Modeling of cold start processes and performance optimization for proton exchange membrane fuel cell stacks

In this study, a cold start model for proton exchange membrane fuel cell (PEMFC) stacks is developed, and a novel start-up method, variable heating and load control (VHLC), is proposed and evaluated. The main idea is to only apply load to the neighboring still-active cells, and to apply external heating to certain cells inside the stack simultaneously (load is not applied to the cells fully blocked by ice, although these cells can gain heat from neighboring cells). With the VHLC method, it is found that the stack voltage first increases, then decreases due to the full blockage of ice in some of the individual cells, and finally the dead cells are heated by the other active cells and activated again one by one. Based on this method, the external heating power and the stack self-heating ability are utilized more efficiently. With proper implementation of the VHLC method, it is demonstrated that the cold stat performance can be improved significantly, which is critically important for PEMFC in automotive applications.