The machine: the ST40 fusion reactor

Short of building a perpetuum mobile, the most energy-efficient process we know happens in the Sun – where two atoms of hydrogen fuse together at extremely high pressures and temperatures to form helium, and releasing energy.

For years, scientists have tried to replicate this fusion process on Earth, to create a sustainable energy solution that goes beyond fossil fuels (which contribute to climate change), traditional nuclear energy (with its radioactive waste problem) and wind and solar (which deliver power in peaks and troughs). 

In April, UK-based Tokamak Energy fired up its latest fusion reactor, the ST40. The reactor has officially achieved “first plasma,” the first step towards reaching the required temperature of 100 million degrees Celsius, at which nuclear fusion can happen. Tokamak Energy hopes to deliver fusion energy to the electricity grid by 2030. The company is using compact, spherical tokamak reactors with high-temperature superconducting magnets. Tokamak Energy was spun out of Culham Laboratory, home to the world’s most powerful tokamak, JET. It received investment from IMechE’s Stephenson Fund, which helps companies bring products to market. 

The easiest fusion reaction to replicate in the lab is between two hydrogen isotopes, deuterium, extracted from water, and tritium, produced during the fusion reaction in contact with lithium. Deuterium and tritium nuclei combine, forming a helium nucleus, a neutron and a lot of energy.