Last November 2009 I was in London to receive an award "Green Apple Award for Environmental Best Practice" at the House of Commons. I was waiting at one of the tube stations to proceed towards East ham. In few minutes I was greeted by a huge air surge and it was so chill that i moved away from the platform. Then i realised that the train is entering the platform. The air in the tunnel is pushed forward by the moving train. This wind energy can be harvested in a simple way across all the tube stations. Across the entire beautiful city of London there are so many tube rail trips and hence a significant amount of energy can be harvested. In the tunnel leading in to the platform the wind energy density is  large and hence this idea can work. The main advantage is the absolute confinement of the wind within the entire stretch of the platform. that's why i said, "the wind energy density is  large".

The harnessed energy can be used to meet some of the needs in the station platforms. It is also possible to think of harvesting it all along the tunnel. I would say it is best to harness the energy just when the train is about to enter the platform from the tunnel when it pushes the whole volume of air forward.

Along similar lines, it is possible to harvest the wind energy from the trains moving into the Mass Rapid Transport System platforms in Chennai as well as in the tube rail networks in Delhi, Kolkata in India as well. 

This system can be implemented throughout the world. In fact I learned from my students this idea can be applied in Singapore, korea , Japan, United States.....

Regards, Prakash Vaithyanathan
pvaithyanathan@gmail.com

Why not give the tube sytems over to inner city freight too, and build a high level suspended monorail for passengers?

This would mean you didn't have to go underground, but could see the city as you were travelling, and take lots of lorries off the roads, with goods being delivered by tube, which could be loaded outside the city, and sent to small despatch centres based in the old tube stations.