University of Glasgow

We're reflecting sunlight from space to generate more power on Earth

Reflectors placed in orbit to direct sunlight towards solar power farms on Earth could generate extra energy when needed most and accelerate the global transition to net-zero.

New research from space engineers at the University of Glasgow shows that placing kilometre-wide orbiting reflectors could boost the output of large-scale solar farms by reflecting additional sunlight even after sunset on Earth.

In a paper, published in the journal Acta Astronautica, Glasgow researchers describe how they used sophisticated computer simulations to determine the most effective deployment of orbiting solar reflectors to generate maximum additional power.

The computer models demonstrated that 20 gossamer-thin orbiting reflectors, 1000 kilometres above the surface of the Earth, could enable solar farms to generate power for an extra two hours every day on average. The additional solar power would be particularly valuable at night when electricity demand is high. The improved output could be scaled up even further with additional reflectors or by increasing their size.

The reflectors would maintain an orbit close to the Earth’s terminator line – the boundary where daylight on one side of the planet transitions into night on the other – in an arrangement known as a Walker constellation. Walker constellations are widely used in technologies such as satellite communication systems, where groups of equally-spaced satellites form rings around the planet to ensure consistent communication with the Earth’s surface.

The team developed an algorithm to determine how the reflectors could be arranged in the constellation and angled to catch the sun’s rays most effectively, maximising the additional sunlight reflected to solar power farms around the Earth in the early morning and late evening.

Our researchers found that the 20 reflectors could generate an extra 728 megawatt-hours (MWh) of electricity per day – the equivalent of an additional large-scale solar power farm on Earth without the associated cost of construction or terrestrial footprint.

The paper is one of the outputs from SOLSPACE, a University of Glasgow-led research project supported by €2.5m (£2.1m) in funding from the European Research Council.

Professor Colin McInnes, SOLSPACE’s principal investigator of the paper, said: “The idea of orbiting solar reflectors isn’t new – in fact, it predates even the space age, as the idea of illuminating cities with light from space was first discussed in the late 1920s.

“However, space reflectors have only been demonstrated once, back in the early 90s, when a 20-metre aluminium-foil reflector was released from the Russian Mir space station to reflect sunlight back to Earth.

“The SOLSPACE project is working to devise, develop and demonstrate ideas for orbital reflector technology that could work on a much more ambitious scale to deliver global clean energy services.

“Tackling the challenges of climate change requires big ideas. While this is undoubtedly a big idea, it builds on technologies that are already well-understood and computer models like ours show how they could be scaled up. In addition, the falling cost of launching payloads to space opens entirely new possibilities for the future.”

Co-author of the paper, Dr Onur Çelik, from the James Watt School of Engineering, said: “Solar power has the potential to be one of the key accelerators in our race to reach net-zero, helping us to mitigate the global impacts of climate change by reducing our reliance on fossil fuels.

“The price of solar panels has dropped quickly in recent years, increasing the pace of their adoption and paving the way for the creation of large-scale solar power farms around the world.

“One of the major limitations of solar power, of course, is that it can only be generated during daylight hours. Putting orbiting solar reflectors in place around the Earth would help to maximise the effectiveness of solar farms in the years to come. Strategically placing new solar farms in locations which receive the most additional sunlight from the reflectors could make them even more effective.”

‘A constellation design for orbiting solar reflectors to enhance terrestrial solar energy’ is published in Acta Astronautica. The research was supported by funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 883730).