An evaluation of advanced combined cycles

The main objective of this investigation is to identify and assess advanced improvements to the combined cycle such as gas turbine firing temperature, pressure ratio, combustion techniques, intercooling, enhanced blade cooling schemes and supercritical steam cycles that will lead to significant performance improvements in coal based power systems. This assessment is conducted in the context of conceptual designs that advance state-of-art combined cycles and result in an 8% reduction in heat rate over a coal based Integrated Gasification Combined Cycle (IGCC) plant utilizing an H class gas turbine technology with steam cooling. This efficiency goal for the study was set by the United States Department of Energy. H class gas turbines are commercially offered by General Electric (GE), Mitsubishi and Siemens for natural gas based combined cycle applications with 60% efficiency (LHV) and it is expected that such machines will be offered for syngas applications within the next 5–10 years, while our investigation looks further beyond that time frame. The levelized cost of electricity for an IGCC utilizing the H class gas turbine is $86/MW h while that for the advanced IGCC identified in this investigation consisting of an intercooled gas turbine with a firing temperature that is 340 °C higher is $79/MW h which is a significant 8% reduction.