These plans need to be reworked because the Bering's mentioned are not all available. But this engine and boiler imstrutions are ment to be built withmosty off the shelf parts. I asked a person that makes solar thermal collector how much collecter to supply this engine on even cloudy days.
The price he quoted was way too high but he stayed it would need 14 square meters of collectors
https://www.greensteamengine.com/
#grownoster