Recycled energy on Tube trains (2)

MQT on 2015-11-18
Session date: 
November 18, 2015
Question By: 
Joanne McCartney
Labour Group
Asked Of: 
The Mayor


How much does the new technology cost to implement and run? How much money will TfL save as a result of the recycled energy on each line, and in total if the technology was implemented throughout the London Underground network?


Answer for Recycled energy on Tube trains (2)

Answer for Recycled energy on Tube trains (2)

Answered By: 
The Mayor

Inverters supply power obtained through regenerative breaking, which cannot be utilised by the train fleet, back into the Tube network's other high voltage power supplies for use elsewhere on the network. Each line requires a different number of inverters as the optimum level is dependent on variable factors such as inverter location, the regenerative braking capability of the fleet, proposed train service patterns, line voltage and power system efficiency.

The cost of supply and installation of this new inverter technology, similar to that in use on the Victoria line, depends on how it is installed. As the characteristics of each substation site and line differ, so too will the cost to implement and run each inverter. For the same reason the amount of recycled energy and the resultant savings will vary from line to line.

On average, each inverter is predicted to save around £100,000 per annum. It is not possible to advise on total savings at this stage, as the application of this technology is comparatively new and requires further development. In addition, those installed underground will contribute to a reduction in tunnel temperatures.