Performance response to operating-load fluctuations for Sub-megawatt-scale recuperated supercritical CO2 Brayton cycles: Characteristics and improvement

Abstract

The Sub-megawatt-scale supercritical CO2 Brayton cycles (SCBCs) have shown great potential in renewable energy and mobile power systems, but the response of technical performances to fluctuating operating load has not yet been completely known even for those basic cycle layouts. For this purpose, the present work investigated the performance characteristics of the global operating loads for the 0.1 and 1 MWe-scale recuperated SCBS systems. A thermodynamic model was proposed and demonstrated to be feasible to predict the cycle performance with 0.19%–9.59% relative error. Using the control-of-variables strategy, the response of cycle efficiency and net power were comprehensively examined to the 90%–110% reference load (namely ±10% fluctuations) of operating parameters, including the compressor inlet pressure, compressor inlet temperature, turbine inlet pressure, turbine inlet temperature, and mass flow rate. It was found that although the cycle performances depend upon the facility scale, the appropriate parameter matching can effectively improve the cycle efficiency and net power by 31.97% and 76.42% for the 0.1 MWe-scale cycle, and by 13.89% and 26.69% for the1 MWe-scale cycle respectively at a given the mass flow rate of CO2. The results provide a positive reference for the performance assessment and operation optimization of the small-scale recuperated SCBC systems.