Gas Turbine Power Plants - Single Cycle and Combined Cycle
Design efficiencies of around 60% can be achieved with modern combined cycle gas turbine power plants. Our team is usually concerned with unit sizes starting from approximately 5 MW for single cycle gas turbine units up to combined cycle power plants with multiple units yielding an electricity output of some thousands MW. Those large scale power plants are often combined with desalination plants.
Although their name implies differently, gas turbine power plants can be powered by different kinds of gases: light and heavy fuel oils and - if particular gasification processes (e.g. IGCC) or pre-treatment are applied - also with coal, heavy oils, refinery residues or solid waste.
Single Cycle Power Plants (SCPP)
Gas turbine power plants designed as single cycle power plants are often built to cover peak electricity demands due to their short start-up time and in case no cooling water is available at the plant site. They may moreover suit particular industrial processes which require electricity and heat in form of hot flue gas. In a single cycle arrangement the gas turbine directly drives the electrical generator.
Combined Cycle Power Plants
In combined cycle power plants the thermal energy of the hot gas turbine exhaust gases is further utilized to generate steam in a heat recovery steam generator (HRSG).
So called 1+1 units comprise one gas turbine, one HRSG and one steam turbine. Those units can be designed as single shaft arrangement where the gas turbine and the steam turbine are combined on one shaft to drive the generator or as multi-shaft arrangements where the gas turbine and the steam turbine each drive an individual generator. Combined Cycle Power Plants comprising two or three gas turbines and HRSGs with one steam turbine, so called 2+1 respectively 3+1 units, are inherently multi-shaft arrangements.