The first process includes a combustion turbine that operates like a jet engine, drawing in and compressing outside air to a high pressure. The pressurized air mixes with natural gas and then burns, creating hot exhaust gases. These gases power a combustion turbine, spin a generator and ultimately make energy.
The second process sends the hot exhaust gases from the combustion turbine generator to a heat recovery system. This system captures heat from the hot exhaust gases to produce steam to rotate a steam turbine generator and make more energy.
Combined-cycle technology is highly efficient because of this heat recovery system. Without this system, all of the heat from the hot exhaust gases would be wasted and released to the atmosphere instead of captured and reused to make more energy.