Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Thermodynamic modeling and analysis of a novel PEMFC-ORC combined power system Guokun Liu a , Yanzhou Qin a, ⁎ , Jianchao Wang b , Can Liu a,c , Yifan Yin a,c , Jian Zhao d , Yan Yin a , Junfeng Zhang a , Obed Nenyi Otoo a a State Key Laboratory of Engines, Tianjin University, Tianjin, China b Tianjin Internal Combustion Engine Research Institute, Tianjin, China c School of Automotive Studies, Tongji University, Shanghai, China d Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada ARTICLE INFO Keywords: PEMFC ORC Cooling system Waster heat recovery Thermodynamic modeling Exergy analysis ABSTRACT In this study, a novel proton exchange membrane fuel cell (PEMFC) system is proposed, which uses organic working fluid to cool the fuel cell stack directly and recovers the waste heat by combining with an Organic Rankine Cycle (ORC) system. A thermodynamic model of each component and subsystem is established for the combined PEMFC-ORC system. The influence of the PEMFC stack inlet temperature and current density, the ORC working fluid, superheat temperature and saturation pressure on the system performance is studied. The flow and distribution of energy and exergy in the whole PEMFC-ORC system are analyzed comprehensively. It is found that the system performance indicators reach the optimum when the stack inlet temperature is about 343.15 K. Lower current density improves the system efficiency, but reduces the system power density. R245fa shows the best performance among the five organic working fluids investigated for the designed ORC system. Higher superheat temperature and saturation pressure of the organic working fluid in the cycle improves the ORC efficiency. The PEMFC stack has the largest exergy loss in the system, and the cathode side heater and air compressor also contribute much to the large power and exergy loss. The optimization of these components should be the focus of system performance improvement. 1. Introduction Fuel cell is recognized as a promising technology in the context of decreasing oil resource consumption and greenhouse gas emissions. As the most popular type of fuel cell, proton exchange membrane fuel cell (PEMFC) has some key advantages such as low operating temperature, high power density and long operating life [1]. There have been a lot of researches on PEMFC in recent years, and most of them are focused on the key components of the PEMFC stack, such as the cooling plate [2], gas flow channel [3,4], microporous layers [5,6] and bipolar plates [7]. As many fundamental technical obstacles overcoming, the PEMFC be- comes viable for many applications and is being commercialized [8,9]. The PEMFC stack needs equipping with a series of auxiliary equipment during the operation, such as air compressor, humidifier, heat exchanger, hydrogen recirculating device, to form a complete power system. All these auxiliary equipment in the system consume a considerable amount of power and reduce the overall system efficiency [10]. Besides, the waste heat generated by the PEMFC stack is nearly equal to its power output under normal operating operations, so the electric efficiency of vehicular PEMFC stack is usually limited to 50%. Therefore, the recovery and utilization of the PEMFC stack’s waste heat has great potential to improve the efficiency of the PEMFC system [11]. There are some researches on waste heat recovery of fuel cells and the most common method is through combined heat and power (CHP) systems. Kwan et al. [12] applied a thermoelectric generator (TEG) to the PEMFC system and made an optimization investigation based on the genetic algorithm. Hwang et al. [13,14] integrated a novel heat re- covery unit into a PEMFC cogeneration system, and the maximum ef- ficiency of the proposed CHP system is near 81% according to their results. Shabani et al. [15] experimentally studied the potential of ex- tracting thermal energy and electric energy from PEMFC, and improved the economy of providing energy for remote homes by using computer simulation. Chen et al. [16] proposed a combined cooling, heating and power system (CCHP) of PEMFC, which can provide electric power, space heating/cooling and hot water for apartment simultaneously, and carried out a multi-criteria assessment study on it. Guo et al. [17] https://doi.org/10.1016/j.enconman.2020.112998 Received 5 February 2020; Received in revised form 3 May 2020; Accepted 17 May 2020 ⁎ Corresponding author. E-mail address: qinyanzhou@tju.edu.cn (Y. Qin). Energy Conversion and Management 217 (2020) 112998 0196-8904/ © 2020 Elsevier Ltd. All rights reserved. T