6 ms·
Critical issue with this technology it only really works well with helium.
by RandomWorker 4y ago
Critical issue with this technology it only really works well with helium.
- kragen 4y agono, though helium does have real advantages hydrogen is actually even better iirc but air works too
- andrewflnr 4y agoDifferent issues with that, but maybe no worse than a bottle of kerosene.
- kragen 4y agoa bottle of kerosene might be 500 g, or 21 megajoules according to https://en.wikipedia.org/wiki/Energy_density#In_chemical_reactions_(oxidation) https://en.wikipedia.org/wiki/Energy_density#In_chemical_rea... but 2 ℓ of hydrogen (i don't know how much you'd use in a residential thermoacoustic cooler so that is a guess but probably the right order of magnitude) is only 0.02 megajoules, a thousand times smaller otoh the kerosene doesn't form an easily detonated high explosive if it mixes with air, and the hydrogen does, and 20 kilojoules can still be plenty fatal in an explosion
- moloch-hai 4y agoSeems like N2 would be a better choice unless absolute molecular weight is important. Helium is hard to keep confined. Reading up a bit, it seems like this has to be a traveling-wave device to get the efficiency advertised: standing wave devices seem limited to a Carnot cycle, where a traveling wave device can operate a Stirling cycle.
- makomk 4y agoAbsolute molecular weight is important. Can't remember why off-hand but if I recall correctly there's a pretty substantial efficiency hit from using heavier gas molecules and conventional Stirling engines have a similar issue.
- jfengel 4y agoCould you elaborate on that? I'm curious and thermodynamics was a while ago...
- Nosep82828 4y ago[flagged]
- moloch-hai 4y agoWikipedia will be more helpful here than I can be.
- hasmanean 4y agoYeah a large scale solution involving helium will not scale. Helium cannot be produced by any process other than hydrogen nuclear fusion, and has to be harvested in nature from natural gas wells. Using it in nuclear reactors is one thing, but at home? Since most of the worlds natural gas is in Qatar and Iran, the world will just have a helium resource crunch if this becomes widespread. Maybe a better working gas to use would be ammonia or desiccated propane. Maybe the ultimate solution is to have neighbourhood heating/cooling units that serve multiple and pipe hot/cold water to them.
- fsh 4y agoThis is a common misconception. Helium and hydrogen leaking into ultra-high vacuum systems is a problem since even trace amounts spoil the vacuum. The leakage out of a storage vessel is completely negligible.
- fsh 4y agoThis is not an issue at all. Helium is inert and relatively cheap. Filling the device with a couple hundred liters will cost a few Euros.