Enthusiasts and Skeptics,
To give you a basis for analysis, by 2050 the goal is to have forty or so concentrator-photovoltaic space-based solar power (SBSP) satellites in geostationary orbit, each broadcasting via microwave between 2-5 gigawatts of power to terrestrial electrical power grids, with 1-to-5 broadcast antennas that can beam power to as many locations.
This must be done using a sound business case. John Mankins calculates that this can be achieved by keeping the costs of delivery and assembly on orbit below $3,500 per kilogram–keeping the cost to customers below $0.10 per kilowatt/hour. This will drive robotic assembly and tug systems to pull these enormous structures from low orbits to geostationary. On orbit fueling stations will be required. Paul Werbos believes the best way to do this is to get launch costs down below $200 per kilogram. But several other factors help make the business case. For example, if the price of other energy sources goes up it helps to close the business case for SBSP. Other factors include the efficiencies associated with solar collectors, energy conversion, antennas/rectennas, signal path loss, etc. Dennis Wingo and others have suggested that the first customers for space-based solar power will be international–in areas such as India and Japan where the price per kilowatt/hour is astronomical compared to the Americas or Europe. All of this goes into making the business case.