I visited Kingston power station when I was at school. It was remarkable how so much heat could be produced by what seemed a very thin layer of coal on the moving chain grate. The coal was originally transported by barge but I think the barges had been replaced by lorries by then. It was also surprising how seldom smoke was visible. I was told that they only made smoke briefly during startup. The cooling water outlet significantly warmed up the Thames - which was very welcome when rowing nearby in the winter.
John