Steam-Injected Gas Turbines

Among cogeneration and central station power generating technologies, gas turbine systems are attractive largely because of their low capital cost and simplicity. However, poor part-load efficiencies have restricted simple-cycle gas turbines largely to base-load cogeneration applications, while relatively low efficiencies for the production of power only have restricted gas turbines largely to peaking central station applications. Steam-injected gas turbines overcome cogeneration part-load problems by providing for steam in excess of process requirements to be injected into the combustor to raise electrical output and generating efficiency. For central station applications, proposed steam-injected gas turbines would achieve higher efficiencies at smaller capacities than any existing commercial technology, including combined cycles. Their high efficiency and expected low capital cost would make them highly competitive for baseload power generation. This paper provides an overview of steam-injection technology, including performance calculations and an assessment of the economic significance of the technology for cogeneration and central station applications.