At a research facility in the south of France, 35 countries, including the U.S., China and Russia, are working together on a project that could transform the way we think about energy.

Known as ITER – an acronym for the International Thermonuclear Experimental Reactor as well as Latin for 'the way' – the collaboration is constructing a magnetic fusion device known as a tokamak.

The ambition for the project is big. The tokamak has been designed to prove that fusion is a feasible large scale, carbon-free source of energy based on the same – and slightly mind boggling – principle which powers our Sun.

The difference between fission, which is used to produce nuclear energy today, and fusion is significant.

"Fission is taking a very large atom like uranium, you hit it and it splits it apart into two pieces," Mark Henderson, a physicist at ITER, told CNBC's Sustainable Energy. "Fusion takes… two (very) small particles, it fuses together and give(s) off energy," he added.

The potential of fusion is huge. According to the World Nuclear Association, fusion power "offers the prospect of an almost inexhaustible source of energy for future generations."

Henderson said that the Sun was around 15 million degrees Celsius, and that the aim at ITER's tokamak was to generate 150 million degrees Celsius.

"The objective there is (that) you need it to be really hot to take two charged particles and slam them together to fuse," he said. "The two charged particles are both positive. Normally they don't want to touch and you have to give them the energy so that they can actually combine and fuse together."

The ITER facility is currently under construction. European Union countries are responsible for the largest portion of costs, with the remainder shared by China, India, Japan, South Korea, the U.S. and Russia.



When it is up and running, those behind the project say that it will be the first fusion device to generate "net energy". This term, according to ITER, refers to what happens when the total energy produced during a fusion plasma pulse exceeds the amount of energy needed to power the machine's systems.

This concept of "net energy" is an exciting, tantalizing one. Is fusion, though, just a pipe dream?

"ITER is our countries coming together to answer that question once and for all: can fusion play a role in the future," William D. Magwood IV, director general of the OECD's Nuclear Energy Agency, said.

Magwood IV added that once it was operating, the tests performed at ITER would help to answer that question.