A constellation design for orbiting solar reflectors to enhance terrestrial solar energy

Abstract

Orbiting solar reflectors (OSRs) are flat, thin and lightweight reflective structures that are proposed to enhance terrestrial solar energy generation by illuminating large terrestrial solar power plants locally around dawn/dusk and in night hours. The incorporation of OSRs into terrestrial energy systems may offset the daylight-only limitation of terrestrial solar energy. However, the quantity of solar energy delivered to the Earth's surface remains low due to short duration of orbital passes and the low density of the reflected solar power due to large slant ranges and the projected image of the solar disk. To compensate for these, this paper proposes a constellation of multiple reflectors in low-Earth orbit to enhance the quantity of energy delivered and extend pass durations. Circular near-polar orbits of 1000 km altitude in the terminator region are considered in a Walker-type constellation as a preliminary analysis to avoid eclipses and to include Sun-synchronous orbits. Starting from a simplified approach, equations of Walker constellations describing the distribution of the constellation reflectors is modified to ensure scalable expansion of the constellation by a phasing parameter between the reflectors. Thanks to this approach, a single groundtrack optimisation is sufficient to describe the constellation. This optimisation was carried out for single and two reflectors per orbit, with an objective function defined as the total quantity of energy delivered per day to existing and hypothetical solar power projects around the Earth. When full-scale constellations are considered with 5, 10 and 20 reflectors, the quantity of solar energy delivered linearly scales with the number of reflectors and considerable in the broader context of global solar energy.