Techno-economic analysis of supercritical carbon dioxide cycle integrated with coal-fired power plant

Supercritical carbon dioxide (sCO(2)) cycles can achieve higher efficiencies than an equivalent steam Rankine cycle at higher turbine inlet temperatures (>550 degrees C) with a compact footprint (tenfold). sCO(2) cycles are lowpressure ratio cycles (similar to 4-7), therefore recuperation is necessary, which reduces the heat-addition temperature range. Integration of sCO(2) cycles with the boiler requires careful management of low-temperature heat to achieve higher plant efficiency. This study analyses four novel sCO(2) cycle configurations which capture the low-temperature heat in an efficient way and the performance is benchmarked against the state-of-the-art steam Rankine cycle. The process parameters (13-16 variables) of all the cycle configurations are optimised using a genetic algorithm for two different turbine inlet temperatures (620 degrees C and 760 degrees C) and their techno-economic performance are compared against the advanced ultra-supercritical steam Rankine cycle. A sCO(2) power cycle can achieve a higher efficiency than a steam Rankine cycle by about 3-4% points, which is correspond to a plant level efficiency of 2-3% points, leading to cost of electricity (COE) reduction. Although the cycle efficiency has increased when increasing turbine inlet temperature from 620 inverted perpendicular C to 760 degrees C, the COE does not notably reduce owing to the increased capital cost. A detailed sensitivity study is performed for variations in compressor and turbine isentropic efficiency, pressure drop, recuperator approach temperature and capacity factor. The MonteCarlo analysis shows that the COE can be reduced up to 6-8% compared to steam Rankine cycle, however, the uncertainty of the sCO(2) cycle cost functions can diminish this to 0-3% at 95% percentile cumulative probability.

Automated summary

This study analyzed four novel sCO(2) cycle configurations to efficiently capture low-temperature heat and evaluated their performance against the steam Rankine cycle. While increasing turbine inlet temperature improved cycle efficiency, the cost increase did not significantly reduce cost of electricity (COE). Sensitivity analysis and Monte Carlo analysis indicated that COE of sCO(2) cycle could be reduced by 6-8%, but uncertainty in cost functions may limit this reduction to 0-3% at 95% percentile cumulative probability.