A major breakthrough has been announced by US scientists in the race to replicate nuclear fusion.
Physicists have followed the technology for decades because it promises a potential source of nearly unlimited clean energy.
On Tuesday, researchers confirmed they had overcome a major barrier: producing more energy from a fusion experiment than was put into it.
But experts say there’s still some way to go before fusion drives homes.
The experiment took place at the National Ignition Facility at Lawrence Livermore National Laboratory (LLNL) in California.
Nuclear fusion has been described as the “holy grail” of energy production. It is the process that powers the sun and other stars.
It works by taking pairs of light atoms and forcing them together – this “fusion” releases a lot of energy.
It is the opposite of nuclear fission, which splits heavy atoms apart. Nuclear fission is the technology currently used in nuclear power plants, but the process also produces a lot of waste that continues to emit radiation for a long time. It can be dangerous and should be stored safely.
Nuclear fusion produces much more energy and only small amounts of short-lived radioactive waste. And more importantly, the process produces no greenhouse gas emissions and thus does not contribute to climate change.
But one of the challenges is that forcing and holding the elements together in fusion requires very large amounts of temperature and pressure. So far, no experiment has managed to produce more energy than the amount put into it to make it work.
The amount of energy they generated in this experiment is small – just enough to bring a few kettles to a boil. But what it represents is huge.
The promise of a fusion-driven future is one step closer. But there is still a long way to go before this becomes a reality.
This experiment shows that science works. Before scientists can even think of scaling it up, it needs to be iterated, perfected, and significantly boost the amount of energy it generates.
This experiment has cost billions of dollars – fusion is not cheap. But the promise of a source of clean energy will certainly be a great incentive to meet these challenges.
California’s National Ignition Facility is a $3.5 billion (£2.85 billion) experiment.
It puts a small amount of hydrogen in a peppercorn-sized capsule.
Then a powerful 192-beam laser is used to heat and compress the hydrogen fuel.
The laser is so strong that it can heat the capsule to 100 million degrees Celsius — hotter than the center of the sun, and compress it to more than 100 billion times that of Earth’s atmosphere.
Under these forces, the capsule begins to implode on itself, forcing the hydrogen atoms to fuse and release energy.
Announcing the breakthrough, Dr. Marvin Adams, deputy administrator for defense programs at the US National Nuclear Security Administration, said the lab’s lasers delivered 2.05 megajoules (MJ) of energy to the target, which then generated 3.15 MJ of fusion power output.
Dr. Melanie Windridge, CEO of Fusion Energy Insights, told the BBC: “Fusion has been exciting for scientists since they first discovered what causes the sun to shine. These results have really set us on the path to commercializing the technology.”
Prof Jeremy P. Chittenden, Professor of Plasma Physics and Co-Director of the Center for Inertial Fusion Studies at Imperial College London called it “a real breakthrough moment” proving that “the ‘holy grail’ of fusion can indeed be achieved”.
This is the sentiment echoed by physicists around the world, who praised the work of the international scientific community.
Prof Gianluca Gregori, Professor of Physics at the University of Oxford said: “Today’s success rests on the work of many scientists in the US, UK and around the world. Now that ignition has been achieved, not only fusion energy is being unlocked, but also opens a door to new science.”
When asked how long it will be before fusion can be used in power plants, Dr Kim Budil, director of LLNL, said there were still significant hurdles but that: “with joint efforts and investment a few decades of research into the underlying technologies us in a position to build a power plant”.
This is progress since scientists said 50 – 60 years in answer to that question.
One of the main hurdles is reducing costs and scaling up energy output.
The experiment could only produce enough energy to boil about 15-20 kettles and required billions of dollars in investment. And while the experiment got more energy out of it than the laser put in, that didn’t include the energy needed to run the lasers — which was far greater than the amount of energy the hydrogen produced.