ST-PAUL-LEZ-DURANCE, France – Entering the construction site of the Iter facility, which will soon become the world’s largest experimental nuclear fusion project, is like entering a science fiction world.

From oversized magnets reaching more than 20m in height to massive scaffolding and huge concrete slabs, the 180ha site, approximately the size of 250 football pitches, in the south of France, is home to a dizzying array of works complex engineering.

It’s a project that promises sunshine.

Nuclear fusion has been touted as the holy grail of clean energy, producing immense amounts of energy without long-term radioactive waste, a problem associated with conventional nuclear power plants, where a uranium atom is split in two to produce electricity.

However, efforts to harness nuclear fusion energy face many technical challenges, including how the heat from the reaction can be economically harnessed so that it can be used to produce electricity.

Experts say nuclear fusion plants would take decades to become commercially viable, but various research groups, like those at Iter, continue to move forward.

By recreating the way the sun – a sphere of hot plasma – generates heat and light, nuclear fusion plants essentially replicate the same conditions that allow two forms of hydrogen to fuse.

Short for International Thermonuclear Experimental Reactor, Iter was built to test a long-held dream of determining whether nuclear fusion, a process that releases no global warming emissions as a byproduct, can be harnessed as a source of energy and eventually generate power on a commercial scale.

It is one of 130 such experimental reactors around the world – public and private – that aim to see whether recreating solar processes can propel the world toward a future weaned off fossil fuels.