This paper presents thermodynamic analysis and exergy analysis in oxy-hydrogen cycle compared to gas turbine combined cycle (GTCC) with H2/Air combustion and GTCC with LNG/Air combustion, using thermal efficiency analysis software (EnergyWin®). First, the thermal efficiency for oxy-hydrogen cycle was clarified as functions of gas turbine inlet temperature and pressure. The overall thermal efficiency (LHV basis) of oxy-hydrogen cycle resulted in 2-11% points higher than that of GTCC with H2 or

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... G. Exergy loss for combustor, which decreases by 2-4% points, is the most improved. One of the reasons is that setting up higher pressure ratio of compressor for oxy-hydrogen cycle enables to adapt to higher combustor inlet temperature. It indicates oxy-hydrogen cycle can achieve high thermal efficiency. On the other hand, the application limit of state quantity such as compressor outlet temperature for oxy-hydrogen cycle, because of the strict condition with current thermal power plant technology, was also clarified. The effect of high pressure turbine (called steam turbine 1 in this paper) inlet pressure is analyzed for oxy-hydrogen cycle. Furthermore, net thermal efficiency of oxy-hydrogen cycle considering oxygen production is also estimated to clarify its performance.