The energy needed to overcome the drag of the turbines will be more than they can produce due to efficiences being less than 100%,
eg. Engine pulling train at 100kph needs 5,000Nm
Stick a wind turbine up above a carriage which produces 50Nm and the engine would need to throttle up to 5,100Nm to overcome the extra drag. Therefore an overall loss of 50Nm. If everything were 100% efficient the engine would still nedd another 50Nm to overcome the drag of the turbine as it produced its 50Nm.
Sorry If I appeared flippant before but I see these things easily, other things I find harder.
