3 ms·

Nope. Adding power to the grid is +X MW. Removing power to the grid is -X MW. Not producing any power is 0 MW.

• vidarh 9y ago
  That's true when looking at an individual plant, but is not directly relevant when you're looking at the grid as a whole (though it may be an issue when you have transmission limitations), where the problem is that at some point you have a supply of +2X MW, and demand is only X MW, and you need to deal with the X MW of oversupply. If one of the suppliers can then turn off X MW of supply rapidly, that has the same effect as if you add X MW of demand. At a hydro plant you have multiple options: You can bypass the turbines; you can close the dam, as long as it's not near capacity; if you have a lower reservoir you can close the dam and pump water up to the upper reservoir. All of these help reduce the excess supply, but pumping up does so by increasing demand and reducing supply, and the other two options reduce supply. You can of course do pumped storage without normally producing electricity too - in places where the only convenient location for a reservoir is not "in line" with a water source with sufficient fall height, you can still pump up to a convenient location, in which case the plant is basically "only" storage.