The microwave frequency would be one that is least absorbed by the Earth's atmosphere. People have expressed concern that the beam might damage anything that gets in its path but they claim it would be 1/6 the intensity of noon sunlight. I am not sure how they are comparing light energy to microwave energy. The plan would have the system operating in 2016.
Solaren says that unlike ground-based solar arrays, space satellites could generate power 24 hours a day, unaffected by cloudy weather or Earth's day-night cycle. The capacity factor for a ground-based solar is typically less than 25 percent. In contrast, the capacity factor for a power-generating satellite is expected to be 97 percent.
The agreement calls for 800 gigawatt-hours of electricity to be provided during the first year of operation, and 1,700 gigawatt-hours for subsequent years. The larger figure is roughly equal to the annual consumption of 250,000 average homes.
Very interesting stuff and this year there is really a big emphasis on the "Greening of Wireless" to reduce our dependence on fossil based fuels. Microwave Journal is hosting a webinar and featuring a technical article by Mesuro and Tektronix to introduce a new open loop active load pull technique for the design of complex, highly efficient power amplifiers, necessary for reducing the power consumption of tomorrow’s mobile infrastructure. The method utilizing microwave sampling scope technology to simultaneously capture waveform data ranging from DC to several tens of GHz is demonstrated.