The proposed structure would be more than double the height of the Burj Khalifa in Dubai

Credit: AFP PHOTO /NASA/HANDOUT

Solar power is notoriously unreliable. The sun may be the solar system’s biggest energy source, putting out more than humanity could ever hope to use, but transforming that into usable power comes up against real-world problems of unreliable weather, a lack of ground coverage and – most troublesome of all – the dark of the night. 

Even if solar were to produce 100pc of the electricity grid’s needs, without a revolution in energy storage the energy source would not be able to provide power during the hours that Britain faces away from the sun. In the winter, that can be more than half of the day.

But what if we could have solar panels that always face the sun, that are immune to the vagaries of British Isles weather, and which could never be accused of blighting the countryside? 

That is the idea behind out-there proposals for a series of giant solar farms floating in space, which are now being considered by the Government. Experts say the systems – each one able to produce power equivalent to a nuclear plant – would provide 24-hour reliable energy and account for a quarter of Britain’s electricity needs.

“A high percentage of renewable technologies rely on where the wind blows and the sun shines,” says Martin Soltau, the space business manager at the engineering and tech-focused consultancy Frazer-Nash, which recently delivered a Government-commissioned report on space-based solar power. 

“There is this increasing realisation of just how very difficult net zero is going to be. We need to look at these more ambitious technologies if we’re going to really deliver that.”

Space based solar power compares well on cost with other renewables

The idea of putting solar farms in space to supply the earth is not new: it was first imagined by the pioneering Russian scientist Konstantin Tsiolkovsky in the 1920s, decades before space launches or satellites. 

Japan has been studying the technology since the 1980s, when scientists at Kyoto University started to crack one of the key challenges of transmitting power over long distances by flying an aeroplane powered with microwave energy.

But a combination of cheaper solar panels, initiatives to solve the climate crisis, developments in robotics and – crucially – cheaper space launches, have started to make the idea seem viable, even competitive with terrestrial energy generation.

The cost of solar cells has fallen by 85pc in the last decade and the cost of putting a satellite in space, thanks to reusable rockets from Elon Musk’s SpaceX, has been on a similar downward spiral. The amount needed to put a kilogram in space sat at almost $20,000 (£14,670) between 1970 and 2000. Since then it has moved closer to $2,000.

“What SpaceX are doing with Starship [the company’s forthcoming heavy rocket], and the economics of that, what Elon Musk is proposing, is transformative,” says Sam Adlen, head of business innovation for the Satellite Applications Catapult, an organisation to boost space research in the UK. “We’ve seen in the last 5-10 years a revolution in space. We’re talking about things that were science fiction 10 years ago.”

Nonetheless, drawing solar power from space would be a gargantuan engineering challenge. The Government-commissioned report, authored by Frazer-Nash and delivered last month, proposes a 1,700-metre wide structure – more than double the height of the Burj Khalifa in Dubai, the world’s tallest building. It would weigh 2,000 tonnes, or roughly six Boeing jets, and orbit the earth at 35,000 km.

Impossible to launch in one piece, the system would instead be sent into space in thousands of “modular” pieces, the size of a desktop computer, that would be slotted together in space by robots.

The solar power satellite

The structure would effectively comprise two giant mirrors reflecting light onto solar panels, and then beaming it to earth using high-frequency radio waves designed to minimise the power lost during transmission. At that point, it would be captured using what is essentially a giant fishing net, full of antennas. Diffraction would mean the net would have to be around 13km by 6.7km, or the size of 12,000 football pitches.

“It needs to be this big contiguous area, you can’t just patch little bits around the place,” says Soltau. “And for that reason, it’s really difficult to see where it could be sited in the UK.”

The proposed answer is to place it offshore, possibly near a wind farm, which would make it easier to plug into the electric grid. Proponents say that despite the huge size, a receiving net would be around a third of the size of a ground-based solar farm that could produce the same power, and 3pc the size of an equivalent wind farm. As for the radio wave transporting that energy, it is expected to be safe – a quarter of the sun’s power at the equator.

The project would be expensive – perhaps too expensive for something that has not been done before. Frazer-Nash has predicted that five systems would cost around £16.3bn to research and then launch, although it claims this would be cheaper per megawatt hour than nuclear or gas plants.

Solar Power Satellite scale

Each system would be able to provide around two gigawatts, equivalent to a nuclear power station. The researchers say a system could be in the sky by 2042 – in time to meet the Government’s 2050 net zero pledge.

Ministers are now considering ways to fund further research. But Britain may be behind the curve, rather than ahead of it. Japan made space-based solar a national priority in 2008, and China has said it plans to launch test stations in the first half of this decade. The European Space Agency and US researchers are also examining the technology.

That could create its own problems. Enormous structures orbiting the planet and beaming power down to earth will require co-operation, both over their positioning and the radio spectrum needed to transmit power.

But if the Government needs grand ideas to get the UK towards net-zero, it couldn’t ask for one much bigger than this.