It isn’t efficient. The conversion of this plant moves it from base load to “peaking” type usage since it will cost more to run.
In my mind, it is a dumb conversion. Cheaper in the long run to build a combined cycle gas turbine and only reuse the substation equipment. But with many coal being shut down in a hurry, capital investment cost may currently outweigh long term economics.
It does seem pretty stupid. You normally use energy storage when you have a huge base load of coal fired plants and insufficient intermediate generation and peakers. They are replacing coal (baseload) with combustion turbines (typically peakers, unless they are combined cycle) which by itself will greatly reduce the imbalance of the mix. I’m missing something here. It would make more sense if they were taking a huge DOE subsidy, but the excerpt suggests this is a purely commercial investment not skewed by “free” money.
What do you know? You’re not a politician.