Basic study on electric load following operation of small distributed solid oxide fuel cell system

固体氧化物燃料电池（SOFC）采用氧离子传导陶瓷材料，例如氧化钇稳定的氧化锆（YSZ）作为电解质，并且其工作温度非常高，为1200-1300 K，导致通过将其与一些合适的底循环（bottoming cycle）（例如燃气涡轮机）结合，可以实现非常高的总效率的优点，所述底循环可以利用其废气。因此，它的研究和开发一直在积极推动中大型电源。另外，由于利用燃料的水蒸气重整反应的内部发热，无需底循环，其效率可单独达到50%左右，因此也可期待作为小型分散型热电联产系统的电源。然而，SOFC在用作其电池材料的陶瓷的耐久性方面存在问题，因为其工作温度非常高，并且电池温度波动引起陶瓷的热应力。 ...更多信息 - 是的因此，其中的电池温度分布应尽可能保持恒定。然而，在小型分布式热电联产系统的情况下，通过控制电池中的平均电流密度的可变负载操作是必要的，并且该操作通常引起电池温度波动。考虑到这一事实，针对SOFC的变负载运行的建立，我们研究了平均电流密度和温度分布之间的关系，在同向和逆流型平板SOFC单电池的数值模拟。从模拟中可以清楚地看出，通过适当地调节空气利用率，温度分布的变化可以被抑制到足够低的水平，并且对于两种类型的电池都可以实现可变负载操作。为了补偿快速的负载变化和平滑的功率波动，我们建议安装一个双电层电容器之间的SOFC和负载，其效果通过数值模拟得到证实。此外，利用双电层电容器组成了实验电路，并将实验结果与仿真结果进行了比较。结果表明，虽然在瞬态响应上存在一些差异，但可以清楚地看出，实验电路几乎根据仿真工作。这表明了本研究中提出的电容控制方法的有效性。少

The solid oxide fuel cell (SOFC) adopts oxygen ion conducting ceramic materials, such as yttria-stabilized zirconia (YSZ), as the electrolyte, and its operating temperature is very high as 1200-1300 K, leading to an advantage that very high overall efficiency can be achieved by combining it with some suitable bottoming cycle, such as the gas turbine, that can utilize its exhaust gas. Its research and development, therefore, have been actively promoted for middle to large-scale electric power sources. In addition, it is now also expected as the power source for the small distributed co-generation systems, because its efficiency is expected to reach about 50% by itself without the bottoming cycle by utilizing the internal heat generation for the steam reforming reaction of the fuel. The SOFC, however, has a problem in durability of the ceramics used as its cell materials, because its operating temperature is very high and cell temperature fluctuation induces the thermal stress to the cer … More amics. The cell temperature distribution in it, therefore, should be kept as constant as possible. In the case of the small distributed co-generation systems, however, the variable load operation through the control of the average current density in the cell is necessary, and this operation usually causes the cell temperature fluctuation. Considering this fact, aiming at the establishment of the variable load operation of the SOFC, we investigate the relation between the average current density and the temperature distribution in the co-flow and counter-flow type planar SOFC single cells by numerical simulations. It is made clear from the simulations that the change of the temperature distribution can be suppressed to sufficiently low level and the variable load operation can be realized for both types of cells by properly regulating the air utilization. To compensate the very fast load change and to smoothen the power fluctuation, we propose to install an electric double layer capacitor between the SOFC and the load, and its effect is confirmed through numerical simulations. In addition, an experimental circuit using an electric double layer capacitor is composed, and the experimental results are compared with the simulation results. As a result, although there exists a little difference on the transient response, it is made clear that the experimental circuit operates almost according to the simulation. This indicates the validity of the capacitor control method proposed in this study. Less