Looks like it's creating a standing pressure wave and then tapping into the colder or hotter part as appropriate?
Based on the diagrams it seems like it would need a radiator or something for larger surface area?
Also curious as to how loud it is.
Source: https://www.pv-magazine.com/2023/01/02/residential-thermo-ac...
Which I just noticed was posted a few hours ago, here: https://news.ycombinator.com/item?id=34233719
Sounds like that can be a bit annoying
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“The sound our system produces stays confined inside the core, so you cannot hear it from outside,” said Loyer.
To be even quieter than that is remarkable, IMO.
You'll see them sold under the EcoCute name. Daikin, Panasonic, and Corona (no relation) make them. They get used for homes meant to only have water and electricity hookup, called "all electric" homes.
As user Danieru replied the heat pump is a a Japanese import (although the tank and rest of the system is locally made).
Even your TNT figure has a distance indication. Pressure decreases with the square of the distance when it dissipates as a sphere. Doubling the distance = -6 dB
¹ 20*log(k)=180 => k=1e9, factor to reach between rest state and max pressure, I think.
It's a really cool application of the ideal gas law: PV = nRT where the sound is really playing with the pressure (P) using sound so various parts of the chamber have different temperatures (T).
"Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper."