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.
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.