An effective way to harness as much energy as possible is to install a steam turbine behind the gas turbine, in a so-called “combined cycle”. This creates a system where we capture heat energy of exhaust gases, in this case water vapour, by also placing a steam turbine in the ship’s smaller funnel. The steam turbine generates electricity that can be used in the ship for electric motors, chargers and electrical equipment. This generates more output and is more energy efficient.
Gas turbines generate hot exhaust gases that contain large amounts of energy. With a steam turbine located by the funnel, a shaft connected to a generator rotates to generate electricity. Combined cycle means that you capture much more of the energy created by the fuel used to power gas turbines and increase efficiency from 35 to about 50 per cent.
Turbines and combined cycle work in the following way:
1. Air is drawn in and compressed in a compressor.
2. The pressurized air flows into the burner where it is mixed with hydrogen gas, and ignites in the combustion chamber.
3. The expansion from the combustion drives a turbine that is connected to a shaft that drives a generator and its own compressor.
4. The hot gases can then be used by creating steam in a heat exchanger that drives a steam turbine, located by the funnel which in turn generates additional electricity.