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Saturday, July 26, 2008

Who ate all the oil? (or The Artificial Sun)

I wrote the following back in 2006...It probably wasn't overly prophetic back then which emphasises all the more how long we have been faced with what we are faced with now.


As mankind traverses its way through a field of much uncertainty, there is no area of greater concern than that of finding a renewable source of energy. For centuries, we have been relying more and more heavily on the crutch that is fossil fuel. Like an elderly man leans more and more on his nightstand each morning just to get him out of bed, we too have come to the stage where we simply cannot carry out our daily lives without fossil fuels. They quite literally are the power behind our very existence. And just like that elderly man realises that one day, that nightstand simply won’t be able to support him anymore, we have come to the dawning of the inevitable – fossil fuel will not last much longer.

You may well be thinking that this all sounds very ominous and may well be quite a headache for billions of people. And you may well be right. Thinking about it logically, it would seem that we have three options: Our first option is that we immediately resign ourselves to literally reversing our style of living to that of a couple of hundred years ago where people got around under their own steam (or the steam of their donkey) and conserve what little fossil fuel is left so that it can be displayed in museums for generations to come so that our grandchildren may gaze in awe and wonder at these lumps of “coal?”. The second option is that we continue as we are, ignoring the inevitable until one day, we go to fill up our car but to find the garage is all out. The garage calls it’s supplier but to find that its supplier is all out, the garage’s supplier calls some guy in a hot country far away who, to the misfortune of humanity, realises that his supplier (the earth) is also all out. Now, admittedly the first of these options holds a certain Amish charm but all in all, these options present extremely limited opportunities to ‘advance’ as mankind defines the term. And that is where the third option comes in.

The third option is to find an alternative that can realistically fuel our insatiable appetite for energy. Now this sounds quite difficult to achieve and it most definitely is but in China, this is exactly what they are doing with the aid of superconducting technology. This is an area that has not quite come out of the blue. China has already built a similar device in the early 1990’s [1] in partnership with Russia. The device that is currently being built is a full superconducting experimental Tokamak fusion device, which aims to generate infinite, clean nuclear-fusion-based energy according to [2]. (The Tokamak takes its name from a Russian snack which has the same toroidal donut shape as the fusion device.)

The project is called EAST (experimental advanced superconducting Tokamak) and will require an investment of nearly 300 million Yuan. This sounds like quite a substantial amount of money but is only about one fifteenth of the cost of similar devices being developed in the other parts of the world. It is believed that deuterium extracted from the sea can be used in a deuterium-tritium fusion reaction under huge temperature of 100 million degrees Celsius. After this nuclear fusion has taken place, the deuterium extracted from one litre of sea water will produce energy equivalent to 300 litres of petrol. It is no surprise that a device that can withstand these kinds of temperatures will be no less than an ‘artificial sun’. Once it is also able to control a deuterium-tritium fusion reaction it will be able to supply nearly infinite, clean energy.

Russia is not being left behind in this. It is reported at [3] that Russian engineers have managed to create a magnetic field which is 20 million times more powerful than that of the earths. Magnetic fields of this strength will allow them to control a thermonuclear reaction. The only thing holding them back is time: the aim is to grip previously heated plasma with this field in a few nanoseconds in order to ‘light the sun’. So far, 5 microseconds is the best achieved time.

Now this all sounds very similar to a nuclear power station but the fundamental difference between fission and fusion is the key. Fission reactions are based on splitting atoms releasing huge quantities of energy. This type of reaction is infamous for it’s involvement in the nuclear bombs dropped on Hiroshima and Nagasaki. Fusion reactions differ in that they are based on forcing the nuclei of atoms together releasing even greater amounts of energy as in the Hydrogen bomb or the sun. In the sun, the energy required to overcome the charges that repel the atoms from each other is produced by the high temperatures and the high pressures (the temperature of the sun is over 15 million degrees Celsius and the pressure is 100,000 times that on the earth’s surface.) It is not possible to create the level of pressure required but higher temperatures may be used to compensate for this ‘low’ pressure. It has been stated earlier that the reactions would be possible under temperatures of 100 million degrees. To the average man on the street it would seem that this would be difficult to attain but temperatures of around 300 million degrees have already been achieved in experimental reactors. At these temperatures, plasma is formed by the electrically charged gases. This plasma is a form of gas that has a great deal of energy looking for a way out. This has been quite a problem to solve. Even if a material was found that could contain the plasma, how would it possibly withstand such high temperatures? The answer of course came in the form of the magnetic field and it was from this idea that that the unusual shape was adopted. [4]

The devices being constructed in China and Russia are not only seen as stand-alone devices but are also expected to play a part in the International Thermonuclear Experimental Reactor (ITER). This is a project that has contributions from many different countries, including The People’s Republic of China. According to [5], it is technically ready to start construction and the first plasma operation is expected in 2016. The part of the device which is of particular interest is the superconducting magnet system. It consists of 18 Toroidal Field (TF) coils, 6 Poloidal Field (PF) coils and a Central Solenoid (CS) coil, Correction Coils. As stated at [5] superconducting saddle-shaped correction coils placed around the machine outside the TF magnets are used to accommodate field errors due to manufacturing inaccuracies or to misalignments during assembly of the magnet coils, as well as to control resistive wall mode plasma instabilities. It goes on to say that both the CS coils and the TF coils use a similar superconductor configuration. The superconductor is an Nb3Sn cable-in-conduit type. This compound is brittle and initially the wires contain separated Nb and Sn (as well as a copper matrix) which react together after a 200 hour heat treatment at 650 °C. This can only be performed after all cabling and conductor bending operations are complete, but before any temperature-sensitive coil components are added (such as the coil electrical insulation). It must also be noted that, to maintain the cryogenic temperatures needed for superconductivity, the tokamak vessel and superconducting magnets are located inside a thermally shielded cryostat.

Unlike fission which is widely regarded as being at least potentially dangerous, a fusion reaction requires leak-tight confinement, not because of the possibility of a catastrophic chain reaction but because otherwise, the plasma involved will be extinguished. As well as this advantage, there are other environmentally friendly advantages: the fuels used in these types of reactors are deuterium and tritium, both isotopes of hydrogen, and both non-radioactive. There are also no hazardous wastes produced as any reaction products are either absorbed by the surrounding lithium or are non radio-active like helium.

All in all, it would seem that we may not be at as much of a loss as we are led to believe by the sceptics. However, there may also be an interesting period of transition in which we are all asked to lay off the energy for a while. If I was a betting man though, I would put my money on the class of 2106 wondering what all the fuss was about (instead of having to worry if they’ll have enough candle-light to finish their physics assignment). It’s so simple, it’s beautiful.

REFERENCES:

[1] Angola Press (2006) China to build world’s first "artificial sun" experimental device [online], available: http://www.angolapress-angop.ao/noticia-e.asp?ID=409853 [accessed 3 May 2006]

[2] People’s Daily Online (2006) China to build world’s first "artificial sun" experimental device [online], available: http://english.people.com.cn/200601/21/eng20060121_237208.html [accessed 3 May 2006]

[3] Pravda.ru (2006) Russian engineers from the Federal nuclear centre in Saratov will attempt to light an artificial sun on the Earth.[online], available: http://english.pravda.ru/science/19/94/379/11675_technology.html [accessed 3 May 2006]

[4] People’s Democracy (2006) An Artificial Sun on Earth [online], available: http://pd.cpim.org/2003/1228/12282003_snd.htm [accessed 4 May 2006]

[5] http://www.iter.org/index.htm

1 Comments:

Anonymous Amina said...

You write very well.

7:49 p.m.  

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