@rahmstorf What worries me: Earth currently runs on roughly 2.5kW per person (https://home.uni-leipzig.de/energy/energy-fundamentals/04.htm), if we‘ll be 10 billion as projected that‘s 25TW. And if consumption increases 100-fold as you write, it will climb to 2.5EW. Solar constant is roughly 1kW/sqm. Let‘s say conversion efficiency is about 25%, then we can harvest 250W/sqm. Means we need 10Tsqm for energy production, that‘s about the area of the complete U.S. - realistic?