One more point seems pertinent. A decade ago we were all lectured that the environment would be best served as we de-materialized society. That is, we would reduce our environmental footprint as we used less matter; reducing the energy inputs and associated pollution that processing materials requires. Renewable energy with the low energy density of its sources, and the storage it requires and using many advanced and rare materials, are taking us the other direction. Instead of depending on dispatchable energy sources which can supply a kilowatt per kilogram of material, we are proposing systems which provide a mere watt using tens of kilograms. We will re-materialize society.