Thursday, March 15, 2012

The Future is Fusion

So I'm back from my vacation. Hooray! Vacations can be fun, but after a while you just want to get back home. Anyway, this next piece is somewhat more technical than my previous pieces, but I hope that you'll enjoy it nonetheless.

Energy Today

We are currently experiencing an energy crisis. For over 150 years now we have been extracting energy from the earth in the form of oil and gas. For a long time this was seen as a good thing -- these fuels were the energy backbone that helped to build the modern world. In fact, more than half of all energy production in the United States is derived from oil and gas. However, oil and gas are very polluting forms of energy. Combustion of these resources releases a slew of harmful substances that include mercury and sulfur dioxide, as well as vast amounts of carbon dioxide.

Even if one were to ignore the health and environmental effects of burning fossil fuels for energy, it’s hard to ignore the fact that we’re running out. After a century and a half of extraction, the world’s oil and gas reserves are vastly depleted. As the remaining stocks decline even further, oil and gas prices will continue to rise. This in turn causes those products that are dependent on oil and gas to rise in price.

This is where alternative energy comes into play. For several decades now, solar, wind, wave, and geothermal power as well as biofuel, hydroelectric power, and even people power have been an ever growing part of the energy mix that powers our world. All these technologies are wonderful in their own right, and they are certainly helping to reduce our dependence on fossil fuels, but I feel that they are only partial solutions and intermediary technologies on the way to something even better; something that will permanently and completely solve our energy crisis: Fusion power.

Fusion Power

Fusion power, as you might know, is caused when atomic nuclei fuse together, simultaneously creating a heavier nucleus and releasing enormous quantities of energy. A fusion power plant would be able to create these reactions and harness that energy to power our planet.

Fully functional fusion plants generate no pollution and exceedingly small amounts of CO2 during operation, and are almost completely environmentally benign. A fusion plant requires only 3 things to operate; deuterium, (an isotope of hydrogen) which is readily available and extractable from water; lithium, (also readily available in sea water or the ground) and tritium (another isotope of hydrogen) which can actually be created as a byproduct of the fusion process, thereby allowing it to be made on site.

Fusion plants are also significantly more efficient at creating usable energy than any other method currently available. A 1,000-megawatt fusion power plant would consume around 100 kilograms of deuterium and three tons of lithium in a year whilst generating 7 billion kilowatt-hours. To generate the same amount of electricity, a coal-fired power plant would need around 1.5 million tons of coal.

So we’ve determined that fusion is both cleaner and more efficient than other available methods. But what about safety? Isn’t there a radiation risk? After last years Fukushima disaster, many people are wary of anything nuclear. Have no fear. Fusion plants cannot meltdown... ever. By their very nature, such an event is entirely impossible.

To better explain the veracity of this claim, a brief (but by no means complete) explanation of how a fusion reactor works is in order.

How a Fusion Reactor Works

To create fusion (and electricity) in a fusion reactor several precise steps must be undertaken. First, hydrogen atoms must be heated up until they turn into superheated plasma. Then, through the use of a toroidal (donut shaped) magnetic field, the plasma is compressed to the point of fusion. The fusion process releases super-energetic neutrons (which are magnetically neutral and therefore are not contained by the magnetic field) that shoot out from the fusing plasma and are absorbed by what is known as a lithium blanket that surrounds the whole process. The absorption of these neutrons heats the lithium blanket. That heat is then transferred to a heat exchanger to make steam. The steam in turn drives electrical turbines to produce electricity.

As I mentioned, a magnetic field is required to compress the superheated plasma into fusing. The reason that a magnetic field is used rather than some other method is because the plasma created is so hot that if it came into contact with anything corporeal, it would instantly vaporize it. But what if the magnetic field failed and the plasma escaped? The magnetic field is created by superconducting magnets that line the walls of the fusion chamber. If the plasma were to somehow escape the confines of the magnetic field, it would instantly vaporize these magnets. Without the magnets, the magnetic field would immediately destabilize, and without the presence of the magnetic field, the compression of the plasma would cease, instantly halting the fusion reaction. This is why a runaway fusion reaction is impossible.

So now we know that not only is fusion cleaner and more efficient, but it’s completely safe as well. That begs the question: where are all the fusion plants?

What Still Needs to be Done

The simple answer is that the technology is not quite there yet. Thus far, every experimental fusion reactor ever built has been unable to attain net usable power. In other words, creating the fusion reaction has always required the input of more energy than the reaction itself creates. Another major problem has been sustainability of the reaction. The longest sustained fusion reaction on record only lasted for around five seconds before the process collapsed.

But things are changing.

Construction is currently underway to build ITER, an internationally funded and operated nuclear fusion research project, which when completed around 2018-2019, will be the world’s largest and most advanced experimental fusion reactor. It is expected to produce 500 megawatts of output power from only 50 megawatts of input power, or ten times the amount of energy put in. This would make it the first fusion reactor to ever achieve net usable power. And while the current record for a sustained fusion reaction is 5 seconds, ITER it is hoped, will be able to sustain a reaction for 500 seconds.

But it doesn’t stop there, either. The successor to ITER, DEMO, is expected to produce 25 times as much power as it consumes, and be able to sustain a reaction indefinitely. And if ITER and DEMO are successful, then the next step is to build commercial fusion reactors. If all goes as planned, these reactors should start producing electricity by the 2040s.

As things stand today, commercial fusion reactors are still around 30 years away. It might seem like a long wait, but mark it on your calendar anyway. For it marks the point at which the world will finally become free from its dependence on fossil fuels.

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