> Your kettle can do that reliably, we can do this for a huge battery. Scale is important here, as you'd need an array of sensors immersed in the water so that

> Your kettle can do that reliably, we can do this for a huge battery. Scale is important here, as you'd need an array of sensors immersed in the water so that there's no local pocket of close to boiling temperature. > There is always going to be water that will be evaporating when you heat the sand in the middle and condensing on the sides that are cold. That's a slow process, but even if - as long as the temperature is considerably above ambient the water will condense elsewhere. > There is no possibility of scale when you do not heat water to boiling. Actually it forms at temperatures as low as 28 °C.