Simulated biogas with 0.5 CO2 to CH4 ratio was used to fuel NiYSZ-based anode supported SOFC at 750oC for 22 hours. Operation on biogas was carried out after 26 hours stabilization on H2. Sn doping by infiltration technique on NiYSZ anode surface produced 4.5 times higher cell electrical performance on biogas compared to the performance of un-doped NiYSZ cell. SnNiYSZ cell showed no carbon deposited while NiYSZ cell showed 0.17mg carbon/cm2 cell. This paper presents cell electrical performance data supported by impedance spectra and mass spectra of fuel cell outlet gases. The findings in this paper may bring efforts for making biogas fuelled SOFC closer to being operable.

A new cathode ink for a solid oxide fuel cell has recently been developed (UK Patent Publication Number GB2490869). It was found to give a power density of 0.33 W/cm2 at 0.7 V at 750°C running on hydrogen. Further optimisation work has been undertaken, focusing on the dispersant: Poly(N-VinylPyrrolidone) - PVP. The effects of chain length and weight percentage of PVP have been investigated, and Poly (ethylene glycol) – PEG - was tested for comparison. PEG was found to give good performance at lower weight percentages, but had a negative impact on ink rheology at higher concentrations. Optimisation of the ink formulation increased the power at 0.7 V to 0.46 W/cm2 under identical test conditions.

The Electrochemical Society

The main problems of small scale SOFC devices are the interconnections, durability and operation on available fuels such as methane. This paper shows how anode supported micro tubular SOFCs can be interconnected more reliably then run on methane. Theory showed that by coiling a wire on the outside of the micro tube, a more reliable connection could be achieved, when compared to traditional methods of internal wiring. Experiment showed that micro tubular SOFCs can be operated for 60 hours to give a steady power output. The enhanced reliability has been tested on methane, which showed better and consistent performance by up to 9% compared to hydrogen.

Microtubular Solid Oxide Fuel Cells (µ-SOFC) are suited to a broad spectrum of applications with power demands ranging from a few watts to several hundred watts. µ-SOFC’s possess inherently favourable characteristics over alternate configurations such as high thermo-mechanical stability, high volumetric power density and rapid start-up times. Computational modelling at the design level minimises cost and maximises productivity, giving critical insight into complex SOFC phenomena and their interrelationships. To date, models have been limited by oversimplified geometries, often failing to account for oxidant supply complexities, gas distribution within pores and radiative heating effects (1-3). Here, a three-dimensional Computational Fluid Dynamics (CFD) model of electrodes, electrolyte, current collectors and furnace is considered using COMSOL Multiphysics. The distribution of temperature, current density, electrical potential, pressure and gas concentrations throughout the cell are simulated. Results show good correlation with experimental data and the model is reliable for prediction of fuel cell performance within set parameters.

The high operation temperature of solid oxide fuel cells (SOFCs) allows methane and other hydrocarbons to be directly used as fuels since they could be self-reformed inside the cells. However, carbon deposition caused by the reforming processes at the anode side usually leads to a significant reduction of triple phase boundary (TPB) and resulting a poor SOFC performance or even complete failure. According to previous research, the recycling of water vapour from the anode exhaust could possibly overcome this problem but also decrease the SOFC's efficiency. In this work, Matlab® simulink® is used to optimise the recycle rates under different conditions and for building a high performance control system that allows minimised steam addition to the methane fuel stream.

Microtubular Solid Oxide Fuel Cells (µ-SOFC) are aptly suited for powering devices with demands ranging from the order of mW to few kW. The rapid start-up time, high thermo-mechanical stability, and excellent power density by volume lend them favour over alternate configurations, particularly for portable applications (1). Interconnecting the micro-tubes, though, is a persistent issue and minimisation of conduction pathway lengths and their contribution to stack ohmic resistance is a key parameter for maximising overall performance from a tubular cell stack (2). Contacting of each electrode is most simply and typically achieved from the cell exterior at the expense of available active electrode area. Exposing the cell support, interior electrode (anode or cathode, depending on cell configuration) from the exterior can lead to fuel crossover, decreasing fuel utilisation and giving rise to accelerated degradation from local thermal ‘hot spots’ as a result of hydrogen combustion (3). In this paper a novel method of internal current collection is proposed to collect current from multiple points along the inner wall of an anode-supported tubular cell. The current collector will also act as a flow turbuliser, enhancing the flow and reducing thermal gradients within the fuel cell. Ensuring an intimate contact of the many current collection nodes to the anode and hence minimisation of contact resistance is achieved by use of brazing, depositing braze material via electroless plating. Interconnection proficiency has been studied using electrochemical performance testing, impedance spectroscopy, optical microscopy and mechanical testing.