Written by Sarah Kellett
Can we power our homes with the process that powers stars? Nuclear fusion offers to do just that, and scientists are looking for ways to harness this energy with experiments that run hotter than the Sun.
The engine of stars
The Sun is heated by fusion – a process where the nuclei of two small atoms, such as hydrogen, fuse together into a larger one, such as helium. This releases a heap of energy. Making fusion work on Earth is a challenge scientists are working to meet. “In the Sun, gravity holds it all together,” says John Howard, from the Australian National University. “We don’t have enough gravity on Earth. Instead we can build a magnetic thermos flask to hold it together.”
The Australian Plasma Fusion Research Facility was upgraded last month to better understand the physics of fusion. Based on a type of magnetic bottle known as a stellarator, the machine uses radio waves and microwaves to heat gas until it forms plasma hotter than the centre of the Sun. “The reason it has to be so hot is because there’s so little of it there. It’s just a puff of gas in that machine,” says John.
Fusion for the future?
The Joint European Torus in the United Kingdom showed that fusion really can provide us with energy. Using the same heavy hydrogen fuel mix, with a bigger machine, it produced 16 megawatts of energy in 1997 – a world record!
The technology could work, but we’re not plugging in yet. “There are still some big technical challenges before you have a machine that can release power steadily back to the grid,” says John. The next leap forward in fusion research is ITER – a huge international project with a massive machine being built in France. Its goal is to produce 500 megawatts of power.
With the power of stars inside, is fusion safe? All current nuclear power stations use another process called fission, which breaks large atoms into smaller parts. Scientists say that fusion is safer than fission. “With fusion, there’s no chain reaction, it will never get out of control,” says John. “If you take the fuel away, it just stops.” Boyd Blackwell, who oversaw the upgrade of the Australian facility, agrees. “You’re talking about much smaller quantities and risk scenarios that are on a much less likely scale than fission,” says Boyd.
Want to explore the maths behind fusion? Read about the donut-shaped magnetic fields inside most fusion reactors.
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Powering our homes and cities is a big job, and scientists are looking for all sorts of alternatives to fossil fuels. What do you think is the biggest issue for the future of energy?
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