[beepy]

“Lennox International… developed the first prototype that achieved the Technology Challenge’s standards about a year ahead of schedule. The prototype delivers 100% heating at 5°F at double the efficiency, and 70% to 80% heating at -5°F and -10°F.”

The release goes on to say they expect commercialization and deployment in 2024.

[tempestn]

Perhaps I missed it skimming the article, but my question is, double the efficiency compared to what? To the current state of the art cold climate hear pump? Or to a resistive heater?

[martijnvds]

Maybe they're trying to write around the term "Coefficient of performance" (COP) for people who have never heard of heat pumps.

I think a COP of 2 at 5°F (-15°C) is pretty good.

[linsomniac]

COP of 2 at 5F is good. But... Mitsubishi has one that is 3.13 at 5F and LG has one at 2.65 at 5F, so this isn't really the breakthrough that the press release claims, the breakthrough is that a US company is doing it.

[tssva]

That depends on whether the Mitsubishi and LG units meet the other requirements of the competition.

[tssva]

Minimum COP for the competition is 2.1-2.4 at 5°F. No idea what the actual COP for this unit are.

[pkulak]

Yeah, and what is “100% heating”? Do they mean 100% of the capacity? Why do people write things with important words just left out?

My new car can do 100% driving!

[yason]

What they probably meant is that at 5°F the pump can supply 100% of the heat required to keep a house (of certain size) warm, with no other form of heating required. At -5 and -10, it can still extract enough heat from the outside to supply 70-80% of what's needed but you will need other means of heating such as resistive electric radiators to complement the heat pump.

Surely not engineering way of thinking but that's a common heat pump metric for ordinary people.

[2OEH8eoCRo0]

Heat pumps have efficiency > 100%

[lupire]

Efficiency is a misleading word for heating, because the units don't match; they are both energy, but different "type". The denominator is fuel energy lost, but the numerator is thermal energy change within an area of interest. A heat pump moves thermal energy from outside, changing unimportant thermal energy into good thermal energy.

"Coefficient of performance" is a better term.

https://en.m.wikipedia.org/wiki/Coefficient_of_performance

[stormbrew]

This just seems like unnecessary hair splitting to me. Obviously the efficiency of something is subject to the important inputs and outputs involved.

If someone asks: "how efficient is this heat pump at heating my house?" And you start digressing about how that's the wrong question to ask you'll be giving them an impression opposite reality, which is for most people: it will use less electric energy than heat energy it puts into your house, almost all the time.

[hedora]

There are theoretical upper bounds on the COP though. As heat pumps get better, it may some day make sense to say things like "this heat pump is 95% efficient, so there is no point in replacing it".

[ketzo]

Huh, I've always heard the "heat pump efficiency > 100%" but never really understood what that meant. Thanks for the explanation.

So the ">100%" comes from the fact that you're spending less thermal energy than you are moving?

[dghughes]

No OP but yeah heat pumps are very efficient some >300% efficient since you're just "pumping heat" from one place to another not generating it.

Even electric heat alone is 100% efficient no incomplete combustion or degradation over time. Efficient bu much more expensive than just moving heat already in the air.

Ground-source are better for now since they are moving heat from a relatively consistent source the Earth. It's about 15C to 25C one meter down where the ground-source heat pump lines are run.

Generating vs moving heat I think is misunderstood by people or really more likely they just don't care. As long as the bill is low!

[based69]

If you could really move heat 300% more efficiently than using a resistive heater to generate heat, couldn’t you just move a bunch of heat to power a steam turbine and get a perpetual motion machine?

[PaulDavisThe1st]

Slightly more precisely: you're using less energy (in the form of electricity used to run the heat pump) than you are moving into/out of the heated/cooled space.

[Gibbon1]

Yeah take the energy you pump from Reservoir A to Reservoir B divided by the energy requires to do that and that's COP. Which you can think of as an efficiency.

[thedougd]

Exactly.

[OJFord]

No they don't. Just because you don't pay for an input (outside air/the ground/a body of water) doesn't mean it isn't an input.

[joemazerino]

To the current cold pump which can only be efficient at 0 or above. Then you get diminshing returns for the electricity expenditure