Nuclear fusion is the most basic form of energy in the universe. It is what powers the sun (pictured) and all of the stars. It is produced by a nuclear reaction in which two atoms of the same lightweight element, usually an isotope of hydrogen, combine into a single molecule of helium, the next heavier element on the periodic table.
Humans have successfully produced an uncontrolled fusion reaction to make the hydrogen bomb, in which all the tremendous energy of the reaction is released at once in a highly destructive manner. If the same amount of energy could be released gradually, in a controlled fusion reaction, which is what occurs in the sun, this could become the ultimate form of energy on Earth.
But creating a controlled fusion reaction has proven very difficult so far. Because the two hydrogen atoms have the same charge, they will electrically repel each other. The tremendous heat of the sun, which is somewhere in the neighborhood of 12 million degrees C, accelerates them to the point where their momentum overcomes the electric repulsion. Producing these kinds of temperatures in what is essentially a synthetic sun is a great engineering challenge. The elements are heated until they reach a plasma state. No material could possibly withstand such heat without melting, which is why the reacting elements must be suspended without touching the walls in the vessel. This can be done with either gravity, inertia, or magnetism, all of which are very challenging to create and control The resulting continuous reaction, known as a thermonuclear reaction, could then be used to create steam in a boiler which could then generate electricity using a conventional turbine.
The experimental reactors that are in use today all use deuterium and tritium as the main elements. Deuterium can be extracted from sea water. Tritium can be made from deuterium in contact with lithium.
Fusion research began in the 1950’s, in England. In 1968 the Russians created the first reaction in their Tokomak reactor, which utilized magnetic confinement. In 1991, the Joint European Torus (JET) reactor produced 1.7 MW. Two years later, the US-based Tokomak fusion test reactors (TFTR) produced 10 MW. Today there are some 25 experimental reactors in existence. The most ambitious is the International Thermonuclear Experimental Reactor (ITER) currently under construction in France, which hopes to achieve 500 MW of output for approximately 1000 seconds. The earliest projected date for a commercial facility is not expected until around 2050.
If room temperature, or cold fusion could be developed, it would be much easier to implement and control. A pair of researchers, Pons and Fleischman from the US and England claimed to have demonstrated a cold fusion reaction in 1989, but the process could not be independently verified. Today, an Italian scientist, Andrea Rossi, claims to have a successfully created cold fusion system, but his results, which appear to contradict known science, have also not yet been independently verified.
No one knows when a successful continuous controlled fusion reaction can be achieved or even if it is ultimately possible. Billions of dollars have been and continue to be invested in research since the potential benefit is considered so great.
Pros of nuclear fusion
- Clean energy. No greenhouse gases.
- Virtually limitless fuel available. (The deuterium can be distilled from seawater and the tritium can be “bred” in the reactor.)
- No chain reaction. Easier to control or stop than fission.
- Little or no nuclear waste. Core remains radioactive for only 100 years. Possibly radioactive structural elements.
- Very low fuel cost
Cons of nuclear fusion
- Unproven at anything resembling commercial scale.
- No full scale production expected till at least 2050
- Commercial power plants would be extremely expensive to build
- Requires extremely high temperatures. Difficult to contain
- Could produce a net negative amount of energy
- If cold fusion could be achieved, it would be much easier to implement.
- The billions in research funding could be spent on renewables instead
- Would remove any incentive for restraint in the use of energy.
In many ways, fusion power seems like the perfect energy source. It’s clean, it’s inexpensive, and it uses seawater as its fuel source. It’s the Holy Grail, it’s the pot of gold at the end of the energy rainbow, and it has no appreciable side effects, except for one: modern civilization on steroids.
If commercial scale fusion plants were to become a reality, we would have an unlimited, nearly free, clean source of energy. And if limited energy supply and climate change were our only problems, or, should I say the only geophysical constraints imposing themselves on our way of life, then that would be the happy ending to the story.
But here is where we need to step back and look at the larger picture. We need to look at the very question of energy consumption in the larger context of our planetary ecosystem and our survival within it. Scientists at the Stockholm Resilience Centre, have identified, not one, but nine planetary boundaries that define the envelope within which we must conduct our affairs if we are to avoid destroying our very source of sustenance. In addition to climate change, there is also biological diversity, nitrogen and phosphorus consumption and release, ocean acidification, stratospheric ozone, land use change, freshwater availability, aerosol loading, and chemical pollution.
According to the analyses these folks have conducted, we need to respect all of these boundaries in order to maintain the comfortable living conditions we enjoy now. Unfortunately, we may have already crossed the first three.
We must confront this reality, as we engage the question of how to manage our energy future, because energy is so inextricably tied to our impact on all of these. If we didn’t have access to the tremendous amount of energy we expend every day, we wouldn’t be anywhere near any of these boundaries. Energy consumption has always gone hand and hand with material consumption, resource depletion, and environmental pollution. While it’s true that fusion power would not produce these things directly, it would enable them to continue unabated, giving mankind unprecedented power to do harm as well as good.
If we are going to move to a more sustainable, lower impact way of living on this planet, we need to do a lot more than substitute a clean and renewable source of energy for the ones we are using now.
Most of the projections for a renewable energy future involve a healthy dose of conservation as well as efficiency. That implies some level of re-examination of our current way of life, in everything from how much we consume to how we lay out our cities, how we move around, and how we feed ourselves, just to mention a few areas.
If someone were to walk up and hand us the keys to nuclear fusion power tomorrow, I’m not at all sure that we would have the wisdom or the maturity to reign in our consumption, once we no longer needed to. Yet if we don’t we are likely to put increased pressure on a number of these planetary boundaries.
There is one further and perhaps more immediate concern about the fusion scenario. It is not expected to be commercially available until somewhere around 2050. If you believe the projections on climate change, we pretty much need to have our energy house in order by then, with a dramatically lower carbon footprint that needs to begin dropping yesterday. The DOE has forecast that the US can meet 80% of its electricity demand from renewables by that time using existing technology while Denmark will be fulfilling 100% of its total energy needs with renewables by then.
Given that the fusion approach, will not, failing any miraculous breakthroughs, be ready by the time we need it, which is very soon if not now, it could be argued that it makes more sense to spend those billions of research dollars on something that will be.