charge. Only an altitude or voltage delta creates the flow needed to harvest energy.
You get no useful energy from heat you are already trying to shed because you have no delta to work with. (The entire problem exists because there is no surrounding environment with high heat capacity and lower heat.)
What is waste heat depends on your usecase. Using waste heat from industrial processes for district heating is done in some places.
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Much more than 100% since the only energy you need to put in is for pumping the hot water around.
Its not inefficient if you were creating the heat anyway, its a completely free byproduct.
Yeah. This. Obviously if the objective is just to generate heat only buy a heat pump and not a B200!