High efficiency power plant with liquefied natural gas cold energy utilization

This article proposes a novel power plant comprising a closed Brayton cycle (CBC) and a Rankine cycle (RC) coupled in series with respect to the flue gases instead of a conventional combined cycle, where the cold energy of the LNG is used to cool the CBC compressor suction. The research study focuses on finding working fluids best suited to the proposed CBC–RC plant and on achieving high efficiency. The proposed working fluids that fulfil the requirements for the CBC are He, N2 and for the RC are CO2, ammonia, ethanol or water. An analysis of the power plant using different working fluids is carried out and it is ascertained that the best efficiency conditions for the CBC are achieved with He and CO2 for the RC. As a result, a thermal efficiency of 67·60%, an overall efficiency of 55·13% and a specific power of 2·465 MW/(kg s−1 LNG) is achieved.