In a space power system the energy captured from the sun by means of a gigantic solar cell array is relayed to the Earth by means of a microwave beam where the microwave energy is captured and converted into dc power. The capture and conversion processes can be jointly accomplished by a large non-directive aperture several square miles in area made from many small receiving apertures each terminated in an efficient solid-state rectifier. This kind of device, called a “rec-tenna”, has achieved a combined collection and rectification efficiency of over 50% in the laboratory. An overall efficiency of 85% to 90% should be possible with additional development effort. A possible future direction of the evolution of this device for the space power station application is reviewed.