I wonder if they recover the sodium and run it back through the process.

For that matter, could you maybe put sodium in a sealed container and then heat the whole container? Like a sodium vapor lamp but causing it to glow by throwing heat at it instead of passing electricity through it.

indeed yes; the sodium is added as sodium chloride. in molten form, it wicks along sapphire and alumina surfaces, similar to a candle. it reforms into sodium chloride as the temperature drops below its boiling point -- 1400 C.

we're exploring fully sealed experiments, but, you have to get the heat into the sealed cell somehow.

https://patents.google.com/patent/US12136898B2/en?oq=US12136...