Mirrors in Space for Low-Cost Terrestrial Solar Electric Power at Night

A constellation of 18 mirror satellites is proposed in a polar sun synchronous dawn to dusk orbit at an altitude of approximately 1000 km above the earth. Each mirror satellite contains a multitude of 2 axis tracking mirror segments that collectively direct a sun beam down at a target solar electric field site delivering a solar intensity to that terrestrial site equivalent to the normal daylight sun intensity extending the sunlight hours at that site at dawn and at dusk each day. Each mirror satellite in the constellation consists of a linear string of mirror elements and each terrestrial solar electric field site has a 10 km diameter and can produce approximately 5 GW per terrestrial site. Assuming that in 10 years, there will be approximately 40 terrestrial solar electric field sites evenly distributed in sunny locations near cities around the world, this system can produce more affordable solar electric power during the day and further into the morning and evening hours. The typical operating hours or power plant capacity factor for a terrestrial solar electric power site can thus be extended by about 30%. Assuming a launch cost of $400/kg as was assumed in a recent NASA Space Power Satellite study for future launch costs, the mirror constellation pay back time will be less than 1 year. A logical continuation of this space mirror satellite concept can potentially lead to solar electric power at a cost under 6 (c) over bar per kWh.