Coal is used to heat water which in turn drives a steam turbine that is used to produce power by spinning magnets past Cu coils. The faster the turbine gets turned the more electricity is produced.
When the grid hits peaks in demand the power station lifts it use of coal to increase the amount of water it heats so it can get the steam turbines moving faster. When there’s less demand for electricity they can back off the amounts of coal they add because they need less steam because they don’t have to turn the magnets as quick.
A simple way to think of it is imagine you’re driving a car up a hill. As you go up the hill you put your foot on the accelerator because the car needs more momentum to get to the top but on the downhill side you can back your foot off the accelerator because you don’t need as much power. Coal fired power stations work in a similar fashion. just like you don’t turn your car off as you go down the hill, you don’t turn off a coal station when you get a drop in electricity needs because there’s always another hill approaching.
PS Is that a simple enough explanation for you or should I try and dumb it down a bit more for you?
