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Comment by anthropodie | Hacker News Reader

But what is the effeciency of such a system?

In the first minute of the video they claim “98% storage efficiency.” Not sure exactly what that means though.

This page gives 1% loss per day: https://rondo.com/how-it-works But clearly that's energy in -> steam out, not including any losses from converting from steam back to electricity for example. Although clearly they are targetting first processes that require steam as an input.

Apparently electric heating is 100% efficient from some basic googling. I had no idea this was the case. So maybe the 98% efficiency is not totally bullshit.

No machine has perfect efficiency

The losses are heat. Resistive heating is 100% efficient. Use a heat pump though and you can get to 300%-400% efficiency because you are using the energy to move heat from one place to another instead of turning it into heat.

You’ve got to expound on this a little more because 300-400% efficiency doesn’t make sense.

The comment you're replying to probably meant to say it has a coefficient of performance [1, 2] of 3-4.

[1] https://en.wikipedia.org/wiki/Coefficient_of_performance

[2] https://en.wikipedia.org/wiki/Heat_pump#Performance

Referring to COP as efficiency is an intentionally misleading practise pushed by the heat pump industry that makes communication worse for everyone forever if we accept it and doesn't really help anyone.

Refer to it as COP or as moving 3 units of heat for one unit of input.

Heat goes in. Heat goes out. It's already thermalized.

You can't kill what is already dead.

The right question is how much heat escapes? This will depend on time, and they seem to be claiming 12 hours effectiveness which would seem to imply half of the heat escapes at max storage somewhere between 3 and 24 hours.

No, the right question is "what is the efficiency of the system". It already entirely encapsulates the lesser question of how much heat escapes.

That question has no defined answer. It's like asking 'how many cups of water should I drink'. Or 'how much deisel does my bicycle use'.

It depends on both time and how full it is. Possibly also how full it has recently been as well in the case where it is filled unevenly to reduce loss.

Without anything more specific than '1% loss a day' from their marketing copy, it's difficult to say, but probably "about 90% in typical use" if you want to be even more reductive than that rather than encouraging clear communication.

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