Waste Heat Recovery Of A PEMFC System By Using Organic Rankine Cycle

The proton exchange membrane fuel cell(PEMFC)is one of the most promising energy device for its inherently higher efficiency and much fewer emission-related issues than many other energy-conversion devices.The working temperature of PEMFC is strictly restricted between 60? to 80?.Almost 50% chemical energy is transferred to the environment by the waste heat,which indicates that there is a good potential in waste heat recovery,and cooling system with a high-heat transfer coefficient and temperature-balance ability is of great significance.However,the low working temperature of PEMFC makes it difficult to reuse the waste heat.In this study,two systems are brought forward to recover the waste heat of a proton exchange membrane fuel cell(PEMFC)to generate mechanic power,which are named the organic Rankine cycle(ORC),and heat pump(HP)combined organic Rankine cycle(HPORC).The cooling performance of both systems are also analyzed.Especially,we devoted into researches of theoretical thermodynamic analysis and system level simulation of ORC as well as HPORC to compare the thermal efficiency and net power.The influence of key factors is investigated,such as the evaporating temperature and condensing temperature in the ORC and HPORC.With R123,R245 fa,R134a,water,and ethanol being selected as the working fluid respectively,the optimum temperature and thermal efficiency is observed.As the evaporating process of ORC and HPORC absorbs heat fast,the cooling ability of ORC and HPORC is also investigated.Compared to the traditional cooling system of PEMFC,ORC and HPORC processes higher heat transfer coefficient and cause smaller temperature difference of PEMFC.The cooling plate of PEMFC cathode with different flow filed structure is calculated,according to which the original flow filed structure is improved.