Review on State of Health Definition in Relation to Proton Exchange Membrane Fuel Cells in Fuel Cell Electric Vehicles

Owing to its advantages of high energy density, quick start-up, and no emissions, the proton exchange membrane fuel cell (PEMFC) is one of the most promising power sources in transportation and has been used for automotive application for years. However, shortcomings in fuel cell key performances, such as lifetime and efficiency, characterized by state of health (SOH), restrict the large-scale commercialization for fuel cell electric vehicles (FCEV), raising demands for real-time state monitoring. Nowadays, most researchers have explored the reasons for state change from models or experiments. Nevertheless, it is in need of system-level researches on definition methods of SOH against the actual automotive application. Lacking accurate quantitative indicators, existing studies on health states are often qualitative and hence fail to consider intermediate processes. In addition, too many health indicators that describe typical physical characteristics can be used for SOH definition, which raises higher demands for the computational cost. Moreover, most researches focus on long-term degradation and overlook the importance of short-term performance changes. The research on the definition of health states aims to execute the control strategy more effectively after system monitoring, which is also influenced by key components coupled with PEMFC in powertrain system, including battery and DC/DC converter. Therefore, focusing on FCEV and based on the literature research method, latest technologies on SOH definition of PEMFCs and related estimation methods are reviewed. Based on comprehensive analyses, this paper proposes the development direction of researches on the SOH study for FCEVs, and provides helpful guidelines for the monitoring performance and optimizing control from system level for practical applications.