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In this study, the implementation of a solid oxide fuel cell–gas turbine hybrid engine for primary propulsion and electric power generation in aircraft is investigated. The following three parameters, which are crucial in attaining optimal performance at any point in the flight profile, were identified: the oxygen-to-carbon ratio of the catalytic partial oxidation reformer, the fuel utilization factor of the fuel cell, and the airflow split ratio at the outlet of the high-pressure compressor. The study assesses the impact of varying these parameters within specified ranges on the performance of the hybrid system. At the design point, the system yielded a total power output of 1.96 MW, with 102.5 kW of electric power coming from the fuel cell and 7.9 kN (1.86 MW) of thrust power coming from the gas turbine. The results indicate that varying the oxygen-to-carbon ratio affected the fuel cell's fuel utilization and resulted in a slight decrease in gas turbine thrust. The fuel utilization factor primarily affected the power output of the fuel cell stack, with a minor impact on thrust. Notably, varying the airflow split ratio showed the most significant influence on the overall system performance. This analysis provides insights into the system's sensitivities and contributes to the development of more sustainable aircraft energy systems. [ABSTRACT FROM AUTHOR]

Fuel composition fluctuation could result in operation performance degradation caused by a potential failure of component or system. Therefore, this work elaborated the safe characteristic and load performance of an intermediate-temperature solid oxide fuel cell (IT-SOFC) and gas turbine (GT) hybrid system using gasified biomass gas when the composition fluctuates. The malfunction restrictions of components (such as fuel cell thermal crack, compressor surge, reformer carbon deposition) were considered in this research. Results show that the hybrid system has a high efficiency 60.78% at the design point using gasified wood chip gas, which is a useful reference for small distributed power stations. H 2 concentration variation is the most influential factor to the hybrid system output power and efficiency, followed by CH 4 , and then CO. System efficiency increases significantly with H 2 concentration increase, while decrease slightly with CO and CH 4 increase. For the system safety operation: ⅰ) when the H 2 and CH 4 fluctuates to relative proportion 90% and 97%, respectively, the reformer will suffer from the potential failure of carbon deposition; ⅱ) when H 2 increases to 116%, the TIT exceeds the upper limit 1223 K, which causes the turbine blade to burn down because of over temperature. For the effect of water variation, the system output power and efficiency will be improved with water reduction, and the efficiency can even reach up to 64.85%. However, the reformer can't work safely due to the severe shortage of water for the reforming reactions. • Study the performance of IT-SOFC/GT hybrid system using gasified biomass gas. • Research safe and load performances of hybrid system with each composition fluctuation. • Investigate safe and load performances of hybrid system with water variation. • Obtain safe operation range of hybrid system for H 2 , CH 4 , CO and H 2 O. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach to determine the safe zone for an intermediate-temperature solid oxide fuel cell and gas turbine hybrid system. The approach first ensures the compressor safety and then determines the overall system safe zone by analyzing the unsafe characteristics of main components. Safe performance of the hybrid system fueled with biomass gas at all operations is analyzed. Finally, the map of safe zone is obtained to avoid component malfunctions and system performance deterioration. Results show that the hybrid system can achieve a high efficiency 60.78%, which is an interesting reference for distributed power stations. Under all operations, two unbalanced energy zones exist, which may cause the short supply of O 2 or fuel for electrochemical reaction. The lower the rotational speed of gas turbine, the narrower the zone of carbon deposition takes place in the reformer or turbine inoperation caused by too low inlet temperature. However, the phenomenon of fuel cell thermal cracking due to over-temperature will be exacerbated. System layout also affects component safety especially for the fuel cell. In the safe zone, the system has a characteristic of high efficiency and low load with low rotational speed, vice versa. In other words, the powers and load adjustment ranges both decrease with decreasing rotational speed whereas the efficiency increases, which peaks at 63.43%. [ABSTRACT FROM AUTHOR]

In this work, detailed mathematical models of a hybrid system of an IT-SOFC (intermediate-temperature solid oxide fuel cell) and a GT (gas turbine) that is fueled by gasified biomass gas are built. Under the constraints of the working temperature of the fuel cell, mean axial temperature gradient, compressor surge, and turbine inlet temperature, the effects of operating parameters on the hybrid system are investigated mainly including RS (rotational speed), F/A (fuel/air) ratio, and S/C (steam/carbon) ratio. The electrical efficiency is 59.24% under the design condition. The power and efficiency of the system both decrease as the RS increases, with the latter decreasing from 60.95% to 49.08%. If the RS is too low, the system operation goes beyond the safety zone. In this situation, both the fuel cell and the turbine may be subjected to excess temperatures, and the compressor may easily surge. The efficiency increases from 56.5% to 61.34% with increasing F/A ratio, but an extremely high F/A ratio can cause the turbine to suffer from excess temperature. The efficiency decreases from 61.12% to 56.8% with increasing S/C ratio. The following two conclusions are drawn. First, the F/A ratio has the greatest influence on the performance of the hybrid system, i.e., its adjustment can effectively change the load in a wide range. Second, the RS and S/C ratio are suitable for load adjustment in a narrow range. [ABSTRACT FROM AUTHOR]

In order to achieve the fast load following and safe transient operation of Solid Oxide Fuel Cell-Gas Turbine hybrid system, a novel control approach by combining the multi control loops with the coordinated protection loops is proposed in this work. The coordinated protection loops can adjust the transient behavior of operation parameters on-line to avoid the undesired operation faults, such as compressor surge, reformer carbon deposition, fuel cell thermal crack and turbine blade overheat. Meanwhile, the fuzzy logic theory is introduced to self-tuning the control parameters to meet the control requirements of the nonlinear time varying system. The analysis in system transient behavior during load step changes operation indicates that the present work can realize parameters decoupling and eliminate the instability of SOFC-GT. The proposed control strategy can reduce the SOFC current overshoot by 10.8% during the load step-down operation, meanwhile, this reduces the transient maximum temperature changing rate by almost 47.7%. In addition, by changing the transient behavior of air and fuel flow, the proposed control strategy can reduce the temperature overshoot by 1.16% in load step-up operation. This leads to the transient maximum temperature gradient is decreased by 0.18K/cm. [Display omitted] • The coordinated control method combining protection loops is proposed. • Safety margins are considered in designing the control structure. • An in-depth analysis of the system transient behavior is conducted. • Fast load following and safe transient operation of SOFC-GT can be achieved. [ABSTRACT FROM AUTHOR]

This paper proposed a solid oxide fuel cell–gas turbine (SOFC-GT) hybrid system combined with anode and combustor exhaust recirculation loops. The ejector technology is introduced to perform the recirculation loops. And the hybrid system is fueled by a typical farm biogas. Furthermore, the interaction between these two recirculation is discussed. Results show that the anode recycle loop can rise the electrical efficiency of hybrid system and drop the SOFC temperature gradient. Meanwhile, the anode exhaust recirculation is beneficial to avoid the carbon deposition in reformer and prevent the fuel cell thermal crack, and the combustor exhaust recirculation can allow the system safety operated over a wider temperature range. The optimal recirculation ratio of 0.4 and 0.425 are determined in anode and combustor exhaust respectively to obtain the maximum power generation efficiency and ensure the safety operation of SOFC. The design efficiency of described system can reach to 62.21%. In addition, a parametric analysis is carried out to evaluate the coupling effect among multiple working parameters on the performance of SOFC-GT. Results indicated that the reasonable air flow rate, fuel flow rate, fuel utilization and steam to carbon ratio are the necessary prerequisite to safeguard the healthy operation of SOFC-GT. • Two recirculation loops are arranged for a biogas-fueled SOFC-GT. • The thermal management and parameters optimization of the system is investigated. • The interaction influence between two recirculation loops is conducted. • The system performance is evaluated based on the safety constraints. [ABSTRACT FROM AUTHOR]

This work focuses on investigating the adaptability of solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system for ship application under uncertain factors. The effect of rapids, wind and waves on the performance of ship SOFC-GT is analyzed. In addition, a novel control system combining fuzzy logic theory, temperature feedforward and coordination factor on-line adjustment is proposed to address the problem of load disturbances caused by uncertain factors. The results show that the proposed operation strategy can shorten the thermal response time inside fuel cell stacks by almost 49.97%, meanwhile, reducing the maximum temperature changing rate at the electrochemically active tri-layer cell composed of anode, electrolyte, and cathode (PEN structure) by around 17.86%. Moreover, the reasonable matching between air flow and fuel flow is an essential prerequisite to ensure the safe and efficient operation of ship SOFC-GT. While the SOFC-GT is working at full load, the results indicate that the fuel to air ratio cannot exceed 2.56✕10−2 g/g. Finally, an application scenario of the 5000-ton river-to-sea cargo ship sails from Nanjing Port to Yangshan Port (Eastern China) is conducted to analyze the operation characteristics of ship SOFC-GT under uncertain factors. Two set of 1000 kW SOFC-GT systems with the electrical efficiency of 64.66% is designed for the target ship, the results conclude that the operation strategy of each SOFC-GT system supports 50% load is beneficial in reducing the power tracking time and SOFC temperature overshoot. The average electrical efficiency of 61.45% and 61.04% are achieved in winter and summer typical days respectively in the whole voyage. [Display omitted] • A novel ship energy system powered by SOFC-GT is proposed. • The effect of uncertain factors on the performance of ship SOFC-GT is evaluated. • The fast and stable control approach to ship SOFC-GT is proposed. • An efficient power split approach is obtained for multi SOFC-GT systems. • Application scenario of ship sails from Nanjing Port to Yangshan Port is conducted. [ABSTRACT FROM AUTHOR]

Power-to-gas (P2G) using excess renewable sources is an effective method to reduce renewable curtailment issues in microgrid system. The produced hydrogen is versatile green fuel for different energy sectors, such as electricity, heat and mobility. In recent researches, fuel cell-based system is considered as a promising technology to consume hydrogen (H 2) generated from P2G due to high efficiency and cleanness. However, its economic and thermodynamic adaptability when coupled with intermittent renewable sources remains an open question to be addressed carefully. One of the major challenges in optimizing such system is to simultaneously capture the intraday and seasonal variation of renewable sources & load, as well as the internal thermodynamic process of critical components in appropriate modeling detail. This paper presents a multi-energy system for microgrid in which a wind-powered P2G is coupled with a detailed thermoeconomic model of solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system. A two-level multi-objective optimization of planning and operation together is proposed. For system planning, the optimal balance between the least wind curtailment rate and total life cycle cost (LCC) is determined. To facilitate the coordinate operation of system components, a power management strategy is proposed in response to fluctuations of wind power and electricity load with considerations of multiple thermodynamic safety criteria. Results show that in the selected case, the multi-energy system operates with low wind curtailment rate of 0.63% and high renewable penetration level of 90.1%. The optimized LCC of multi-energy system is £2,468,093 with wind power accounting for 68.35% of total capital investment. With the power management strategy applied, the SOFC/GT could operate under the maximum electrical efficiency of 67.1% with safety constraints satisfied, making up only half investment cost of P2G. To capture seasonal variations, both winter and summer scenarios are detailly analyzed, sensitivity analysis is also carried out to evaluate the interaction between capacities of MES components. • Designing an integrated multi-energy system of wind-powered P2G, storage and SOFC/GT. • Multi-objective optimization method coordinately integrating both design and operation levels by genetic algorithm. • Proposing a novel power management strategy to avoid subsystem unbalance problem. • Wind energy penetration of 90.1% is achieved with low curtailment rate of 0.63%. [ABSTRACT FROM AUTHOR]