The world needs abundant, clean energy. Fusion – with no CO2 emissions, no risk of meltdown and no long-lived radioactive waste – is the obvious solution and has been for decades, but it is so hard to achieve. Controlled fusion is the ideal long-term energy source, complimentary to renewables. But why has it proven so difficult?
The challenge is that fusion only happens in stars, where the huge gravitational force creates pressures and temperatures so intense that usually repulsive particles will collide and fuse. On Earth we need to create similar conditions and hold a hot electrically-charged plasma at high enough pressure for long enough for fusion reactions to occur. This is understandably tricky and the problem has occupied some of the world’s brightest minds for over half a century. Different approaches to fusion energy are being pursued – from cold fusion, which still lacks evidence and may never work, to inertial fusion, which could work, to magnetic fusion, which really does work.
The magnetic fusion approach uses strong magnetic fields to pressurize and trap the hot plasma fuel. Within magnetic fusion there are many different configurations of magnets, but the best performance, by far, has been achieved in ring-doughnut-shaped tokamak devices, the simplest shape that has no open-ended magnetic field lines. The JET tokamak at Culham Laboratory achieved 16MW of fusion power in 1997 with 24MW of input power.
However, progress since then has slowed because the successor device, ITER, reached such gargantuan proportions that it has succumbed to numerous delays. In recent years, some have been questioning the possibility of a smaller way to fusion.
Fusion is undoubtedly hard to achieve, but the difficulty of the challenge is more than matched by the value of the solution. In 2013, Lockheed Martin showed how compact fusion could meet global electricity consumption (44,000,000 GWh per year) by 2045. At present day prices of 5 cents per kWh, that would be worth $2.2 trillion per year.
Lockheed Martin aims to build a compact fusion reactor in 10 years using a cylindrical design with magnets at each end. Using a smaller design, they say, would make it easier to build up momentum and develop faster. Start-ups are also rising to the challenge – each with new, smaller solutions to the fusion problem. General Fusion in Canada, Helion Energy in the United States and others are investigating new approaches to fusion energy.
But what of the tokamak? Is there a way of reducing scale of this most studied and top-performing device? We think there is.
Within the class of tokamaks there are two choices – the conventional doughnut shape such as JET or the apple-shaped spherical tokamak, described recently by Dan Clery in Science Magazine as “the new kid on the block”.
The spherical tokamak has two big advantages: Being a squashed-up version of the tokamak it is inherently compact. Additionally, it uses the magnetic field more efficiently. Its limitation has always been the tricky engineering due to lack of space in the centre for magnets. But recently a solution has been found. The latest generation of a high temperature superconductor (HTS) is remarkably able to conduct high currents with zero resistance at temperatures well above absolute zero and in a strong magnetic field. Exceptionally high-field magnets can now be made allowing much simpler solutions to the engineering problems of magnet cooling and protection.
Earlier this year Tokamak Energy scientists published two ground-breaking papers in Nuclear Fusion. One showed for the first time that it is feasible to build a low power (~100MWe) tokamak with a high power gain. The second tackled one of the toughest of the engineering challenges of a compact spherical tokamak – the shielding of the centre.
So instead of building ever larger tokamak devices, with huge costs and long timescales, we can see a way forward by increasing the magnetic field in more compact devices. This turns the pursuit of fusion energy from a big moonshot to a series of engineering challenges: can we build a tokamak with all its magnets made from HTS? Can we get to fusion temperatures in a compact device? Can we get to fusion breakeven in a compact device? Can we get sufficiently beyond breakeven to produce electricity for the first time? And, can we go on from that to build reliable, economic, fusion power plants?
Tokamak Energy is deliberately trying to tackle a series of increasingly difficult engineering challenges as rapidly as possible. We have built and demonstrated a tokamak with all its magnets made from HTS and we are now designing the device to get to fusion temperatures. When we succeed with one challenge, we can raise the investment to tackle the next challenge. We may have some failures, but failing quickly at small scale can be a great way to learn and recover rapidly.
Tokamak Energy is able to pursue the goal of fusion energy in this particular way because of two local clusters of expertise in England’s Thames Valley: one based on the world class fusion research at Culham Laboratory; the other based on the world leading high-field superconducting magnet businesses of Oxford Instruments and Siemens Magnet Technology, who supply magnets for scientific instruments and MRI.
Fusion energy projects and start-ups around the world may pursue the goal of fusion energy in different ways by playing to their distinctive strengths. The increasing number of start-ups coming onto the scene is encouraging. A competitive race and more private investment would be good for the progress of fusion.
None can be certain of success yet, globally, we must try. All will need help from partners from many parts of the world. A concerted effort towards fusion energy is the best way to solve the pressing need to reduce greenhouse gas emissions and ensure the supply of safe, clean energy long into the future. The global impact of electricity from fusion will be huge. We must try harder to get there quicker. Thinking smaller is the key.
Full details on all of the Technology Pioneers 2015 can be found here.
Author: David Kingham is Chief Executive Officer of Tokamak Energy, a World Economic Forum Technology Pioneer.
Image: A worker watches a display showing video and a computer-rendering of a previous fusion experiment inside the JT-60 tokamak at the Japan Atomic Energy Agency’s Naka Fusion Institute in Naka, Ibaraki Prefecture north of Tokyo July 23, 2008. REUTERS/Michael Caronna