Wish upon a ‘star in a jar’: The promise of nuclear fusion

WHAT makes the Sun shine? The answer lies in a simple reaction deep in its core.

At temperatures of 15 million deg C and under huge gravitational forces, hydrogen atoms within the Sun collide with each other to form helium. A tiny bit of mass is converted into an immense amount of heat and light.

This process, known as nuclear fusion, produces enough energy to keep the stars shining for billions of years. Our Sun itself has been burning bright for about 4.5 billion years (and don’t worry, it still has another five billion years to go).

Now imagine if we could build a star in a jar, right here on Earth, to harness such unlimited, clean energy. It sounds like material for a science-fiction novel, but efforts are indeed underway to develop nuclear fusion technology, sometimes also dubbed as attempts to engineer an “artificial sun”, in places including the UK, Europe, the US and China.

The process requires two heavier variants of hydrogen: deuterium and tritium. But these aren’t too difficult to obtain; deuterium can be harvested from seawater, while tritium can be produced using lithium, the soft metal found in our gadgets’ batteries.

In fact, just a bathtub of water and two laptop batteries would provide enough fuel to power one person’s energy use for 60 years.

I learned this bit of trivia from Professor David Gann, chairman of the UK Atomic Energy Authority, in a dialogue we had at deep tech investment firm SGInnovate last month.

Prof Gann is one of the leading advocates for nuclear fusion, helming the UK’s efforts to make its mark in this field. In his presentation at SGInnovate, he highlights that this could be the way forward for our transition away from carbon-intensive fossil fuels.

Referencing the analogy on the bathtub and laptops, he says that this “really is very, very little resources” compared to thousands of barrels of coal, for example.

There are also advantages over current nuclear power plants which rely on a different process, nuclear fission, where uranium atoms are forced apart. Unfortunately, fission power has developed a bad reputation for the risk of runaway reactions leading to catastrophic accidents, health risks and radioactive waste leaks.

Fusion power in contrast is safer, as the reaction is self-limiting, can be halted within seconds and does not produce radioactive waste. Fusion plants also cannot be used to produce weapons, according to the International Atomic Energy Agency.

It’s efficient too. Fusion power could generate four times more energy than fission for every kilogram of fuel, and four million times more energy than oil or coal.

Hotter than anywhere in the galaxy

There is a catch though: It takes a temperature 10 times higher than the core of the Sun to make fusion reactions happen.

“We’re talking about putting the Sun in a bottle, in a little vessel on Earth. And the Sun is a very big object with a lot of gravitational forces; it’s that force that allows the fusion to happen. We can’t create those sorts of forces in that way on Earth, and so we have to use much higher temperatures,” Prof Gann explains.

It sounds like a formidable challenge, but I would not underestimate the power of engineering innovation. Researchers have built tokamaks, a doughnut-shaped device, that can heat the fusion fuel to those mind-blowing temperatures.

Just outside Oxford in the UK, scientists are running a fusion machine at 150 million deg C, shares Prof Gann. “A little machine in the south of Oxfordshire, is hotter than anywhere else in the galaxy,” he quips.

So when will fusion power become a reality? Many believe that the technology is still decades away, as it has been difficult to produce a net energy gain, meaning that the process produces more energy than it consumes.

But a breakthrough last year has stirred hope. In December, scientists in a US lab achieved a net energy gain for the first time, by using the world’s biggest laser to bombard a small pellet of hydrogen plasma.

For all the excitement, some are still disappointed. The net gain was only 0.4 megajoules of energy, enough to boil the kettle for my morning coffee.

As with many scientific breakthroughs, awaiting fusion power will require plenty of patience. We probably also have to acknowledge that this technology isn’t going to save us from the current climate crisis; other solutions will be needed to replace fossil fuels in the near term.

But this doesn’t mean we should stop dreaming of stars in jars – one day, they could be powering the world.

The race to “bottle the Sun” is just one of many weird and wonderful phenomena out there that can teach us plenty about the world we live in. Every month, this column will go off tangent from the news and look into more curiosities in various fields, from finance and economics to science and psychology, or even beyond.