β Scribed by M. Sundaresan; R. M. Moore
No coin nor oath required. For personal study only.
For passenger fuel cell vehicles (FCVs), customers will expect to start the vehicle and drive almost immediately, implying a very short system warmup to full power. While hybridization strategies may fulfill this expectation, the extent of hybridization will be dictated by the time required for the fuel cell system to reach normal operating temperatures. Quickβstarting fuel cell systems are impeded by two problems: (i)βthe freezing of residual water or water generated by starting the stack at below freezing temperatures and (ii)βtemperatureβdependent fuel cell performance, improving as the temperature reaches the normal range. Cold start models exist in the literature; however, there does not appear to be a model that fully captures the thermal characteristics of the stack during subβfreezing startup conditions. Existing models lack the following features: (i)βmodeling of stack internal heating methods (other than stack reactions) and their impact on the stack temperature distribution and (ii)βmodeling of endplate thermal mass effect on end cells and its impact on the stack temperature distribution. Unlike a lumped model, which may use a single temperature as an indicator of the stack's thermal condition, a model considering individual cell layers can reveal the effect of the endplate thermal mass on the end cells, and accommodate the evaluation of internal heating methods that may mitigate this effect. This paper presents and discusses results from simulations performed with a new, layered model.
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The voltage dynamic properties of PEM fuel cell stack have been analyzed through experimental investigation. Different behaviours between voltage overshoot and undershoot are found under load commutations. A semi-empirical dynamic model for stack voltage is introduced on the basis of experimental in