The power of stars
Breakthrough means starlight may soon fuel our homes
LAST year, scientists made an artificial star. It was a tiny star and it lasted less than a billionth of a second, but it might just change how we all live.
The scientists were working at the National Ignition Facility; not something out of a Marvel blockbuster, but a physics lab in California. Most of the building is taken up by 192 enormous lasers and the generators that power them.
The beams from those lasers are focused into a tiny chamber the size of a fingernail, where they heat a pea- sized pellet that contains two different forms of hydrogen called deuterium and tritium.
The lasers heated that fuel to over 100 million degrees centigrade and compressed it to the size of a grain of sand.
For a fraction of a second, that created an environment like the heart of the sun.
Stars, our sun included, are nuclear powered. But their nuclear power works in the opposite way to nuclear power stations on Earth.
Nuclear power stations make their energy by splitting uranium atoms. It takes a lot of energy to hold the nucleus of a uranium atom together. If you split it, some of that energy is released and you can capture it to generate electricity.
That process is called fission and it’s relatively easy to do. That’s why we were able to build nuclear power stations in the 1950s, long before other advances like personal computers or the internet.
The nuclear power that happens in stars is different. It’s called fusion and it involves joining small atomic nuclei together. But that’s very hard to do.
There are two opposing forces in an atomic nucleus. One, the nuclear force, tries to bind it together. The other, the electromagnetic force, tries to push it apart. And unless the particles that form the nucleus are already very close together, the electromagnetic force will win. But heat them enough – to millions of degrees centigrade – and you can overcome their repulsion and get them close enough for the nuclear force to kick in and glue them together. When that happens, energy is released. And in the California breakthrough, for the first time, a fusion reaction here on Earth gave out more energy than it consumed. If we can scale that up, the advantages of fusion power could be immense. It could be cheaper, cleaner, and safer than current nuclear power.
The main by- product of this kind of fusion is helium – a harmless gas that occurs naturally in the atmosphere.
Fusion doesn’t produce the highly radioactive long- lived waste that makes current reactors controversial. The nature of a fusion reaction means that the kind of nuclear meltdown and radioactive fallout that happened in Chernobyl is impossible.
So why isn’t nuclear fusion powering your kettle right now?
It’s not for want of trying. Scientists have been working towards commercial fusion for over sixty years. The NIF spent $ 3.5 billion to get its pellet of hydrogen burning. And in Europe a demonstration reactor called
ITER will cost € 20 billion before it’s even switched on.
The costs are huge because the technical hurdles are enormous.
The incredible temperatures needed to get fusion started mean no physical material could contain it. So scientists have developed new ways to hold the burning fuel. In California they use ‘ inertial containment’ where the forces compressing the fuel hold it in place. In ITER they are using vast superconducting magnets to create an invisible doughnut- shaped bottle from pure magnetism.
While fusion doesn’t produce the same sort of nuclear waste, the interior of the reactor will still be full of intense radiation so every bit of control and maintenance will have to be done by robots.
The technical challenges make some scientists sceptical whether commercial fusion will ever be viable. And others believe the money could better be spent on accelerating green technologies.
But many believe that the promise of almost limitless clean energy makes the challenges worthwhile and that fusion should be a key part of a green energy future alongside renewables.
ITER is scheduled to start producing power by 2035. So, if all goes well, we may not have too long to wait before the water for your morning tea or coffee is heated with electricity generated by the power of starlight.
To explore our energy options, visit Glasgow Science Centre’s Powering the Future Exhibition.