Space: one small step for space solar farms, one giant leap for the climate?
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The record budget of more than 17 billion euros that the European Union granted on Wednesday to the European Space Agency should in particular make it possible to explore the possibility of installing farms of solar power plants in space. An increasingly popular idea because it would better fight against global warming, according to its promoters.

It is a sharply increased budget that the European Space Agency (ESA) obtained from Brussels. EU Member States validated, on Wednesday 23 November, an envelope of 17 billion euros over three years – i.e. 17 % more than in 2019 – so that Europe’s space arm can “stay in the race” against the Americans, the Chinese or even the Russians, said Josef Aschbacher, the director general of ESA.

To obtain these funds, the Agency had dangled new missions to the Moon, to Mars, and to a denser European constellation of satellites. In its boxes, it also has other more confidential projects, one of which could, according to its promoters, help both to fight against global warming and contribute to energy independence from hostile countries such as the Russia. Just that.

The tallest structure ever built in space

The program in question Solaris, aims to generate energy in large quantities from huge farms, or solar power plants, in space that would stretch almost 2 km in length. “It would be the largest structure ever built in space, about 1,000 times the size of what has already been built there,” said Sanjay Vijendran, the physicist in charge of the Solaris program within the ESA.

Space solar farms have been a dream of astrophysicists since the concept was first formulated in the 1970s. It involves building thousands of solar panels to send them into orbit more than 30,000 km from the Earth. Earth, to capture the sun’s rays – like a traditional solar farm – and then transform them into “microwaves which would be transmitted to relay antennas on the ground capable of transforming them back into electricity in order to supply the network”, summarizes Andrew Wilson, researcher at the Spatial Concepts Laboratory at the University of Strathclyde in Glasgow and co-founder of Metasat UKa start-up that is particularly interested in space energy issues.

A project that can give the impression of being science fiction. In a sense, it is. Moreover, the ESA is not yet asking to finance the creation of these space farms. “For the moment, we only want to be able to carry out a feasibility study for three years”, specifies Sanjay Vijendran. A first course of which we only know the approximate cost: a few tens of millions of euros.

Sanjay Vijendran really hopes that this step will be validated in order to be able to remain competitive. Indeed, he assures that “technologically we master most of the steps”, and that more and more countries are starting to get into the heart of the matter. In the United States, Caltech University wants to deploy a first prototype of solar collectors for space in Decemberwhile China plans to send one into space in 2028. The United Kingdom, meanwhile, has decided in July 2022to inject three million pounds (3.47 million euros) to help research and start-ups get a little closer to the sun and its energy.

Capture the sun’s energy 24/7

A race for the space solar farm which is partly due to “the climate emergency”, believes Andrew Wilson. “COP27 demonstrated that current investments in renewable energy may not be enough to meet our commitments to reduce greenhouse gas emissions,” he points out.

Space solar farms could help raise the bar, believe the defenders of this technology. It is a 100% renewable solution and, “unlike solar and wind energy on Earth, it is not intermittent”, explains Sanjay Vijendran. In other words, these farms that float above the clouds can “harvest energy continuously, except during rare periods of solar eclipse”, notes Andrew Wilson.

An advantage over onshore solar and wind power. “When it is dark or the wind is not blowing, there is no creation of solar or wind energy, which means that storage units must be built in order to ensure a continuous supply of electricity. But we absolutely do not know if we will be able to build them of sufficient size for these renewable energies to completely replace fossil sources”, specifies Sanjay Vijendran.

The war in Ukraine would also have “made it possible to become aware of the risk of energy sources linked to a territory which can lead to quasi-monopolies, as in the case of Russia in Europe”, continues Andrew Wilson.

Space farms could be managed by the international community and with receiving antennas installed all over the world. It might then be possible to respond quickly to emergency situations. “For example, if there was a natural disaster completely depriving a country of electricity, we could redirect all the satellites that transmit solar energy to this area”, wants to believe Andrew Wilson.

Finally, rockets aren’t as expensive as they used to be. SpaceX and its reusable launchers have been there. The addition is therefore no longer as salty. “In the past, estimated prices were up to $10,000 per kilogram sent into space, while modern launchers can bring costs down to around $2,000 per kilogram,” says Andrew Wilson.

The cost and the technological challenge

Despite these significant savings, cost remains a major obstacle. One of the most recent estimates – made in 2014 by the US government – estimated that it would take “several tens of billions of dollars to launch all the solar panels into space”.

But this is not the only problem, recognizes Sanjay Vijendran. The other uncertainty relates to the gigantism of such an enterprise. “We were able to prove that all the necessary technologies worked, but we still have to be able to control everything on such a large scale”, he summarizes.

Thus, the assembly of the solar panels will have to be carried out by autonomous robots in space. “We know that it works, but this is a gigantic project, and it’s a hell of an engineering challenge”, underlines the head of the ESA Solaris program.

Ditto for the cableless transfer of energy from space to Earth. “A month ago, the feasibility was demonstrated, but over a much shorter distance,” notes Sanjay Vijendray. A wireless transfer of energy has been carried out in a laboratory of the aeronautical giant Airbus in Munich (Germany) between two points 36 meters apart. The electricity thus generated was used to illuminate a small-scale village. But it is still necessary to manage to do the same over a distance of more than 30,000 km.

For some, these challenges mean that solar power plants in space are still the sweet dreams of scientists. “It’s as fascinating as it is speculative. Between technological doubts and the question of cost, wouldn’t it be better to accelerate and increase investments in green energies such as wind and solar? [terrestres] ?”, wonders Doug Parr’s Twitterthe chief scientist of Greenpeace in the United Kingdom.

For Sanjay Vijendray, this program is a bad case: “We never said that we had to replace existing investments in terrestrial renewable energies, but [qu’il fallait] add these space solar panels in the energy mix thanks to additional financing.”

Andrew Wilson recognizes that this is a very large undertaking, but “we might as well get started quickly if we want to put the odds on our side to reduce emissions sufficiently by 2050”. “It’s a bit like the Three Gorges Dam [la plus grande centrale hydroélectrique au monde, située en Chine, NDLR] as for ambition… except that space solar farms will benefit everyone”, he concludes. It will even be possible to use them to supply electricity to the Moon, specifies the ESA.

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