Thermal regenerative design of a fuel cell cogeneration system

• Published in: Journal of power sources 2012-12, Vol.219, p.317-324
• Main Author: Hwang, Jenn-Jiang
• Format: Article
• Language: English
• Subjects: Applied sciences; Cogeneration system; Devices using thermal energy; Direct energy conversion and energy accumulation; Efficiency; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Heat exchangers (included heat transformers, condensers, cooling towers); Proton exchange membrane fuel cell; Thermostat
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2012.07.069

The objective of the present work is to design and fabricate a thermal management system (TMS) that commands a proton exchange membrane fuel cell (PEMFC) based cogeneration system to generate the electricity and hot water efficiently. Parametric studies include the external load (PL) and the regenerative temperature (TR). A thermostat valve is employed to optimize the stack operation temperature, while a thermal regenerative unit (TRU) containing a planar heat exchanger is used to recover the heat dissipated by the stack. First, the dynamics of thermal and electrical characteristics such as voltage, current, power, coolant temperature, coolant flow rate, and hydrogen flow rate are measured to check the reliability of the TMS. Then, the effectiveness of the planar heat exchanger is determined to verify the cooling ability of the TRU. Moreover, the transient system efficiencies, including electrical efficiency, thermal efficiency, and overall efficiency are determined. Furthermore, the effect of the regenerative temperature on the time-averaged system efficiencies is examined under different external loads. Finally, an empirical correlation for time-averaged overall efficiency is proposed for helping in design of the PEMFC cogeneration system. ► The thermal regenerative unit recovers the heat dissipated by the stack. ► A thermostat valve has optimized the stack operation temperature. ► The effectiveness of the planar heat exchanger rounds 100% in the steady state. ► The thermal efficiency of the fuel cell cogeneration system is about 20 ± 8%. ► The overall efficiency of the cogeneration system is as high as 75% at PL = 2.5 kW and TR = 54 °C.