Our planet’s future energy production and its harmful waste by-products have finally reached the center of public attention. “Fridays for Future” demonstrations have gained major traction, the governing coalition in Germany has committed to a multi-billion euro climate package, and CEOs of multinational corporations have become well-meaning climate protectors.
It is precisely at this time, without this receiving much public attention, that scientists are making progress in an area that could solve the problems of global energy supply once and for all: the peaceful use of nuclear fusion. This is about nothing less than finally fulfilling the dream of unlimited, clean and safe energy from the thermonuclear fusion of atom nuclei, the very same process that supplies our sun and stars with seemingly endless amounts of energy.
The history of nuclear fusion research is almost a century old. Since the 1930s, physicists have known that under very high pressure and temperature, hydrogen nuclei fuse into helium nuclei and that it is this mechanism (as well as the fusion of higher nuclei) that enables the sun to generate its energy. The energies released via fusion are much higher than via fission (in which heavy atomic nuclei are split), which nuclear power plants have used for more than 60 years. The reason for the energy gain is that the fusion of light atomic nuclei leads to a loss of a small amount of mass. This mass defect manifests itself directly in the kinetic energy of the particles produced. According to Einstein’s famous formula E=mc², even with the low amounts of lost mass this energy is enormous because this mass (m) is multiplied by the square of the speed of light (c²).
Back in the early 1940s, the American researcher (and later father of the hydrogen bomb) Edward Teller and the Italian Enrico Fermi (who was the first to perform controlled nuclear fission) developed the ideas of power generation on the basis of controlled nuclear fusion. Their basic concept still holds for nuclear fusion researchers today: a deuterium-tritium plasma (deuterium and tritium are isotopes of hydrogen, i.e., a proton is joined by one, respectively two neutrons) is heated to several million degrees in a kind of microwave and then enclosed and controlled by means of a magnetic field (such a plasma consists of charged particles and can therefore be controlled by such fields). As of about 100 million degrees – the precise ignition temperature depends on the particle density of the plasma – the mixture ignites and releases the fusion energy.
It is difficult not to fall into ecstatic excitement in view of the practically unlimited possibilities of nuclear fusion. The energy released is safe, carbon-free and the required initial materials are abundantly available. The primary fuel, hydrogen isotopes, can be found in normal ocean water. One kilogram of the deuterium-tritium mix is enough to supply an entire city with energy for a very long time. A functioning reactor would only need five kilograms of hydrogen to produce the energy equivalent of 18,750 tons of coal, 56,000 barrels of oil or the amount of energy 755 hectares of solar collectors produce in one year.
Unfortunately, a 100-million-degree hot mixture of hydrogen nuclei is so difficult to control that a well-known joke among physicists is that nuclear fusion is the most promising technology of the future…and will remain so forever. The reason is that the ultra-hot plasma must be kept under control, since it immediately cools down upon contact with the “outer world” (e.g., the container walls), which interrupts the fusion instantly.
To this end, researchers and engineers are developing enormous magnetic fields in order to contain such a plasma, which consists of charged particles. But to maintain these fields with high performance and at the same time great precision, is an incredibly difficult technological challenge that top scientists all over the world have been working on for decades. So far, they have done so with only moderate success and at very high costs. The total projected costs of the main thermonuclear experiment today stand at over 20 billion euros and will go as high as 60 billion euros according to some experts. This is already the most expensive experiment in the history of science. The ITER experimental reactor is being financed by an international consortium and built in the French town of Cadarache. It is expected to produce its first results from 2030 onwards. However, a net electricity output is not expected before 2040, at the earliest.
Significant challenges must be overcome. The deuterium-tritium fusion reaction produces neutrons of very high energy. These neutrons (which cannot be controlled by the magnetic field) collide in large numbers at very high speeds with the material of the reactor’s container. After only one or two years, the damaged container must be replaced, at significant cost. Moreover, the neutron bombardment creates radioactive waste, leading to a disposal challenge. A ‘clean’ boron-proton reaction is the alternative, but it requires about 30 times higher plasma temperatures to ignite.
A number of private companies are also engaged in nuclear fusion research, with many taking different routes than the scientists at ITER. Aided by alternative and smaller reactor technologies, these companies are trying to generate electricity from fusion within the next few years. Some, backed by big investors, have recently made considerable progress, much of it out of public view. Leading these efforts is a company called TAE Technologies, based in Irvine, California. Its publicly announced funding exceeds $750 million, and known backers include venture capital firms New Enterprise Associates and Venrock, the UK’s Wellcome Trust, several sovereign funds, Alphabet (Google) and other high-tech investors.
The path towards a functioning fusion reactor does not lead via completely unknown physics. Rather, it is primarily a question of good engineering and the understanding of the complex thermodynamic and magnetohydrodynamic properties of high temperature plasmas. And it is precisely here where the private companies have made significant, perhaps even decisive, progress in the last few years.
The science and engineering may seem daunting, particularly to those not intimately versed in the field. The key is to provide, at reasonable cost and efficiency, a stable environment in which fusion can be controlled without creating a by-product of radioactive waste. Private sector actors are pursuing different routes to achieve this aim, exploring trade-offs between fusion length and temperature and working with alternative technologies, such as lasers to generate the required temperatures. This work could potentially unlock limitless energy, in a commercially viable manner, within one generation. Private sector capital flowing into this space is a clear sign that such dreams are becoming closer to reality.
Commercially available fusion technology, if feasible, would drive a paradigm shift in society. Energy produced on earth, as it is in the sun, would provide humankind with access to the most efficient, safest and most environmentally friendly form of energy that nature offers. It would represent a leap forward in civilization itself, beyond even the invention of the steam engine that provided the energy for turning human society upside down 250 years ago.
When humanity masters nuclear fusion, we will have taken our most significant technological leap since our ancient ancestors discovered fire.