pump ammonia! Can evaporate at PVC compatible temperature.
A very minor problem with this scheme is the mile thickness insulation needed to not lose much of the sun’s heat to space, on the trip back. A 2nd minor problem is the actual pipe section close to the sun.











First, fusion has 0 theoretical economic potential, but there is some potential for energy gains from 2250* + steam. Water deconstructs above this temperature into powerful HHO gas, that when ignited gains another 2500* that will chain react with higher pressure steam to make the steam even hotter/higher pressure. Minor problem of melting all known turbine material, is avoidable through just higher volume of pressured steam.