In this study, a novel current collecting method was designed and demonstrated by inserting a metal wire brush into the anode supported micro-tubular SOFC. The new design enables a tight and stable contact between the wire and the inner wall of the anode which leads to a fine performance of the SOFC. Different kinds of metal wires were applied, where the copper wire brush (CZWB) shows a better performance than the stainless steel wire brush (SSWB). At a temperature of 700℃ and a fuel feed of hydrogen, the SOFC using CZWB can achieve a maximum power density of 290 mW/cm2 and an ohmic resistance of 0.66 Ω∙cm2. And the brush size has been approved to have little effect on the ohmic resistance. A 108 h long-time discharge test was carried on, resulting with a degradation rate of 1.728‰/h and indicating a relative stability.

In this study, a power generation module was demonstrated, i.e. micro-tubular solid oxide fuel cell (SOFC) integrated with a catalytic partial oxidation (CPO) reactor of n-butane, which has great potential in compact portable applications. The characteristics of CPO reforming were evaluated on Rh/Al2O3 catalyst under various operating conditions. When the temperature was 800℃ and C/O ratio was 0.9, a maximum n-butane reforming efficiency of 85.86% and a selectivity of H2 or CO over 92% were obtained respectively. The electrochemical characteristics of the function module were performed also on n-butane. The peak power density of the function module was 274mW/cm2 at 690℃ and a flow rate of 150ml/min. Besides, the module could endure harsh temperature change rate well above 400℃/min in thermal cycling, indicating its potential for fast start-up. Further, high temperature heat-pipes could be easily introduced to this module for quickly removing local excess heat and realizing extremely fast start-up.

A multi-physical field coupled three dimensional model of large-scale micro-tubular solid oxide fuel cell (MTSOFC) stacks was established in this study. The effects of structural parameters and operating conditions, namely configuration of the tube array, diameter, length, distance between tubes, the flow rate and flow path of air, on the stack performance were studied. The triangular array is more compact in space and can achieve higher volume specific power than the square array. However, the more concentrated arrangement also results in a higher local temperature and temperature difference, which is challenging for long-term stability. According to the simulation results, smaller tube diameter and distance between tubes lead to higher volume specific power, with the former having a marginal effect. A longer tube can reduce the axial temperature gradient, which is conducive to long-term operation stability. Increasing the air flow rate of the cathode is the most effective method to reduce the highest temperature. Furthermore, the co-flow arrangement is found to be more helpful to take away the heat generated by the stack than the counter-flow arrangement. Based on the simulation results, the structural parameters and operation conditions suitable for a large-scale micro-tubular SOFC stack are decided, considering the output power, long-term stability, and mechanical strength. The model is demonstrated as a powerful tool for the design and optimization of MTSOFC stacks. Key words: Micro-tubular SOFC Stack; Array Configuration; Structure Parameter; Operation Condition; Volume Specific Power

Blending hydrogen into natural gas grid can effectively reduce carbon emissions and promote the development of the hydrogen economy. Utilizing hydrogen-natural gas mixtures through internal reforming solid oxide fuel cells (SOFCs) can convert the chemical energy of the fuels direct into electricity, which is a promising technology for combined heat and power systems. In this study, a three-dimensional model for an internal reforming solid oxide fuel cell unit is developed coupling chemical and electrochemical reactions, mass, momentum, and heat transfer processes. The influences of the hydrogen addition on the distributions of temperature, gas compositions, and current density are studied by changing the hydrogen blending ratios in inlet gas mixtures. The simulation results show that the addition of hydrogen affects the coupling of the endothermic reforming reactions and exothermic electrochemical reactions, which leads to improved temperature uniformity and higher current density of the SOFC unit compared with pure methane feeding.

In the Acknowledgement, the following sentence "The authors acknowledge the Project (218YFB1502201) supported by National Key R&D Program of China" should be changed to "The authors acknowledge the Project (2018YFB1502201) supported by National Key R&D Program of China".