Experimental Investigation On Power Efficiency Of PEMFC Stack And On Combined Power And Heat Supply Of PEMFC-Thermal Engine

Proton exchange membrane fuel cells (PEMFC) is considered as a preferred clean, high efficient power generation technology in the 21st century for its numerous superior features such as high energy conversion efficiency, low pollution to environment, quiet, fast start-up and working at near room temperature etc. In practical application, however, the overall efficiency of PEMFC can't be optimistic, for the electric efficiency of PEMFC is affected by many operational parameters, which result in lower electric efficiency, and besides, waste heat produced in PEMFC accounts for 40%~60% of the whole energy, but the heat is in low grade, so it is difficult to be used. For these reasons, the experimental research on PEMFC stack and PEMFC-thermal engine combined power and heat supply (CPHS) is carried out in the thesis, the main content and results are as follows.The influencing mechanism of temperature, pressure and humidity on electric efficiency in different loads is investigated, based on a PEMFC stack of 100W rated power; the orthogonal experiment method is adopted to analyze the influencing degree of the operational parameters on the electric efficiency and the optimal working condition. The results show that the effects of temperature, pressure,humidity and the coupling interaction between temperature and humidity are highly significant, and temperature is the most significant among them, the optimal working condition is obtained in the upper limit of the experimental range, namely, 60℃, 0.3MPa, 100% humidity. And then the conception of PEMFC-thermal engine is proposed through incorporating the characteristics of PEMFC and thermal engine. On studying the structural design of heat exchanger and the power matching design of PEMFC and thermal engine, an experimental setup for the CPHS of PEMFC-thermal engine was built up. The feasibility and the effect are experimentally studied. The experimental results show that the waste heat of the PEMFC stack can meet working demand of the thermal engine. The CPHS of PEMFC-thermal engine can output electric and mechanical energy, which enhanced the overall fuel efficiency by 58.5%.