this post was submitted on 31 Jul 2023
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Did you... did you just claim over 100% efficiency? Physics has an issue with this. Also, I have something to tell you, a heat pump is just a reversible Air Conditioner.
Definitely better than a electric heater or a gas furnace, not some sort of miracle product.
Yes, they are typically calculated as having above 100% efficiency as they use the energy to move and concentrate heat instead of producing it like other heating systems. I agree that this is technically wrong, but it does make sense when looking at it in the above context of heating systems.
Yes, over 100% efficiency is exactly what I claimed. In winter, you'll get more BTUs of heat output from a heat pump than you had put in as BTUs of electricity input -- because instead of converting the electricity to heat, it's using the electricity to pull heat from the outside and put it in your house. Hence, it's a more energy-efficient way to do things than the laws of physics would allow for a device that directly converted electricity to heat. That's what it means to be a reversible air conditioner, yes.
IDK why me saying that is some kind of controversial statement -- it's simply a factual description of the product. There are scenarios and real-world constraints which may mean it's more or less sensible to install one, but over 100% efficiency is, exactly, the selling point of a heat pump.
Yes, he pumps do move more heat than the electricity that they consume. That's because they are a heat pump, not an energy conversion system like a motor.
No it doesn't - you're not creating heat, you're moving it. You can move more heat than the amount of energy you expend moving it. Hence the efficiency above 100%
It's a really bad piece of jargon, but is an internally consistent definition. They mean (heat entering building)/(work consumed) > 1
Which is a way if defining efficiency (energy out / energy in), just a really awful and misleading one.
In terms of % of carnot efficiency, the best heat pumps are about where stationary heat engines generally are, 40% or so.
Thank you! It seems to me to be like saying "LEDs are more than 100% efficient because we're applying the same metric of efficiency that we would for incandescent bulbs". They're two different methods of generating heat, why would you use the efficiency rule from one to judge the other?