Each power plant has a load gradient characteristic, describing to what extent it can change the output of its generators in a given timeframe. Reading the literature, I know that, for example, a gas turbine power plant has a vastly higher load gradient than a one that uses coal as its primary energy.
However, I cannot find a description which parts of the plant contribute the most to the load gradient. I can imagine that a gas-powered plant can change its output faster because there's no mill involved as in a coal power plant, but where does its gradient exactly come from?
More specifically: What constitutes the load gradient of
- a gas turbuine power plant,
- a Lignite (brown coal) power plant
- a bituminous coal power plant
- a nuclear power plant?
And why is there a difference between lignite and bituminous coal power plants?
I'd very happy to read up on the details if one could name a book. I've read several books that describe how these plants work, but fail to mention what creates or limits their load gradient.