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Comment by iainmerrick | Hacker News Reader

Similar technology already in production in the UK: https://www.sunamp.com

They make a molten salt heat battery for homes and businesses. You store excess heat or electricity in the battery, and use it for central heating and hot water. Since you’re not trying to convert it back to electricity it’s very efficient. It basically replaces a large expensive water cylinder with a smallish box.

PS: I have no connection with or investment in Sunamp, I just think it’s a terrific idea. I am a potential customer, though!

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This is not really the same. Malta seems to use a heat pump to produce reservoirs of both hot and cold material. This allows to produce electricity via a carnot process with very high efficiency (theoretically 100% because while the carnot process that produces electricity has an efficiency <1, the heat pump can have a carnot efficiency of >1). In practice they might get to 70% efficiency or so.

Sunamp.com seems to be just ohmic heating for thermal usage of excess electricity.

Are you sure sunamp is molten salt? To me, molten salt is to store energy at a very high temperature in insulated containers.

I thought sunamp is some kind of room temperature phase change material that does not require heavy insulation.

Was going to mention Sunamp.

It does use a PCM, and that is described as a salt so maybe it's where the confusion comes from.

It also has far better insulation than equivalent devices (hot water cylinders). Typically VIPs, although I've read a few reports about the casing being compromised recently and that wouldn't play nicely with the panel.

Yes, I glommed onto the use of “salt” in both cases and figured they were similar.

There are other alternative technologies to store energy as heat, in particular molten silicon:

- https://reneweconomy.com.au/mit-team-gains-ground-on-molten-...

- https://1414degrees.com.au/ (which looks like a competitor for malta)

I’m not at all sure, you’re almost certainly right.

(Not knowing much about the chemistry, I’m naively conflating the two)

Edit to add: Sunamp has non-zero heat loss, so it must be stored hot rather than room temperature, but it might not be very hot.

Sunamp is missing the “cold portion” of the system that Malta has set up, drastically decreasing energy efficiency by not being able to maximize the advantage of heat differentials in the Carnot process.

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