ED: Hospital autoclaves also use superheated steam, and often at 30(+) psi. But they cost a lot, both to buy and to run...
Yes, it would be very complex to try and install and run a hospital autoclave. 30+ PSI - makes sense if you want to get something else to 20 PSI steam then you better have a bit of extra headroom to get there.
Your design really appeals to me though because I have solar panels on the roof and elecricity is free during the day. The real problem is I doubt I have the skills for it.
Look up "evacuated tube heat pipe solar technology". You can get some serious heat and efficiency from a roof installation.