After Einstein’s work showing that matter and energy are interchangeable, we can say now that the universe is simply a great amount of energy in different states. Rational beings are some kind of aggregated energy in a certain form, a form that tries to preserve its state along time. Human activities are driven by the natural need to get energy in order to preserve the human life, to develop it and to multiply it. Civilizations are the result of the change the natural impulse of searching for food (the energy source for our bodies) by a planned way to get it. It is not an exaggeration saying that energy is the only important thing in our human lives because energy is, basically, the only thing existing in the universe.
Modern civilizations are very dependent from energy sources. A modern society cannot be preserved without large energy sources. What makes a society more advanced is the capability to understand, to get and to use larger energy sources. We can think now, that what defined our modern societies in the twentieth century is the result of mankind getting energy from the atom. We are taking advantage of the division of heavy atoms in order to get a huge amount of energy. Nuclear power stations are without any doubt the reason for the social development of the occidental societies. The access to a huge energy source provides independence and security, and avoids the need of searching for large energetic resources in other countries. Although European societies have been and are very dependent from oil, their capability to move to another sources much more efficient than fossil combustibles put them in a good negotiation position with other countries.
The twenty first century will be defined by a different energy source. Although from the energetic viewpoint nuclear fission is very efficient (it produces a huge amount of energy from a little amount of combustible), nuclear fission has many problems that are not easy to be overcome, related to safety assurance, residual waste, and so on. Nowadays, energy industry is focused in getting energy from renewable sources; however, this is not a great technological advance. The concept of renewable sources is mostly the extraction of energy from the kinetic energy of the molecules in a fluid through a mechanical device. Conceptually, there is not a significant difference between the extraction of energy from the atmosphere with a wind turbine in order to feed an electrical mill that turns the electricity into mechanical work than the same process done by “a giant of Don Quixote” that turns directly the kinetic energy of the molecules in the atmosphere into mechanical work of the mill. The former one is more complex than the latter one but the mechanical work proceeds from the same energy.
The advances in energy technology have been driven by the increasing demand of energy in the modern societies. Human activities require more energy and the search for new energy sources more powerful has been common in the recent decades. Nuclear power is our last achievement; however, the game is not over.
In the previous century, science has produced two spectacular advances. The first one is Einstein’s relativity that shows a similar nature between space and time, and between matter and energy, and the second one is quantic mechanics, that shows the quantum and oscillatory nature of matter. Both advances have driven us towards a better comprehension of the universe and its energetic processes that we can try to simulate in order to take advantage of huge amount of energy.
All of the energy that we can use for our human purposes proceeds from the Sun. Without the energy of Sun it would be impossible to have any energy source on the surface of Earth like wind or water. Speaking strictly, there is not any renewable energy because even the Sun will burn out totally in a certain time. Of course, the most probable scenario is that there will not be any human being on Earth in that time.
If Sun is the primary energy source, and our terrestrial sources proceed from it, we can think that the most efficient way to get huge amount of energy should be the replication of the energetic processes in the Sun.
Astronomers have found that the energy emitted by the Sun and other stars is produced by nuclear reactions. However these kinds of reactions are fusion reactions instead of fission reactions. In a fission reaction the nucleus of a large atom is divided in several more little ones, however in a fusion reaction two nuclei of little atoms are joined to produce a larger one. The energy liberated is due to the creation of a link supported by the strong nuclear force. This kind of force acts a very tiny distances, and in order to produce the new link it is necessary to overcome the electrical repulsion due to the electric charge of the two nuclei that acts at larger distances.
Fusion reactions require a very high temperature in order to take place. On the Earth it is very difficult to create the required conditions of pressure and temperature to produce that kind of nuclear reactions in a continuous way. The lower the required temperature is, the higher our capability to produce it is. Although astronomers have found that in the universe nuclear fusion reaction that produce element until the atomic number of iron (Fe) liberating energy are common, the reaction that requires a lower temperature is the reaction that produces nuclei of helium (He) from two atoms of hydrogen (H).
Hydrogen exists in three different forms or isotopes: protium (H), deuterium (D) and tritium (T). With zero, one and two neutrons joined to a single proton.
The reaction that is produced at lower temperature is:
D + T -> 4He + n + 17.3 MeV
The other interesting reaction is between two nuclei of deuterium:
D + D -> T + H + 4 MeV
-> 3He + n + 3.5 MeV
These two reactions are equally probable.
Tritium is radioactive with a half-life of around 12 years, however deuterium is stable. Deuterium can be found in nature, because a significant percentage of Hydrogen in nature has that form in a natural way. It can be got from the water of sea at huge amounts that makes it practically inexhaustible, but tritium should be produced from another nuclear reaction. In general it can be got from Lithium (Li). Lithium exists on Earth at large quantities, it is estimated that the current (known) reserves of lithium could satisfy the current needs of energy during thousands of years through this kind of reactions.
Although a fusion reactor produces radioactive materials like tritium, its half-life is much shorter than, for instance, the residual plutonium of some kind of fission reactors, making it less dangerous and much more manageable.
The fusion energy could be the answer to the next challenges of mankind in the near future. One of the applications of this kind of energy can be space travel. A rocket powered by nuclear fusion can produce an impulse hundreds times the impulse of a chemical rocket. This fact can make easier any future interplanetary mission.
Fusion reactors are now in time of research and development. International community is developing a fusion reactor known as ITER that is only an experiment that could provide knowledge to build in the future demonstration reactors that could supply energy in an industrial way.
The construction of a fusion reactor is a great scientific and engineering challenge, because new advanced technologies of confinement supporting very high pressures and temperatures are required. Gravitational confinement is only possible in the stars (it happens in those ones known as brown dwarfs). The ITER follows the tokamak concept that is a design for magnetic confinement.
The advantages of fusion energy are enough in order to take it seriously into account as an important driver of scientific and technological development in the future years. The applications of a huge energy source can be unimaginable. Many people change erroneously technology by application. In press, many people consider facebook or twitter as modern technologies although they are simply applications; however, the technologies are the computers, the programming languages, the physical communication network, and, of course, the power plants generating energy and feeding them. We should forget never that, in fact, the entire universe, even us, is actually energy.
Other energy sources as those one known as renewable has got a long path yet, however, the path of fusion energy can be longer due to we are in the beginning yet, and future applications are not even imagined.