alt Hacker NewsIt isn't just the cost to collect, it is also the cost to store. Heat is easy and safe to store at just above room temperature in rocks - but you need a lot of rocks. Just to heat my house for a few days would need tons of rock at temperatures I'd allow in my house (I have kids and so I worry they will open the rock container and get burnt). Rocks are not free. You can also use water for storage, but again you have the issue needing a tank (and water is a drowning hazard, plus the worry about leaks...)
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markvdb • yesterday at 8:51 PM
Square cube law will optimise heat storage. These Finnish sand based heat batteries are a prime small-scale example.
> Just to heat my house for a few days would need tons of rock at temperatures I'd allow in my house (I have kids and so I worry they will open the rock container and get burnt). Rocks are not free
Sand/rock heat storage is for industrial and utility scale application, not your house.
> You can also use water for storage, but again you have the issue needing a tank (and water is a drowning hazard, plus the worry about leaks...)
Tank heat pump water heaters are available and can already do load shifting on a daily basis (using off peak cheaper and cleaner electricity). I have one and it works great, and I guarantee it isn't a drowning hazard.
There are versions of these systems that can store enough heat to heat a house, not just provide hot water at the tap.