lets look at renewable energy then, page-38

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.