IT POWERS THE STARS, BUT WE CAN’T GET FUSION TO ADD UP

▶ Nuclear fusion offers near-limitless energy, but scientists are struggling to harness it, Robert Matthews writes

For some people it’s the ultimate source of clean energy, capable of saving the world from catastrophe. For others, it’s a scientific pipe dream that will never deliver on its promise.

What’s not in doubt is that nuclear fusion is an incredibly potent source of energy that has powered the Sun and stars for billions of years.

One cubic metre of fuel, which can be extracted from seawater, could power 10 million homes for a year.

The question is whether this stellar power source can ever be made commercially viable?

Last month, the UN’s nuclear watchdog, the International Atomic Energy Agency, brought fusion experts from across the world to Moscow to discuss that question.

The meeting was held amid intense pressure on governments to find viable alternatives to fossil fuels that could make the global economy carbon-neutral.

For more than 50 years, nuclear fusion has been touted as a viable alternative to fossil fuels. Its hydrogen-like fuel is available in virtually limitless quantities, it produces no greenhouse gases or long-term radioactive waste and carries no risk of meltdown.

That list of benefits is now attracting political attention and UK Prime Minister Boris Johnson announced in September that his government would spend £220 million (Dh1 billion) to build a viable fusion power plant “by 2040”.

But for many scientists it was a promise that recalled an old joke: “Nuclear fusion is 30 years away – and always will be”. That quip reflects the seemingly endless quest to solve the challenge of bringing the power-source of the stars down to earth.

Despite its name, nuclear fusion is fundamentally different from conventional nuclear power. Instead of splitting apart atoms of heavy elements such as uranium to release energy, nuclear fusion smashes atoms of light elements such as hydrogen together so hard they fuse together, unleashing far more energy in the form of fast-moving particles.

Slamming into special “blankets” wrapped around the fusion machine, these particles dump their energy as heat, which is used to generate electricity like a supercharged conventional power station.

But while stars achieve fusion by virtue of being huge, with their intense gravity creating the colossal pressures and temperatures needed for atoms to fuse together, doing the same on our planet is far more difficult. It requires a machine capable of heating fuel to temperatures in excess of 100 million ºC.

Such temperatures were first achieved on Earth in the early 1950s in the form of hydrogen bombs. It took another 20 years for scientists to agree a way of doing the same under controlled conditions.

The result was the “tokamak”, a doughnut-shaped device that uses a magnetic field to control the fusion fuel.

In the 1990s, scientists in Oxford succeeded in triggering controlled fusion using one such machine, known as the Joint European Torus. It holds the record for the amount of fusion power generated – registering 16 megawatts for about two seconds in 1997.

Even now, the modest goal of achieving “breakeven” – getting more fusion energy out than is used to trigger the reactions – remains elusive.

Most scientists believe the best hope lies in Iter, a huge tokamak being constructed near Aix-en-Provence in France. But it is not expected to be completed until 2027 and has a price tag of $20bn (Dh73.45bn) – and even then it will never be commercially viable.

Experts at the Moscow meeting suggested it would require almost pathological levels of optimism to think fusion would be economically viable any time soon.

Among the list of challenges discussed were how to change the design of fusion reactors, with the magnetic fields used by tokamaks consuming huge amounts of electricity.

Scientists at Princeton University in New Jersey are exploring a design that could use permanent magnets – the type similar to fridge magnets – while more radical approaches to fusion power are being investigated by private sector start-ups, some of which are backed by billionaires such as Bill Gates and Jeff Bezos.

So far, none have come close to the conditions needed to generate fusion power.

Whether any of them will debunk that joke about nuclear fusion power being forever 30 years away remains to be seen. But as the Earth warms up, we may not have another 30 years to find out.