like a solar hydrogen fuel cell

Lonnie Johnson appears to have invented a source of Solar Heat Electric Power. If it works it seems like it would be pretty amazingly efficient and this article makes it clear it works. I can't wait to see what kind of end product they produce. And if I'm reading this right the only part of it that is hard to make is the ceramic membrane so depending on the pressures involved it might not be difficult to just build one of those if you had the membrane.