Solid oxide fuel cells (SOFCs) have the potential to run on ammonia without the need for any pre-reforming and therefore enable effective energy conversion of ammonia to power. In this work, an ammonia based SOFC-Gas turbine (GT) system concept is proposed and assessed for the mobility sector. The model integrates a three-dimensional multiscale SOFC stack simulation based on a validated Ni-GDC/GDC/SSC button cell model with balance-of-plant component modeling. This work discusses the thermodynamics of SOFC operation and system concepts to utilize ammonia in a hybrid system for a kW-scale transportation application. System indicators and performance metrics such as efficiency, electrochemical utilization and turbine inlet temperature are evaluated and optimized. The proposed hybrid system is computationally predicted to reach efficiencies of up to 60% for pressurized operation.

SOFCs can be directly run with ammonia (NH3), which is anticipated to play a major role in future renewable energy systems due to its superior conditioning and storage characteristics. Here, we numerically investigate the performance of NH3-fueled SOFC stacks based on a high-power density ceria-based cell design by means of detailed multi-scale simulations on 1D-button cell and 3D-stack level. The model is validated based on electrochemical performance data collected on a Ni-GDC/GDC/SSC-GDC button cell at 500-650 °C. While the decomposition of NH3 at the surface of the Ni-particles is modeled by employing an elementary kinetic framework, a physically-based distributed charge-transfer model is consulted to account for the leakage current across the GDC electrolyte as a function of operation conditions. In this way, the intricate coupling between the mass, heat and charge transport phenomena, as well as the electrochemistry and thermo-catalytic chemistry can be studied on the industrially relevant scale to assist integration into a hybridized power generation system. Model predictions indicate the 120-cell stack running on NH3 to reach a very promising performance in the intermediate-temperature range.

Although solid oxide fuel cells (SOFC) offer high fuel-to-electric energy conversion efficiencies, their relatively low power-to-weight ratios make it difficult to integrate them with aircraft propulsion systems. This paper explores the feasibility of designing high throughput SOFCs for hybridization with gas turbines in aircraft powerplants. This paper explores and compares two SOFC technologies for achieving high specific power (kW/kg) with different membrane electrode assembly architectures, one with thin-film yttria-stabilized zirconia (YSZ) electrolytes and the second with high-power density gadolinia doped-ceria (GDC) electrolytes. The studies explore the operation of the respective SOFC stacks with synthetic CH4 as a carbon-neutral aviation fuel. Down-the-channel SOFC models are calibrated to experimental measurements of YSZ- and GDC-electrolyte cells at Elcogen and at the University of Maryland respectively. The model results provide a basis for determining the flow inlet conditions that enable each cell type to achieve high specific powers. The results also indicate the requirement of high airflows and upstream fuel preprocessing to sustain the high specific powers with sustainable cell operating conditions.

Air travel accounts for a significant portion of domestic and global greenhouse gas emissions. Decarbonized electric propulsion has the potential to be disruptive to replace conventional gas turbine based engines and could be an attractive solution to reduce aircraft emissions. This work aims to design a pressurized hybrid solid oxide fuel cell/gas turbine turbo generator using carbon neutral liquid fuels for narrow body commercial aircraft with high gravimetric power densities. Novel Ni/GDC based cell architectures are used to lower cell operating temperature and thereby, reduce both stack costs (e.g., interconnects and seals) and system balance-of-plant costs. There is currently limited understanding of the operating characteristics and optimum conditions for employing GDC based cells in these applications. Further, the mixed ion electronic conducting (MIEC) nature of GDC and its impact on cell voltage and electrochemical performance has yet to be quantified. This work presents a one-dimensional, down-the-channel stack model that captures physicochemical processes for an intermediate temperature Ni/GDC based fuel cell. The leakage current phenomena of MIEC anodes is captured by calculating open circuit voltage as a function of conductivity, temperature and pressure. Activation overpotentials are calculated based on published results in literature that fit exchange current densities and charge transfer coefficients based on experimental electrochemical impedance spectroscopy measurements [1,2]. Fickian diffusion for mass transport across the porous electrodes and rate mechanisms to evaluate reforming characteristics are used. The model predicts electrochemical performance for varying cell temperatures and flow rates. The distribution of overpotentials with cell temperature and current density is analyzed. Thermal management of power dense stack operating conditions is critical to understand. Thus, the stack model is also employed to within a subsystem where it is integrated with an autothermal reformer and anode gas recycle to parametrically assess operating conditions and performance, particularly towards minimizing cooling air flow requirements. Figure 1