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Old 07-04-20, 02:10 PM   #9
NiHaoMike
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1kg of ice will absorb 333kJ of energy. 1kg of the best lithium batteries will store on the order of 800kJ of energy, but cheaper ones will store considerably less. Then there's the efficiency of the heat pump which is already going to be lower than average given the space and weight limitations - COP of 2 would be optimistic.

Doesn't seem worth the cost to get a mere 4-5x the storage per weight even when the best parts are used. Also, making heat pumps smaller makes it more difficult to make them efficient while the efficiency of "discharging" thermal storage remains high until insulation losses become significant.

EDIT: Also, batteries have to be derated to get good lifetime out of them - on the order of 20-80% for lithium leaving 60% of capacity usable. A thermal storage tank can be left at any "state of charge" for an indefinite time with no impact on lifespan.
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Last edited by NiHaoMike; 07-04-20 at 02:48 PM..
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