[OJFord]

Just because you pay a positive non-zero amount for less than a quarter of the energy in, it does not mean that a device has greater than 100% efficiency, which is not possible.

If heat pumps are 400% efficient then log burners in cabins in the woods are even better.

[jackcarter]

A heat pump warms a home more efficiently than using the same amount of electricity for resistive heating. It can do this because it's not generating the heat from scratch; it's moving heat from outside to inside.

https://en.wikipedia.org/wiki/Heat_pump#Performance

[xattt]

A local company has developed a heat pump with a thermal energy storage system. Not sure how they do this, but I imagine there is some sort of insulated cinder blocks on a secondary loop that shuttles heat/cold to where it needs to go.

(1) https://stash.energy/en/product/

[folmar]

They try very hard not to be specific, but the industrial heat accumulators are usually just water.

[xattt]

> … heat accumulator

Thank you for helping me learn a new HVAC term!

[OJFord]

I know. It's only >100% 'efficient' if you ignore the input of 'outside heat'. That is not a normal calculation, and not really called 'efficiency'.

It's desirable for multiple reasons, of course, but it's not efficiency.

[pmoleri]

Unfortunately by that metric other electrical heaters tend to 0% efficiency because they are not making use of the virtually unlimited energy outside the buildings.

The 400% metric let's you compare with other heaters, the 100% is kind of useless.

[OJFord]

They're not using them as an input, so.. obviously they're not included in the input/output calculation?

[mminer237]

All energy from log burners comes from the fuel, and some ashes remain unburnt. They're under 100% efficient at converting fuel to heat. You put in x fuel and <x heat.

A heat pump takes heat from outside the system. You put in x fuel and you get >x heat. Getting more energy than you put in makes the efficiency over 100%.

[OJFord]

I know. You can't just ignore the bulk of the input and still call it 'efficiency' though.

Even manufacturers call this 'coefficient of performance', not efficiency.

[MichaelCollins]

Since precise use of language is so important to you:

> "You can't [...]"

He did, so obviously he can. You mean shouldn't, not can't.

[OJFord]

Sure, a slightly irritating turn of phrase, not accurate. I didn't think it would be so controversial to hold terms of art/words with actual scientific meaning to a higher standard though.

If we're willing to be so blasé with 'efficiency' then why not, say, 'functional programming'? If it works it's functional right?

[marshray]

An implied qualification of "you can't [while remaining logically consistent]" is common usage.

[bufferoverflow]

> They're under 100% efficient at converting fuel to heat

I think only matter-antimatter reaction comes close to 100%. Burning fuels isn't even 1% of that.

[cedilla]

Impossible in a closed system. Extremely common elsewhere.