Solar Power Satellites (SPS)

The aim of this chapter is to review and assess the state of the art in electrical technology in 2013 insofar as it relates to any future realisation of solar power collection in space for subsequent delivery to the planetary surface by microwave beams. On the assumption that standard solar photovoltaic panels can be deployed over a sufficiently extensive area to generate gigawatts of DC power, then the relevant technology areas, which will arguably make solar power satellites (SPS) viable, lie largely in the domain of microwave power generation and microwave array antennas. Three power source candidates are addressed in Sect. 9.3, namely klystron and magnetron power tubes and solid-state microwave power amplifiers. The operational principles of each type are reviewed, while their advantages and disadvantages in the proposed SPS application are evaluated. The antenna, which will be required to beam microwave power to a receiving station on the earth's surface, is realisable only in array form, and Sect. 9.4 addresses the alternatives, ranging from slotted waveguide arrays, waveguide phased arrays to micro-strip patch arrays. Again, advantages and disadvantages of each in the SPS context are examined. In addition to power handling, gain and efficiency of these arrays, an exceedingly important requirement is that the microwave beam should remain 'captured' by the ground station. Methods for achieving this are developed in this chapter. Finally, the ground station receiving antenna is required both to capture the microwave beam and to efficiently convert the microwave power to DC power for transmission over the grid to end-users. The favoured approach is based on the rectenna (rectifying antenna) concept which is described in Sect. 9.5.