A group of scientists from the University of Glasgow has suggested using lightweight orbiting reflectors powered by photovoltaics to increase electricity generation in solar power plants located on Earth.
Through their work, the researchers defined a single reference architecture for orbiting solar reflectors, as well as a detailed analysis of the integrating orbital dynamics, attitude control, and structures. They also assessed the breakeven conditions of these systems in terms of energy prices, launch costs, and discount rates, while noting that the proposed architecture is representative of current or near-term developments in both the energy and space sectors.
They specified that the orbiting reflectors may be particularly beneficial for terrestrial solar power generation at dawn and dusk when there is less sunlight and output is low.
The reflectors are assumed to be built with triangular elements, which the research group said have the advantage that a structure of any arbitrary size can be constructed with them. “Moreover, in the case of membrane tearing, only a single triangular module would be damaged, rather than the entire structure,” it explained. “Developments of the SpaceX Starship reusable launch vehicle will be considered for the transportation of materials and components to space.”
The reflectors would have a hexagonal shape and a diameter of approximately 1 km. They would also be based on multiple mirrors in formations and would utilize control moment gyroscope (CMG) rotors, while operating at an altitude of 884.59 km and being able to perform 14 orbits per 24-hour cycle.
“A hexagonal reflector has been considered for its versatility for in-orbit manufacturing and assembly, where it is assumed that the shape would be assembled from the equilateral triangular elements with 50m side length,” the academics stated. “A combination of the shape requirement and actuator constraints eventually leads to an overall hexagon side of 250m.”
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The research team considered different planned or operating giant solar power plants to validate their approach and said that the world's largest solar project under development – the $20 million Sun Cable project in Australia – may be considered an exemplary solar power plant for the proposed technology.
“This paper considers inclined orbits, but the orbit is selected such that it is ‘anchored' to the Sun Cable solar farm,” it also noted. “The reflectors in this orbit can service nine large solar power plants over one sidereal day, delivering a total quantity of 283.8 MWh solar energy.”
Their cost analysis also highlighted that this technology may achieve an average cost of additional electricity of $70/MWh at a 5% discount rate over a 20-year period. “If a more realistic discount rate of 15% is used, then the same target price can be achieved by reducing the reflector mass density to approximately 13.2gm-2,” they concluded. “Even though this value is smaller than that found in this paper, it is expected that future advancements in space technology may lead to a reduction in the mass density, with the additional advantage that smaller actuators can be used for the same reflector size.”
They presented their findings in the paper “A reference architecture for orbiting solar reflectors to enhance terrestrial solar power plant output,” which was recently published in Advances in Space Research.
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