Supercritical CO2 based waste heat recovery systems for combined cycle power plants

orc2019 Tracking Number 221

The development of sCO2 is pursued for various power applications because early and more recent studies have documented possible advantages in terms of efficiency and turbine compactness. This study on medium and large combined cycle configurations is focused on the preliminary assessment several solutions based on specific configurations of bottoming units adopting sCO2 as working fluid. The results demonstrate that the optimal bottoming unit layout is that of the so-called dual rail cycle configuration, where the pinch point problem in the low-temperature recuperator is overcome by splitting the CO2 flow leaving the compressor into two streams. For the heavy-duty gas turbine case, the dual rail power cycle allows for a net conversion efficiency similar to that of a state-of-the-art CCGT power plant with a three pressure-level and reheat steam Rankine bottoming unit. For medium power capacity gas turbines, the dual rail power cycle, instead, overperforms the conventional steam bottoming unit, which generally consists of a two-pressure level steam cycle. This result suggests that high-efficiency distributed power generation may be the target application for a first deployment of sCO2 power technology.