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Compressed air energy storage systems offer an effective solution to the intermittency and fluctuation challenges associated with renewable energy grid integration. A significant challenge in current compressed air energy storage systems is the substantial energy loss incurred during the discharge due to throttling processes, which is crucial for improving round-trip efficiency. Therefore, an ejector-enhanced compressed air energy storage system (EA-CAES system) is proposed in this study, characterized by the employment of ejector to reduce the pressure loss caused by the throttling process. The performance of the system is analyzed from both sensitivity analysis and multi-objective optimization. Conventional exergy analysis is used to estimate the locations and magnitudes of exergy destruction within the system, and advanced exergy analysis is applied to determine the interactions among components and to identify the potential for system performance improvement. The results showed that, compared to the advanced adiabatic compressed air energy storage system, the round-trip efficiency of the proposed system increased by 3.07%, and the total exergy destruction during the pressure reduction process was reduced by 401.9 kW. As for the sensitivity for components in the EA-CAES system, the avoidable exergy destruction of the ejector is the most sensitive to changes in all parameters, followed by the unavoidable exergy destruction of the heat exchangers in the charging and discharging processes influenced by the air storage pressure and throttling pressure, respectively. Finally, based on the best trade-off solution among multi-objective optimization, the ejector, turbine, and compressor should be paid special attention to the system improvement according to the advanced exergy analysis. [ABSTRACT FROM AUTHOR]

Summary: The paper proposes a novel combined heating and power (CHP) system integrated with solid oxide fuel cell (SOFC) and supercritical CO2 (SCO2) partial preheating cycle to improve the energy utilization rate by employing the SCO2 cycle to recover the waste heat from the SOFC. The SCO2 partial preheating cycle can not only improve the net output power but also preheat the air supplied to the SOFC for enhancing the system efficiency. Sensitivity analysis is implemented to study the influences of six key parameters (ie, fuel flow rate, excess air ratio, fuel utilization factor, CO2 turbine inlet temperature, CO2 compressor pressure ratio, and CO2 split ratio) on the proposed system in terms of thermodynamic behaviors. And then the optimal operating conditions for the different objectives are determined by parametric optimization. The results indicate that the optimal overall electrical efficiency and CHP efficiency of the proposed system are 72.84% and 83.83% respectively, while the exergy efficiency can achieve 70.84%. Furthermore, the best trade‐off result is obtained with the energy output of 434.71 kW and the exergy efficiency of 64.28%. Finally, the investigation demonstrates the fuel flow rate is the most sensitive parameter which should be determined with the comprehensive consideration of the efficiency and energy output, and the lower excess air ratio and higher CO2 turbine inlet temperature are preferred for power generation. [ABSTRACT FROM AUTHOR]

In order to study the influence of graphene filling on thermal conductivity and thermal stability of different polymers under the same preparation method, three kinds of polymer composites of GE/PA6. GE/PP and GE/HDPE were prepared by melt blending. The results show that, it was effective for graphene to enhance the thermal conductivity of three kinds of polymers. When the mass fraction of filled graphene reached 10% the thermal conductivity of GE/PA6 increased from 0.32 to 1.3 W/(m ⋅ K), that of GE/PP increased from 0.37 to 1.15 W/(m ⋅ K). and that of GE/HDPE increased from 0.62 to 1.13 W/(m ⋅ K). The prepared graphene polymer composites were studied by thermogravimetric analysis. By comparing pure polymer and graphene polymer composites with graphene mass fraction of 1%, 5% and 10%, the thermal stability of PA6 was gradually improved, and the thermal stability of PP and HDPE first decreased and then increased. [ABSTRACT FROM AUTHOR]