The big idea: will fusion power save us from the climate crisis?

One look at your energy bills this winter might have convinced you that the 1950s idea that electricity would, in the near future, become “too cheap to meter” was not so much a false promise as a sick joke. That over-excited claim was prompted by hopes that nuclear fusion – the process triggered in an uncontrolled manner in hydrogen bombs – would soon be harnessed for power generation. In the type of nuclear power we have today, disintegration of radioactive atoms such as uranium produces heat but also a troublesome legacy of radioactive waste that will stay active for millennia. Fusion power plants would instead generate energy using the same process that powers the sun: fusing of the dense nuclei of hydrogen atoms, releasing some of the formidable energy held in the atomic nucleus, with only helium as the byproduct, and without the pollution.

Today the allure of fusion energy lies not so much in its price as its almost negligible carbon emissions, and therefore its potential to save us from the ravages of global heating. But will it arrive in time to stop the planet frying?

What is nuclear fusion and what have scientists achieved?

There are plenty of uncertainties and unknowns around fusion energy, but on this question we can be clear. Since what we do about carbon emissions in the next two or three decades is likely to determine whether the planet gets just uncomfortably or catastrophically warmer by the end of the century, then the answer is no: fusion won’t come to our rescue. But if we can somehow scramble through the coming decades with makeshift ways of keeping a lid on global heating, there’s good reason to think that in the second half of the century fusion power plants will gradually help rebalance the energy economy.

Perhaps it’s this wish for a quick fix that drives some of the hype with which advances in fusion science and technology are plagued. Take the announcement last December of a “major breakthrough” by the National Ignition Facility (NIF) of the Lawrence Livermore National Laboratory in California. The NIF team reported that, in their efforts to develop a somewhat unorthodox form of fusion called inertial confinement fusion (ICF), they had produced more energy in their reaction chamber than they had put in to get the fusion process under way.

Problem solved? Sadly not. As NIF scientists readily admitted, the energy generated by super-intense laser needed to spark fusion was less than a hundredth of the total amount of energy consumed by the lasers themselves. So they still have to do about a hundred times better to break even. And that’s even before factoring in the energy losses in converting the heat created by fusion into electricity. What’s more, the hi-tech pellets containing special forms of hydrogen used as fuel each cost more than $100,000, whereas a working ICF reactor would need to burn up 10 pellets a second at a cost of less than $1 each.

ICF has so far been little studied as a source of energy anyway; NIF’s principal mission is to study nuclear reactions in order to help maintain the US stockpile of atomic weapons. Most work on fusion energy uses a different approach called magnetic confinement, in which the fuel – at temperatures of around a hundred million degrees, several times hotter than the centre of the sun and fiery enough to melt any material instantly – is suspended by magnetic fields, typically in a large doughnut-shaped chamber called a tokamak.

Making and operating such a device raises eye-watering engineering challenges, with which fusion scientists and technicians have been grappling for decades. Many current hopes are pinned on the International Thermonuclear Experimental Reactor (Iter) being built in southern France. As the name suggests, Iter won’t be a power plant – it is strictly an experimental facility, its goal being to solve some of the engineering problems so that we can work out what a commercial fusion plant should look like.

The construction of Iter’s massive tokamak started in 2013 (the project itself began in 1988) – but the facility is already way over budget (the current estimated cost is €20bn) and behind schedule. When a further delay in Iter was announced in January – it might not switch on until 2035 or so – some cynics wheeled out the old saw that fusion is perpetually just 20 years away. But such setbacks are to be expected when you consider the magnitude of what’s being attempted: to make a piece of a star on Earth.

Not all of the fusion eggs are in this one basket. The EU is planning a smaller prototype plant called Demo. Another, called Sparc, is now being built in Massachusetts in a collaboration between MIT and the private fusion company Commonwealth Fusion Systems. China, Japan and Russia have their own plans, and there are several dozen private companies worldwide with ambitious goals.

All the same, most fusion experts believe we’ll be lucky to have a prototype plant producing a net gain by 2040, and it’s unlikely that fusion energy will be going into the grid in significant amounts before 2050. When fusion start-ups announce that they’ll have a working reactor generating power within a decade, it’s a message for investors, not a realistic promise. These companies will have their part to play – not as the plucky underdogs who crack the problem but as providers of parts and expertise in the fusion industrial ecosystem. All the same, some researchers worry that over-promising could foster complacency that stymies investment in the urgently needed stopgap alternatives to fossil fuels, such as renewables and nuclear fission.

The Soviet fusion pioneer Lev Artsimovich once said that humankind would have fusion energy “when society needs it”. In one sense he was sadly mistaken: we needed it years ago, before the lethal heatwaves, the wildfires, the shrinking ice caps. But it’s not too much to hope that we will have it before we make the planet uninhabitable, and that it can eventually turn the climate crisis into a catastrophe averted. Cynicism about fusion is cheap, but the progress is undeniable, and even exciting – so long as we keep it in perspective.