Energy supply and demand issues are explored and a rationale is presented for increasing reliance on the inexhaustible energy radiated by the Sun. The potential of solar energy to meet global energy needs is surveyed and the objectives for solar energy conversion in space for use on Earth are given. The concept of the solar power satellite, SPS, is introduced, and its advantages for the generation of continuous power compared with terrestrial solar energy conversion methods, are discussed. The technology options for converting solar energy in space, transmitting power, and converting it on Earth into electricity, are summarized. The requirements for space transportation systems, orbital assembly and maintenance are reviewed. The economic, environmental and societal issues inherent in the development and future implementation of the SPS concept, are highlighted. Possible organizational structures which would permit international participation in an SPS program, are presented. The conclusion is drawn that assessment of the technical, economic, environmental, and societal issues has not identified a single constraint which would preclude continuation of the SPS R+D program. This program could lead to a future decision to implement this major option for power generation on Earth. Comments on the National Research Council's report on the SPS are included.