Could a man-made star solve Earth's energy crisis?

Where do we get our energy in the second half of this century? The world’s population is rising and we will need ever more electricity.

Burning fossil fuels is not the answer, given its ability to alter the Earth’s climate. Renewables such as wind, solar and wave might be getting cheaper, but will they ever be enough?

For On Assignment - which airs on Tuesday night - I went to take a look at the most futuristic idea for how to solve our energy crisis, something that is not guaranteed to work but, if it did, could one day save the world.

Set in the serene countryside of Saint Paul-lez-Durance in Provence, I saw the most sophisticated, expensive machine ever conceived taking shape - this is Iter, an attempt by scientists and engineers to recreate a star on Earth.

Stars such as our Sun shine because the hydrogen atoms are pushed together at their cores until, two by two, they fuse into helium - a process that releases a little energy.

For decades, scientists have wondered if we might be able to do something similar on Earth.

What is nuclear fusion?

Nuclear fusion is different to the more familiar nuclear fission, which involves splitting heavy atoms such as uranium and is at the heart of modern nuclear power plants.

Fusion has an almost unlimited source of fuel (in seawater) and its radioactive byproducts stay dangerous for a lot shorter time than traditional nuclear fission (where waste can remain harmful for thousands of years).

But the technical (and political) challenges for fusion are enormous.

Iter is a joint attempt, by 7 partners representing 35 countries, to prove that nuclear fusion could work.

It will boil up heavy versions of hydrogen gas (deuterium and tritium) to around 150 million degrees Celsius inside a vast ring-shaped container, called a tokamak. And all that gas will be kept in place by superconducting magnets, which only work when they are kept as cold as the vacuum of space.

A global solution to a global problem?

The million parts for this machine are being built all over the world.

Sixty miles from the main site for Iter, in Toulon, I visited a giant temperature-controlled warehouse that had been been built at the harbour side location of the French engineering company, Constructions Industrielles de la Méditerranée.

Here, metallurgists were painstakingly making D-shaped, 15-metre-long steel plates that hold the superconducting cables in Iter’s magnets.

The superconducting cables, which are made from niobium-tin, would fly apart under their own immense magnetic field without the structural support of this steel.

Each D-shaped plate started as 24 tonnes of high-grade stainless steel. Inside the warehouse in Toulon, a giant drill spends several months, working night and day, to carve out a spiral of grooves into each side of the plate, shaving away mere thousandths of a millimetre from the metal at each circuit. When it is complete, only 8 tonnes of metal remain.

This is just one piece of the puzzle. The 100,000 kilometres of the superconducting wire for the magnets (enough to wrap around the equator twice) will be made across China, Japan, Russia, South Korea and the US. The magnet itself will be built in China and France. Parts of the tokamak vessel will come from South Korea.

That internationality is reflected in multiple ways: the flags fluttering at the main entrance to Iter’s entrance; a series of small, empty offices in the recently-finished headquarters building, one each for any representatives of the partner nations who might be visiting; a grand, UN-style meeting chamber at the top of the building near the main entrance where the big decisions about the project get made by the organisation’s council members.

That internationality can be seen in Iter's canteen, which buzzes with different languages. I sat down with an Irish fusion physicist who is starting her sixth year with Iter. The enormous technical challenge of making fusion a viable option for everyday energy are not lost on Dr Deirdre Boilson.

'Enormous advantages for humanity'

“Working on this project day to day ok it can be stressful, the tempo is really high,” she says. “The advantages are so enormous [but] for humanity it's a no-brainer that we should be putting energy and effort into this to make it work.

We need this for the future and this is why all these people are here. Everybody here believes that this is the way we should go and that's why I think the seven international partners have all come together… I actually feel goose pimples and I think I am part of this, I have built this. This is an important step towards the future. I love it here.”

Across the road at the vast Iter building site, I met Professor Steven Cowley, who has been working on the theoretical physics of nuclear fusion for three decades and is now chief executive of the UK Atomic Energy Authority (UKAEA), which runs the experiment that was the precursor to Iter, a nuclear fusion reactor in Oxfordshire called Jet.

The last time he had seen the site, there was still mud at the bottom of the main pit. Standing over the recently-finished concrete platform, he pointed to where the super-hot gas will one day start burning and fusing atoms.

“It’s not ordinary by any stretch of the imagination - and when it's working, you know, it will be one of the great wonders of the world.”

On Assignment airs on ITV this Tuesday at 10.40pm