Renewable energy research is underway to solve the problem of carbon dioxide emissions from fossil fuel power generation, one of which is nuclear fusion energy generated in tokamaks using superconductors. Superconductors have zero resistance at extremely low temperatures, allowing strong electricity to flow through them, which is essential for creating artificial suns. Future advances in superconductor technology could provide green energy without polluting the environment.
Fossil fuel power generation has been criticized for its excessive emission of carbon dioxide, which has caused the greenhouse effect and accelerated global warming. As a solution, renewable energy sources that do not pollute the environment are being actively researched, and one of them is nuclear fusion energy. Nuclear fusion is when two or more atomic nuclei come together to create a new nucleus. This process releases a large amount of energy due to the loss of mass, which is called ‘fusion energy’.
The sun is a prime example of a source that utilizes this process to produce enormous amounts of energy. The sun uses high temperatures and high pressures to create energy by fusing hydrogen nuclei together. This energy is so enormous that it is enough to power photosynthesis in plants and keep many living things warm on Earth. This natural wonder has inspired humans, and we have worked hard to replicate this same energy source on Earth.
The use of nuclear fusion energy requires conditions of extremely high temperature and pressure. To fulfill these conditions, specialized vessels and technologies are needed. It’s easy to think of it as a vessel for an “artificial sun.” So scientists have developed a new type of vessel called a tokamak.
The tokamak looks like a donut at first glance. Inside, hydrogen atoms undergo a nuclear fusion reaction to create an artificial sun. How to maintain the conditions of ultra-high temperature and ultra-high pressure that create it is hidden in its donut shape. The tokamak has spiral-shaped wires that surround the doughnut shape, and when electricity is applied to those wires, a magnetic field is formed inside the spiral – the shape of the tokamak – which raises the temperature and pressure inside the tokamak and traps the artificial sun inside the magnetic field. However, it’s not possible to create ultra-high temperatures and pressures using ordinary wires, such as simple copper wire, because the resistance of the wire itself and the heat it generates would make it impossible for the tokamak to work if it were to flow an excessive amount of electricity. To compensate for this, we need to use wires made of a special material that has no resistance and therefore generates no heat. This is the key to the tokamak.
Do materials with no resistance exist? Yes, they do exist. Of course, only under special conditions, but there are materials that have zero resistance: “superconductors”. A superconductor is a material whose resistance drops to zero at some point at a very low temperature, such as cryogenic temperatures. In order to use superconducting wires, Tokamak flows liquid helium, which is minus 269 degrees Celsius, around the wires. The purpose of this liquid helium is to keep the temperature of the superconductor at cryogenic temperatures.
So why does a superconductor have zero resistance at cryogenic temperatures? The reason is that when the temperature drops below a certain point, the electrons pair up and exhibit a behavior not seen at room temperature. That point is called the “critical temperature” and the pairs are called “Cooper pairs.” Electrically, when a negatively charged electron passes through a lattice of positively charged electrons, the electrostatic attraction causes the lattice to tilt slightly in the direction of the electron’s path. The electron that follows will be more affected by the positive charge than the electron that passed before it. In this process, two electrons form a pair.
When two electrons form a Cooper pair and behave like a single particle, they become “oriented”. Previously, individual electrons were “symmetric” rather than “directional” because they all moved in different directions, but after forming a Cooper pair, all the Cooper pairs have the property of wanting to flow in one direction, so all the electrons behave as if they were a single mass. These same oriented Cooper pairs will continue to flow even if they encounter any obstacles, meaning that electrical resistance is completely eliminated. For this reason, at temperatures lower than a critical temperature, resistance is eliminated, allowing stronger electricity to flow.
So far, we have seen how superconductors are a key element in nuclear fusion energy. In a few decades, when superconductors with higher critical temperatures are developed and superconductor technology becomes more advanced, nuclear fusion energy will be commercialized, and people around the world will be able to enjoy the benefits of clean, renewable energy without polluting the environment. Several ongoing research projects are also playing an important role in realizing this vision. These technological advances will pave the way for a better environment and sustainable energy for future generations.
