The energy efficiency of an extended range unit involving a polymer exchange membrane fuel cell stack

¹ AGH University of Krakow, Faculty of Energy and Fuels, 30-059 Krakow, Poland
² Poznan University of Technology, Faculty of Mechanical Engineering, 60-965 Poznan, Poland
³ Lviv Polytechnic National University, Department of Business Economics and Investment, Lviv 79059, Ukraine
⁴ AGH University of Krakow, Faculty of Mechanical Engineering and Robotics, 30-059 Krakow, Poland

^* Corresponding author: potoczek@agh.edu.pl

Abstract

This article presents the results of experimental investigations on an advanced model of a polymer exchange membrane fuel cell (PEMFC) stack designed to serve as a charging unit for electric vehicle batteries or off-grid distributed power sources. The assembled 720 W PEMFC stack comprises two 360 W modules that can be electrically connected in series or parallel. A liquid cooling system for the PEMFC stack has also been constructed. The dependencies – voltage (U) versus current (I) and current (I) versus electrical power (P) – for single modules, as well as for the electrically connected two-module PEMFC stack, are determined. Additionally, the hydrogen utilization versus the electrical power (P) of the PEMFC stack is examined. The electrical efficiency of the PEMFC stack varies between 42% and 50%, depending on the electrical power. An adjustable DC/DC converter, operating in two modes (step-down or stepup), is proposed as a device to integrate a lithium-ion (Li-ion) battery pack with approximately 720 W PEMFC stack. The electrical architecture of the integrated system, comprising the PEMFC stack, DC/DC converter, and Li-ion battery pack, is investigated and discussed in this paper. It was found that the electrical efficiency of the proposed DC/DC converter varies depending on the electrical power, reaching a peak efficiency of 95%– 98%. The environmental benefit, in terms of reducing CO₂ emissions when charging the battery, was also identified.