Visit a Coal Power Plant: 660Mw and Beyond

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I visited a coal power plant on the weekend, and was quite impressed by the scale and enormity of the operation. 10 storey high boilers suspended from the ceiling, Turbines and generators the size of two semi trailers, etc. (I highly recommend it if you can spare the time)

Unfortunately our tour guide was a bitter, jaded security guard and was unable/unwilling to answer most of my questions.

The power plant sported pretty impressive figures for a non-supercritical coal fired plant. Each turbine consumes about 80kg/s of coal, producing 560kg/s of steam to generate 660Mw.

Given the scale and size of the installation, I'm wondering why they stop at 660Mw. Why not a gigawatt turbine? Why not two gigawatts?

I can't really think of any good logistical reason for this. Is it simply economics? Maintenance logistics? or is there some good engineering reason why powerplants aren't bigger than they are.

 

[mgb_phys]

660Mw is somethign of a standard, Drax the biggest plant in the UK has 6x660MW. I assume that it is built as a number of smaller turbines to allow it to continue operating while parts are shut down for maintainence otherwise it would be more efficent to make one large turbine.

Most reactors are also around this figure but since they generally use sea/lake water for cooling the exact steam power depends on the weather!

 

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Yeah, this particular power plant features two 660Mw turbines. It seems to be a common figure for power plants, and rather arbitrary, which is why I'm curious. I've never heard of more powerful turbines.

I assume the figure is a maximum rating given the lowest reasonable ambient/condenser temperature for that particular region or climate.