You can designate a place where coal is unloaded.
You can designate a track or two to hold loads waiting to be dumped and empties waiting to be picked up.
Powerplants GENERALLY had some kind of substation (Poor choice of word term but bear with me) to allow transmission of power somewhere.
There is another thread on these forums that shows a power plant with some good ideas and pictures.
http://www.trains.com/trccs/forums/1086904/ShowPost.aspx