Race to bottle the power of the sun

Dr Bob Cyminski, Dean of applied sciences at the University of Huddersfield looks at the man’s fascination with the sun and the latest attempts to harness its awesome power

SINCE the very earliest of prehistoric times mankind has been fascinated by our sun.

Some cultures have worshipped it as a god while others have built giant observatories such as Stonehenge to track its path across the sky as the seasons change.

Over recent centuries scientists have also struggled to understand how the sun works, and how it provides the apparently limitless heat and light that is essential to sustain all life on Earth.

But it was not until 1905 that the publication of Einstein’s Theory of Relativity finally provided the key which unlocked the secrets of the sun’s source of energy.

This key is science’s most famous equation, E=mc2.

Einstein’s equation shows that mass and energy are really equivalent and that a very small mass can be converted directly into a tremendous amount of energy.

Today we exploit this principle in conventional nuclear reactors, in which the nuclei of heavy elements such as uranium are split into two or more smaller nuclei, releasing large amounts of energy in a process known as fission.

Surprisingly, the opposite also occurs. When the nuclei of two light elements collide they can fuse together to form a nucleus which is lighter than the sum of the two parts, and the missing mass is converted into energy.

This process is known as fusion. In the sun, light hydrogen nuclei fuse together to form the heavier element helium, and an enormous amount of energy is released.

For over half a century it has been science’s dream to trap and control the power of the sun here on Earth.

But how close are we to holding the sun in a bottle?

The problems seem at first to be insurmountable.

At 15 million degrees centigrade the sun is unimaginably hot. What is worse, because the extreme conditions of pressure and gravity found within the sun cannot be duplicated here on Earth, any man-made “sun” has to reach even higher temperatures — 150 million degrees centigrade!

Fortunately, at these temperatures the matter we encounter in everyday life takes on a new form. It becomes plasma, a seething gas of electrically charged particles. Because such charged particles can be confined within a magnetic field, the hydrogen plasma which is the fuel for the fusion reaction can be contained within a magnetic bottle rather than a physical bottle.

The technology for doing this was first demonstrated in Russia in the 1960s with the invention of the tokomak, a donut shaped ring of giant magnets which provide the magnetic confinement.

For almost 30 years the tokomak at the Joint European Torus (JET) project at Culham in Oxfordshire has been the world’s largest fusion experiment.

JET has been a leading centre for fusion research, holding the world record for producing 16 megawatts of fusion power for one second. However, as impressive as this might seem, it is still a long, long way from the output needed to drive a power station.

Undaunted, an international research collaboration has recently embarked upon one of the world’s greatest and most ambitious scientific challenges: the International Thermonuclear Experimental Reactor or ITER.

The collaboration has already prepared the site in the south of France where ITER will be built, and is now poised to begin construction.

Everything about the ITER fusion experiment is big. The tokomak itself will be almost 10 times larger than that at JET, weighing 23,000 tons.

It will be housed in a building almost 180 feet high. ITER is designed to operate at 150 million degrees. The plasma will be heated with intense electromagnetic radiation and by the injection of subatomic particles.

The fusion experiments are scheduled to begin in 2018, but despite the scale of the project, ITER will not be a working power station.

It will simply test whether it is indeed possible to harness the energy that is generated by the fusion process.

It may well be another half century before electricity could be generated by this virtually inexhaustible energy source.

For further information on the ITER project see www.iter.org