Nuclear fusion has the potential to solve the world’s energy crisis with carbon-neutral technology by harnessing the process that drives the Sun. So far, decades of research have generated little more than hype.

The energy needed to stoke the vast temperatures at which such reactions can occur still outweighs the energy they produce, and supposed breakthroughs such as “cold fusion” have turned out to be false dawns. Physicists joke that they have been predicting the technology is “30 years away” for the past 30 years.

The British-led team will use lasers to start fusion reactions that generate more energy than they consume and they have won the backing of an influ-ential EU science panel, The decision paves the way for a seven-year, £500 million programme to construct an experimental reactor based on a revolutionary technique that could make fusion a commercial reality within two decades.

The prototype for the Hiper (high energy laser fusion research) project is likely to be built in Britain, using the world’s most powerful laser to generate temperatures of millions of degrees at which fusion can occur.

A purely civilian facility, it will build on research at a US military laboratory which is expected within the next five years to use a form of laser fusion to produce more energy than it consumes. Hiper will then develop a slightly different laser technique that is more suitable for commercial use.

If it works, laser fusion power stations could be supplying most of the world’s energy needs by the middle of the century, replacing fossil fuels and nuclear fission with a technology that produces next to no greenhouse gases or long-lived radioactive waste.

The Hiper approach has been endorsed by peer-reviewers for the European Commission, which is now negotiating with the scientists over support for the first phase of the project. The EU is also backing a different approach, a reactor to be built in France by 2016 will not use lasers, but conventional “hot fusion” contained by superconducting magnets.

“Fusion is basically nature’s solution to the energy problem,” said Mike Dunne, who leads the Hiper team. “It’s how the Sun and the stars work. We’re just a couple of years away from seeing it in the lab. The public will then be asking what’s next, and we’ll be in a position to take it forward. It is still a way off – this is not going to solve the immediate problem of greenhouse gases. But it should make sure we never again fall into the trap of polluting to meet our energy needs.”

Nuclear fusion involves merging two types of hydrogen atom – deuterium and tritium – to make helium, as well as neutrons that release vast quantities of energy. Almost limitless amounts of deuterium fuel can be made cheaply from seawater, tritium being produced as a byproduct in the reactor itself. Nuclear fusion produces only rudimentary radioactive waste, similar to that from hospital X-ray machines, and none of the high-level waste from fission reactors.

The extremely high temperatures at which the reaction takes place cost large amounts of energy to generate, and require magnetic containment facilities, as terrestrial materials would melt in contact with the reaction. Lasers can be used to create these temperatures efficiently, at the point of fusion, so that containment of the reaction becomes less of a problem.

A pulsed laser with a power of a petawatt (a million billion watts) is directed at a fuel pellet two millimetres across. The vast pressure this creates compresses the pellet to a diameter of few microns and generates temperatures of tens of millions of degrees, allowing fusion to begin.

Professor Dunne, of the Rutherford Appleton Laboratory in Oxfordshire, said: “To put that in perspective, it [the laser] is 10,000 times the power of the entire UK National Grid. And then you’re going to focus that down onto a spot that’s 10 to 100 times smaller than the width of a human hair. The pressure is equivalent to 10 Nimitz class aircraft carriers sitting on your thumb. Some pretty crazy things are going to happen, and that’s what we’re about.”