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Finland warms up the world’s largest sand battery, and the economics look appealing
(techcrunch.com)
this post was submitted on 17 Jun 2025
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Conversions tend to be inefficient, but in this case you can use only the best kinds of conversions.
They’ll use cheap electricity to heat up the sand, which is approximately 100% efficient. Then, the heat is stored for a while, and that’s when some of it will leak through the walls. Not a whole lot though, because of insulation and a small surface to volume ratio. Eventually, the heat is used to heat up water, which is another highly efficient conversion.
If you convert another form of energy back to electricity, you tend to lose a lot of it as heat. Physics just loves to use heat as the final destination for all sorts of energies, so it only makes sense to aim for utilizing it instead of treating it as a byproduct.
H2 makes the best long term electrical storage, because not only is it more efficient than other cheap alternatives, it can be even more efficient with heat use, and it is economically transportable/exportable and so is not capped by utilization/capacity constraints.
heat storage is extremely useful for complementing winter solar in low winter sun places. Including at small scale. Hydronic floor heating is most efficient use of heat. Heat pumps can very efficiently gain 30C of temperature gain. Sand and construction waste box with water pipes, and heat resistors, flowing through it, can store heat well above 100C that water doesn't ineffienctly. 2000 liters of just water is sufficient in most locations with a fireplace or EV backup, but sand/dirt/gypsum of 500L to 1000L significantly boosts resilence and heat capacity.