Years of scientific study of the earth’s climate, human influence on it and the impacts of a changing climate have made it clear that we have to stop using the fossil fuels that have provided the energy for the incredible technological advancement of our societies. Of course there are other, cleaner ways to make use of the energy that is ultimately provided by the Sun than using the highly concentrated chemical energy in the remains of organisms millions of years old. Wind turbines and solar panels are popular renewable alternatives, but because the energy content of the wind and Sunlight is not as concentrated as it is in fossil fuels, an incredible number of wind turbines and solar panels will be needed to supply the world’s energy needs.
Since the energy of both fossil and renewable energy sources ultimately comes from the Sun, it is interesting to look at how this distant, giant ball of plasma produces this enormous amount of energy. Our Sun was created by the gravitational collapse of the solar nebula, an enormous gaseous cloud consisting for a large part of hydrogen. During this collapse, the mass of the early Sun was increasing rapidly and so was its gravity. The huge gravitational force caused the Sun’s core to become incredibly dense and hot, until it exceeded the temperature needed for stellar nucleosynthesis: in the Sun’s case the nuclear fusion of hydrogen atoms to form helium. It is this fusion that releases enormous amounts of energy in the Sun’s core and this energy is what is preventing the Sun from collapsing under its own gravity.
Could humans, instead of using the Sun’s energy, find a way to directly get energy from a fusion process here on earth? Of course we already have nuclear power, but this is energy from a controlled nuclear fission1 process that mostly uses the relatively rare and heavy element uranium. There is a limited supply of uranium available on Earth and only a small part resides in conventional high-grade ores. Apart from issues with the main resource, nuclear waste is a serious problem: radioactive contamination is dangerous to all life and so the radioactive waste products of nuclear fission have to be stored safely for very long times until all radioactive material has decayed to stable daughter elements.
Nuclear fusion is much more difficult to do here on Earth, because star-like conditions, meaning a plasma of 100 million K, have to be recreated in order for fusion to be able to take place. This is possible and it has already been seen in hydrogen bombs, which are nuclear weapons that use the energy of a nuclear fission reaction to start a nuclear fusion reaction. Successful nuclear fusion in a bomb is one thing, but creating an ongoing, safe and energy-yielding fusion reaction in the lab has not been done yet. It proved to be difficult to confine this plasma: in stars this happens because of gravity, but on earth this has to be done in a different way, for example with magnetic confinement. Also, you can probably imagine that it takes a lot of energy to heat something up to 100 million K and to date there has not been an experiment in which the energy yield of fusion exceeded the energy needed to initiate the reaction. However, nuclear fusion for energy production is still a very active area of research2 and experts believe that a successful nuclear fusion reactor will be on the grid in the coming decades. Just recently, a collaborative initiative between MIT and a private company claims that it will provide electricity from nuclear fusion within 15 years3.
It is clear why countries and organizations are making huge investments in nuclear fusion research: according to Ongena (2016) the resources needed for fusion can be obtained in a cheap way, it is a nearly inexhaustible source of energy, there is no carbon involved in the process, a fusion reactor is expected to be much safer than a fission reactor and no long-term storage of nuclear waste is involved. This makes nuclear fusion a very promising option in the energy transition. It could for example complement intermittent renewables like wind and solar energy, so that energy availability is much more stable and less storage capacity is needed, addressing currently important concerns of a renewable based power grid. In my opinion, we should keep investing money in nuclear fusion research so that one day we might have plenty of clean and safe fusion energy available. However, we should not wait around and do nothing or even use the development of nuclear fusion power as an excuse to reduce our current efforts on reducing fossil fuel emission, but we should keep investing in other renewables as well.
1. You may wonder why energy can be released from fission as well as fusion processes, while these are reverse reactions (fusion means adding protons and neutrons to the nucleus, while fission is removal of protons and neutrons). This has to to with the nuclear binding energy curve:
The general shape of the curve is a positive slope for elements lighter than Fe56(iron) and a slight negative slope for heavier elements. This means that fusion of elements releases energy for elements lighter than Fe56(exothermic), while energy is needed for fusion of elements heavier than iron (endothermic). Conversely, fission of elements lighter than iron takes up energy, while fission of elements heavier than iron releases energy. This is the reason that the very heavy uranium is used to get energy from fission in nuclear reactors, while nuclear fusion would involve light elements, most likely hydrogen.
2. If you’re really interested in the research on this topic, since 2012 there has actually been a Master’s programme at the Eindhoven University of Technology called ‘Science and Technology of Nuclear Fusion’.
3. It should be noted that scientists have claimed that they are close to nuclear fusion energy for over 50 years. It remains to be seen whether this initiative will reinforce the stereotype of fusion scientists always saying that they are close to fusion power, but never actually getting there, or that it will finally be a success.
Gabriel S, Baschwitz A, Mathonnière G, Fizaine F, Eleouet T. 2013. Building future nuclear power fleets: The available uranium resources constraint. Resources Policy. 38(4):458-469.
Kirk A. 2015. Nuclear fusion: Bringing a star down to Earth. Contemporary Physics. 1-18.
Ongena J. 2016. Nuclear fusion and its large potential for the future world energy supply. Nukleonika. 61(4):425-432.
Richter J. 2017. Energopolitics and nuclear waste: Containing the threat of radioactivity. Energy Research & Social Science. 30:61-70.