If coal and nuclear are out, the remaining choices are solar-wind/Simple Cycle Gas Turbine (fast response time but only 35-40% efficiency) or all CCGT (modern technology is 60+% efficiency). CCGT approach is cheaper and with the high efficiency should actually have lower CO2 emissions. Also avoids the low inertia risks now being recognized.
If coal and nuclear are out, the remaining choices are solar-wind/Simple Cycle Gas Turbine (fast response time but only 35-40% efficiency) or all CCGT (modern technology is 60+% efficiency). CCGT approach is cheaper and with the high efficiency should actually have lower CO2 emissions. Also avoids the low inertia risks now being recognized.