A series of optimization steps have been carefully followed which lead almost uniquely to a particular collector design. It appears that a fixed (non-tracking) collector which operates at temperatures near or below 200Ge will make the greatest solar energy contribution to U.S. and world energy consumption. Optimization of the design of a fixed collector leads directly to an all glass, evacuated collector tube with optimal (Winston) concentration. A front surface mirror on the inside walls of this collector tube concentrates sunlight on an internal glass absorbing tube coated with a selective absorber