Warm standby would involve burning coal...
The newest coal plant in the UK is not exactly modern. Drax phase 2 was opened in 1986, so is 27 years old.
Coal generates a third of the electricity (or did when I was there), probably nearer 25% now. Nuclear 19% - probably 15% now, and the majority of the rest is gas.
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Interesting, I was under the impression it was a fairly common affair sending power to Europe and back.
I'd always assumed powerstations just remain on unless they are shut down for maintainence. Are turbines regularly shut down and spun up? Is every powerstation expected to have a fixed output all the time (eg Drax is expected to output x number of kV and Sizewell y number?
Keeping the supply right is a balancing act based upon the frequency of the power (all power is AC 50 Hz).
Too much power supplied into the grid causes the frequency to exceed 50 Hz, so you need to reduce supply.
Too much demand means the frequency falls, so you either need to increase supply or in extreme cases reduce demand. The system can actually disconnect parts of the grid automatically to protect the rest of the system.
Most demand is forecast using weather forecasts, and by looking at previous real figures. As you would expect, demand is low until about 6am and gradually rises until about 9am where it spikes up. It's sustained until about 5pm where it starts to fall off, then gradually falls off until at about 11:30pm the demand is fairly low again.
Most power stations will know what is expected of them, and some are deliberately not run at full capacity so they have a spinning reserve available. They feed just enough steam to the turbines to regulate the frequency.
The idea of this is that if another station trips, then this can quickly be taken up with the stations that are designated as spinning reserves.
They aren't generally used for TV Pick ups because it's a very short term (about 10 minute) interval. Hydro provides that instant fix.
There are also some warming stations. effectively stations that can be ready to roll in 45 minutes. Useful when a station trips for a major fault, as it allows the spinning reserve stations to come down from full output.
There are various other factors including industrial customers who can disconnect some supplies at very short notice until the capacity is brought back up to strength.
Just as a point of correction, power generated is measured in watts. The scales generally in use for a power station are megawatts MW, and in the grid are gigawatts GW.
