Efficiency Improvement of the Hydrogen Fueled Graz Cycle Using Preheating

Hydrogen is gaining significant attention as a clean energy source. However, its high cost requires the development of high efficiency power plant systems. The Graz cycle has been regarded as a promising power plant system due to its high efficiency potential and favorable technological maturity. To address this need, this study adopted preheating in the hydrogen fueled Graz cycle to improve efficiency. Two different preheating heat extraction locations were considered, and performance variations and sensitivity to key design parameters were analyzed. According to the performance analysis, efficiency increased by 0.15 %p when heat was extracted from the high pressure turbine outlet steam and by 0.33 %p when heat was extracted from the economizer outlet feedwater. According to the sensitivity analysis, efficiency increased with increasing turbine inlet temperature, whereas efficiency variation with pressure ratio was relatively small. Under all analyzed conditions, the case with heat extraction from the economizer outlet feedwater resulted in greater efficiency improvement. In addition, preheating enabled a design with a lower pressure ratio without efficiency penalties. The adoption of preheating in the hydrogen fueled Graz cycle can be an effective option to enhance efficiency.