Thanks for the input! I've had several more thoughts:
You're absolutely right about the cost, but it could be contained with refractory cement and would not have to rely solely on metal casings. It seems like buying either in bulk has comparable pricing.
interest problem. I tried to find some info, but there's a lot of engineeting math (I'm an English teacher who also loves the sciences) I don't have the time to sort out right now. I think that using rock wool and refractory cement (see number 1) could help offset this energy loss.
I knew that water could be kept liquid under pressure, but for the purposes of citizen science and making tech more democratic, high pressure systems are a lot of risk and can be devastating when mistakes are made.
Absolutely. And that's the goal of my thoughts. Finding a cheap material that can hold high temperatures and remain solid. The transfer to electricity could be done by using the heated mass to heat a hot pumped liquid or using transfer rods made of a solid material with a high heat transfer coefficient.