Wind turbines could extract energy from braking underground trains

Mark Kilby from Bournemouth University has come up with the idea of using a ring of wind turbines round the inside of the tunnel approach to a London Underground station to extract and harness some of the energy from slowing trains.

He calculates that if each turbine was 250mm in diameter and had five blades, the 16m/s speed of the air being dragged along by the train would spin the turbine at 2,444 rpm. This would produce 150V at 15A or 2250W of power for the 20s that it would take each train to go past. Just four turbines would then produce 43.3 MJ per day. He has designed suitable turbines using software available online at Club Cycom and then performed finite element analysis on the blades using the FEA facility within SolidWorks. He says he would envisage making the turbines out of aluminium alloys rather than steel in order to avoid build up of magnetised brake dust. At present, slowing London Underground trains dissipate all their kinetic energy by applying their brakes. There is no attempt to recover energy by regenerative braking. The heat energy released by the braking trains has to be removed by ventilation systems. This is just one of a series of student inventions that is to form part of a longer article in the September edition of Eureka