Modelling Accelerated Ageing and Degradation of Solid Oxide Fuel Cells (MAAD-SOFC)

SOFC成功商业化的一个主要障碍是电池和电池堆组件在高工作温度下长时间暴露后的降解。寿命和可靠性是SOFC系统成功的两个最关键的问题。SOFC系统应该运行数千小时而输出功率没有显著下降。为了评估SOFC的寿命，需要进行长期测试。由于进行具有统计置信度的这种测量所需的巨大实验努力，具有改进的耐久性的电池的开发是耗时的并且因此是昂贵的。另一个挑战是分析测试电池的物理故障机制。由于在长期试验中所造成的总损害往往很低，因此很难确定主要的降解过程。在可靠性工程中，加速寿命试验（ALT）是解决这些问题的一种众所周知的方法。在ALT中，通过一个模型将从恶化试验条件下获得的寿命数据外推到正常运行条件下，该模型将数据拟合到适当的寿命分布，并使用寿命-应力关系来预测正常运行条件下的寿命。ALT的关键因素之一是降解机制不应随试验参数的恶化而改变。因此，了解SOFC在不同工况下的降解机理是非常必要的。尽管有可能，但预测这种机制非常具有挑战性。这就需要开发能够预测降解机制的适当模型。通过实验验证的模型可以作为一个有用的工具来理解SOFC的降解机制，因此将有助于设计具有所需降解速率的SOFC，以承受操作挑战。影响SOFC降解的主要因素是温度、热循环、氧化还原、负荷循环以及燃料污染物如硫和碳的中毒效应。因此，还必须研究这些因素的影响，并与ALT研究相结合。从这些实验中获得的对降解的理解和开发的模型可用于开发新材料，这些新材料可以在相同的水平下但在较低的温度下发挥作用，并且具有更好的氧化还原和毒性（硫/碳）耐受性。

A major hurdle in the successful commercialization of SOFCs is the degradation of the cell and stack components over long exposures at the high operating temperatures. Lifetime and reliability are two of the most critical issues for the success of SOFC systems. An SOFC system is supposed to run for several thousand hours without significant degradation in the output power. To assess lifetime of an SOFC, long-term tests are needed. Due to the enormous experimental efforts necessary to conduct such measurements with statistical confidence, the development of cells with improved durability is time-consuming and thus expensive. Another challenge is the analysis of the tested cells with respect to the physical failure mechanisms. As the total damage achieved during long-term tests is often low, the dominant degradation process is difficult to identify. In reliability engineering, accelerated life testing (ALT) is a well known method to address these problems. In an ALT, the life data obtained from aggravated test conditions are extrapolated to normal operating conditions by means of a model which fits the data to an appropriate life distribution and uses a life-stress relationship to project the life at normal operating conditions. One of the crucial factors in ALT is that the degradation mechanism should not change on aggravation of the test parameters. Therefore, it is imperative to understand the degradation mechanism SOFCs at the different operating conditions. Though possible, it is very challenging to predict such mechanisms. This necessitates the development of proper models which can predict the degradation mechanism. A model validated with experimental evidences can serve as a useful tool to understand the degradation mechanism of SOFCs and hence will help designing SOFCs with required degradation rate to sustain the operation challenges. The major factors which influence the degradation of SOFCs are temperature, thermal cycling, redox, load cycling and poisoning effects from fuel contaminants such as sulphur and carbon. Therefore, the effect of these factors will also have to be studied and integrated with ALT studies. The understanding gained on degradation from these experiments and the developed model can be utilized to develop new materials which can perform at the same level but at lower temperatures and also have better redox and poison (sulphur/carbon) tolerance.