Thermoeconomic analysis of a novel zero-CO2-emission high-efficiency power cycle using LNG coldness

This paper presents a thermoeconomic analysis aimed at the optimization of a novel zero-CO2 and other emissions and high-efficiency power and refrigeration cogeneration system, COOLCEP-S (Patent pending), which uses the liquefied natural gas (LNG) coldness during its revaporization. It was predicted that at the turbine inlet temperature (TIT) of 900 °C, the energy efficiency of the COOLCEP-S system reaches 59%. The thermoeconomic analysis determines the specific cost, the cost of electricity, the system payback period and the total net revenue. The optimization started by performing a thermodynamic sensitivity analysis, which has shown that for a fixed TIT and pressure ratio, the pinch point temperature difference in the recuperator, ΔTp1, and that in the condenser, ΔTp2 are the most significant unconstrained variables to have a significant effect on the thermal performance of novel cycle. The payback period of this novel cycle (with fixed net power output of 20 MW and plant life of 40 years) was ∼5.9 years at most, and would be reduced to ∼3.1 years at most when there is a market for the refrigeration byproduct. The capital investment cost of the economically optimized plant is estimated to be about 1000 $/kWe, and the cost of electricity is estimated to be 0.34–0.37 CNY/kWh (∼0.04 $/kWh). These values are much lower than those of conventional coal power plants being installed at this time in China, which, in contrast to COOLCEP-S, do produce CO2 emissions at that.