The energy we use comes from the sun, which generates energy through nuclear fusion. Attempts to harness nuclear fusion on Earth are underway, and tokamak devices are exploring the possibility of providing unlimited energy in the future.
Where does the energy we use come from? Earth gets energy from sunlight to circulate water, store it as heat in the ground, and enable plants to photosynthesize. These processes are essential to life on Earth and make it possible for all living things to survive. Solar energy also plays an important role in regulating Earth’s weather and climate. Thanks to these complex and sophisticated natural systems, we live in a stable environment. And we use the energy stored in these different forms to sustain life, make things, and generate electricity. In other words, the energy we use comes from the sun. But how does the sun get its energy? The answer is: nuclear fusion.
Nuclear fusion is a process in which lighter atomic nuclei combine and turn into heavier ones. The principle of how energy is obtained from nuclear fusion is the mass-energy equivalence principle discovered by Einstein. In simple terms, the mass-energy equivalence principle states that mass can be converted into energy, which is expressed in the formula E=mc². Here, E is energy, m is mass, and c is the speed of light, which is 300,000 km/s, which is a very large value. This means that a small change in mass results in a large change in energy. Atoms with an atomic number of 26 or less release energy when they fuse, reducing their overall mass, and in the sun, hydrogen with an atomic number of 1 fuses to produce energy. But can we harness this amazing energy directly?
Nuclear fusion requires high pressure and temperature to occur. Coulomb’s law states that the magnitude of the force acting between two charges is inversely proportional to the square of the distance between them. Since atomic nuclei are positively charged, the closer two nuclei come to fuse, the greater the force of attraction between them. High pressure and temperature are needed to get enough energy to overcome this force. The Sun is so large and heavy that the pressure exerted on its core by gravity is so high that nuclear fusion can occur at temperatures as low as 15.7 million degrees Celsius at the Sun’s center. Thanks to this enormous pressure, the Sun is able to stably sustain nuclear fusion, which in turn provides a steady supply of energy to Earth. On Earth, however, we don’t have the same gravity, and we don’t have the materials to withstand the pressure of the sun, so we can’t fuse under the same conditions as the sun. However, if we raise the temperature high enough to overcome the low pressure, nuclear fusion can occur. On Earth, we need to maintain an environment of more than 100 million degrees Celsius for fusion power generation. But even carbon, the element with the highest melting point, can’t stay solid at just 4,000 degrees Celsius. Is there a container that can hold a substance at 100 million degrees?
To solve this problem, several laboratories, including KSTAR in South Korea and ITER in Europe, use a device called a tokamak. TOKAMAK translates to “toroidal container with a magnetic coil”. A magnetic coil literally means a magnetic coil, and a toroid is a type of electromagnet. An electromagnet is a magnet that utilizes the law that when an electric current flows through a wire, it creates a magnetic field around it, and unlike traditional permanent magnets, the strength of the magnet can be adjusted by adjusting the strength of the current. A typical example of an electromagnet is a solenoid, which is an electromagnet made by winding a wire around a highly magnetized material, such as iron, like a molten iron. A toroid is a solenoid bent into a donut shape. When current is passed through the toroid, a magnetic field is generated inside the toroid, which the tokamak uses to control the ultra-high temperature material inside. The reason why the magnetic field can control the ultra-high temperature material is because the material is a plasma. When a gas is continuously heated to increase its temperature, the positively charged atomic nuclei and negatively charged electrons are separated and become plasma, a charged gas. Since charged materials can be controlled by magnetic fields, tokamaks can trap materials at extremely high temperatures by controlling the plasma so that it does not touch the walls of the container.
The raw material for fusion power can be obtained from seawater. A small amount of deuterium in 1 liter of seawater can produce the same amount of energy as burning 300 liters of gasoline. Seawater covers about 70% of the Earth’s surface, and harnessing this resource opens up the possibility of fundamentally solving the energy problems facing humanity. In addition, the power generation process produces virtually no greenhouse gases, and unlike conventional nuclear power plants that use nuclear fission, there is no risk of radioactive leakage or explosion in the event of an accident. For these reasons, fusion power is considered the “ultimate energy source of the future”.
However, fusion power is still a long way off. The main reason is that it’s very difficult to control the plasma. Because plasma is a charged, highly energetic fluid, its complex nature makes its motion very complicated. This makes it very difficult to predict and control its motion. The motion of plasma sometimes exhibits unexpected instabilities that puzzle researchers. To solve this problem, experts from various fields are collaborating to conduct research and experiments around the world. In Korea, we are also working on a technology development roadmap with the goal of commercializing nuclear fusion in the 2040s. Through such international cooperation and research, we are gradually increasing the feasibility of nuclear fusion, which gives us great hope for solving future energy problems.
Nuclear fusion power generation is expected to be feasible in the near future. And tokamak is considered to be a promising technology for realizing nuclear fusion power. If fusion power generation using tokamaks is commercialized, countries around the world will have a small sun for their citizens in a donut-shaped magnet. We can look forward to a future energy era where we don’t have to worry about resource depletion and environmental destruction.
