Is it possible to generate electricity using a wind turbine mounted on a moving train?
Theoretically yes, it is possible to generate electricity by taking advantage of the speed of a moving train against still air of the atmosphere. What is required is a wind turbine of suitable design fixed on the roof of the engine or a coach.
When the train is moving at some speed, the blades of the wind turbine will tend to rotate due to air hitting the blades at the speed of the train. This will produce electricity just similar to the electric power produced in a wind turbine. May be this energy can be used in lights and fans of the coaches.
But the arrangement will be very cumbersome as compared to the one which is used to produce electric power in the coaches through a dynamo/generator mounted on the under-frame of the coaches and its rotor taking motion from the axles.
In any case, the power generated will be less than the extra energy required to move the train against the drag of the air due to mechanical disadvantage and other friction as a greater part of the energy is lost in heat due to friction and drag.
Another serious disadvantage of this arrangement shall be the increase in the moving dimensions of the train fitted with wind turbine on the roof of the engine/ coaches which shall in turn increase the vertical clearances required under bridges and in the tunnels. Thus on practical considerations, the requirement of electric power is never met from wind.
In case of fully air-conditioned trains, like Rajdhani Express, the electric energy needed for aircondioning and lights is met from a separate generator car using diesel power. In case of other trains, the energy requirement is met from under carriage generators which are run from power taken from the moving axles. (Courtesy: S.P.S. JAIN, Former Member Engineering, Railway Board, Indian Railways, Greater Noida, Uttar Pradesh)