Transport for London has been trialling a new system that collects and recycles waste energy from London’s Underground train brakes.

A new “inverter” system was installed at the Cloudesley Road substation for a five-week trial. The results indicated that 1 megawatt-hour of energy can be captured per day and used to power a large station.

As well as tapping into a previously inaccessible resource and reducing its overall carbon footprint, the system would lessen the amount of heat generated by trains braking in tunnels, which in turn would reduce the energy required to operate London Underground’s cooling system.

It is estimated that the technology could save as much as £6 million ($au 13 million) a year.