A combined cycle power plant is more efficient than a conventional power plant because it uses a higher proportion of the energy that the fuel produces when it burns.
In a combined cycle power plant (CCPP), or combined cycle gas turbine (CCGT) plant, a gas turbine generates electricity and the waste heat is used to make steam to generate additional electricity via a steam turbine; this last step enhances the efficiency of electricity generation. Most new gas power plants in North America and Europe are of these types.
The Integrated Gasification Combined Cycle, or IGCC, is a process that turns coal into gas known as synthesis gas (syngas) before it is burnt. The impurities in the syngas, like CO2, can also be removed before it is burnt.
The syngas is often used to power a gas turbine generator for electricity whose waste heat is passed to a steam turbine system. If CO2 is removed before burning (pre-combustion) it can be stored in deep geological formations.
See future CCS options Precombustion integrated gasification combined cycle (IGCC).