Dynamic Performance Analysis of a Turbocharged PEMFC System

Abstract Proton-exchange membrane fuel cell (PEMFC) systems are one of the most promising technologies for the decarbonization of the transportation and power sectors, thanks to their high efficiency, fast dynamics, and use of hydrogen as fuel. This article investigates the dynamics of an innovative layout based on the integration of two PEMFC stacks with an electrically assisted turbocharger (TC), which is characterized by high power density and efficiencies up to almost 60%, making it very interesting for transportation applications. A detailed dynamic model of the TC-PEMFC is developed in Matlab-Simulink including all the main devices of the cathode, anode and cooling circuits. This model is used to study the dynamic performance of the system, considering the fluid-dynamic and thermal transients of its components. At first, the model is used to simulate the response of the TC-PEMFC to step changes of multiple input variables: openings of fuel valve and humidifier bypass valve, rotational speeds of TC, blower and cooling pump. These simulations highlight the strong sensitivity of the system to the fuel valve opening, making the need for a feedback controller clear. Many control logics are then implemented on the model to keep the operative parameters of the TC-PEMFC within an acceptable range. The dynamic model is used to simulate the performance of the TC-PEMFC system during different power load ramps. From the results of these simulations, it is possible to assess the effectiveness of each controller and to verify the compliance of all the system constraints. During load increases, no issues are detected. Even for the fastest considered ramp rate, equal to 100 A/s, proper operation of the system is always guaranteed, and the final power setpoint is reached in less than 5 s. On the other hand, load reductions are limited by the possibility of compressor surge. A maximum ramp rate of 35 A/s is identified in this case. To overcome this limit, a possible modification to the control logics is tested in the final part of the study.