We mostly already have the combined-cycle gas turbines, and are burning NG on them, so their capital cost is already sunk.
Until enough renewable generation is built out, it will be silly to build storage, so the turbines will continue burning NG, just increasingly mainly at night and on dark, calm winter days. As their duty cycle declines, their total annual operating cost falls in proportion. As chemical synthesis and compressed or liquified air storage gets built out, later, the fraction of their (reduced) operating time they spend driven by those instead of NG increases. As non-synfuel storage capacity (battery, pumped hydro, mineshaft gravitic, buoyancy) increases, running time and maintenance load declines further, as those pick up more load. Synfuel and compressed air will be mixed into NG in proportion increasing with stock on hand, rather than running on one fuel for a while and then another. Eventually NG falls out of the mix.
Operating the turbines only when the renewables and non-fuel storage are not supplying enough power cuts the maintenance load, therefore operating cost per unit calendar time. Not running does not mean you are not getting revenue: revenue comes in for the renewable-generated power, produced at near-zero marginal cost.
Running a turbine only sometimes extends its total life, so its capital cost is amortized over just as many kWh produced, either way, just longer in, again, calendar time.
Until enough renewable generation is built out, it will be silly to build storage, so the turbines will continue burning NG, just increasingly mainly at night and on dark, calm winter days. As their duty cycle declines, their total annual operating cost falls in proportion. As chemical synthesis and compressed or liquified air storage gets built out, later, the fraction of their (reduced) operating time they spend driven by those instead of NG increases. As non-synfuel storage capacity (battery, pumped hydro, mineshaft gravitic, buoyancy) increases, running time and maintenance load declines further, as those pick up more load. Synfuel and compressed air will be mixed into NG in proportion increasing with stock on hand, rather than running on one fuel for a while and then another. Eventually NG falls out of the mix.
Operating the turbines only when the renewables and non-fuel storage are not supplying enough power cuts the maintenance load, therefore operating cost per unit calendar time. Not running does not mean you are not getting revenue: revenue comes in for the renewable-generated power, produced at near-zero marginal cost.
Running a turbine only sometimes extends its total life, so its capital cost is amortized over just as many kWh produced, either way, just longer in, again, calendar time.