The reason why the above is a problem for the trains is this. Suppose the full output of a small wind farm is 10 MW. Given the above distribution of wind speeds, you can have the wind power output on successive days to be something like:
ADVERTISEMENT
1,1,2,6,9,3,1,1,1,2,1,1,2,4… MW
and so-on. The average of that is 2.5 which is a fairly typical capacity factor of 25%. Now, you can imagine the train demands a constant 2.5 MW of power to run its route, so you may claim that it’s running on wind power – since that’s your average output.
But when you look at the distribution, the train is running fully on wind power on only four days of fourteen. On the other days, it’s actually getting only 52% of its power from wind.
In reality it’s worse than that, because I didn’t give it any zero days when the wind is below the cut-in speed of the turbines, because on those days the wind turbines actually draw power from the grid to keep their systems, oil pumps etc. running.
