Yes, expanding wind and solar power reduces generation costs and CO2 emissions, but it also comes with two major challenges. They are not available 24/7. And they do not provide grid stability.
When there is no wind or sun, natural gas power plants can provide dispatchable power. While demand-side management (DSM) and energy storage solutions such as batteries or pumped hydropower can also reduce residual load demands, they usually only work for a matter of hours. Gas turbines are crucial to covering residual loads for longer periods of time. And eventually gas turbines running on green hydrogen produced from surplus renewable energy will enable a closed loop for deep decarbonization of electricity production.
Traditionally, the stability and resilience of our power grids comes from conventional power plants with synchronous generators that supply indispensable grid ancillary services, like inertia, voltage control and provision of short-circuit power. In most cases, renewable energy cannot provide these services, but the rotating masses of turbine generator sets can, adding rotating inertia, stabilizing power grid voltage levels with reactive power, and strengthening the system with short-circuit power. As more large coal-fired power plants are retired, gas-fired plants will need to provide these ancillary grid services.
With an optional synchronous condenser mode, generators can remain connected to the grid year-round, even if the gas or steam turbine (in a CCPP) isn’t providing active power. A flywheel can also be added to increase inertia. The more inertia these rotating masses give to the grid, the more renewables can be connected, pushing the boundaries of renewable energy penetration.