To make the London Underground greener and more cost effective, Transport for London (TfL) has been trialling a new system that collects and recycles waste energy from train brakes. Over the course of a week, the company says it's been able to capture electricity at a rate of 1 Megawatt hour per day -- enough to slash 5 per cent off its energy bill. The salvaged energy could also be used to run a station as large as Holborn for at least two days every week, TfL claims. The "state-of-the-art regenerative breaking system" is dependent on a new "inverter" set up at a substation near Cloudesely Road, where TfL manages the power sent to the Victoria Line. The "world-first" setup also reduces the amount of heat that's normally produced by the train's brakes. Recovering power could, therefore, keep London's Tube cooler and reduce TfL's operating costs, leading to cheaper fares. The "inverter" is now in operation full-time, but only on the Victoria line -- all the same, it's good to see TfL exploring new ways to modernise its iconic transport network.