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A comment on Giant 'sand battery' holds a week's heat for a whole town. Parent comment

Re:Giant 'sand battery' holds a week's heat for a whole town by noqc on Wednesday March 13, 2024 @10:52PM (#39700131)
Peak solar is peak A/C usage in the summer, which is typically more expensive than heating. In colder times more energy is used at night, but I think less energy is still used at night in the winter than in the day in summer.
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Re:Giant 'sand battery' holds a week's heat for a whole town by fbdab103 on Wednesday March 13, 2024 @11:34PM (#39700353)
That does not seem right.

A hot day in summer might be 35C->20C (95F->68F). Winter is going to be more like -10C->20C (15F->68F) twice the temperature gradient to overcome.

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Re:Giant 'sand battery' holds a week's heat for a whole town by lstodd on Thursday March 14, 2024 @01:43AM (#39700888)
That does not seem right.

-10С to +20C .. I can't even think of a place with such a swing.

Harsh continental climate winter is maybe -30C to -20C or so.

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Re:Giant 'sand battery' holds a week's heat for a whole town by noqc on Thursday March 14, 2024 @01:51AM (#39700914)
he's saying that you need to get the temperature to 20 from -10.
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Re:Giant 'sand battery' holds a week's heat for a whole town by lstodd on Thursday March 14, 2024 @02:35AM (#39701100)
Ah. My bad.

Still, if you got this kind of temperature gradients, and I happen to have lived in such a place, you also got at least 100mm mineral wool insulation or eqivalent. Which is poor by the way, and people do invest into 200 or sometimes 300mm. Which makes CO2 and moisture control more of a problem than heating. You basically either heat the outside via ventilation anyway, or invest into heat exchangers. Since complex HVAC systems come with maintenance burden, people just put up 50-100KW-ish heaters, be it natgas or wood and declare the problem fixed.

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Re:Giant 'sand battery' holds a week's heat for a whole town by noqc on Thursday March 14, 2024 @03:26AM (#39701328)
You could be right, insulation is a lot more effective at keeping houses warm than cold though (greenhouse effect) and heat pumps can dump their waste heat inside.
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Re:Giant 'sand battery' holds a week's heat for a whole town by Newlaptop on Thursday March 14, 2024 @02:01AM (#39700954)
Using the term "energy" here is suboptimal because it's mixing grid electricity with gas power.

A/C tends to be powered from electrical grid. Heat is often from propane or fracked gas.

More energy overall is used to heat homes in cold climates, but cooling homes in hot climates creates the challenging grid demand.

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