Study on design parameters' effect on net water and power production from PEMFCs

Abstract

To overcome energy crisis in foreseeable future, human focused on clean and efficient energy source. Hydrogen fuel cells are recognized as typically clean energy source because there is no emission of harmful gas $(i.e. CO_2 and NO_x)$. Fuel cells can production power, and heat as well as water by electro-chemical reaction of hydrogen and oxygen. However, only power and heat is typically used and generated water is not considered for its use. Because 1kW proton exchange membrane fuel cell (PEMFC), which is applied to residential use, can generate 11.52 l/min of water, generated water may be used for drinking water. So, researches for investigating water balance of PEMFC and becoming combined water and power production (CWPP) system is needed. Water balance of PEMFC is comprised of input, output, generation, and accumulation in steady state. Input water is ionized water for membrane hydration, and generated water denotes theoretically produced water (11.52 l/day for 1 kW PEMFC). Accumulated water denotes the water to be isolated in fuel cells, not to discharge to outlets. Operation parameters such as inflow rate of reactants ($H_2$, and $O_2$), temperature, pressure, and relative humidity (RH) of reactants can affect input water and generated water. Design parameter such as cell design and channel design can have effect on generated and accumulated water. Because the ionized water is used for input water, the research for increasing generated water and increasing accumulated water is necessary for CWPP system. This means that effect of design parameter on fuel cell should be investigated and this research focused on it. For analysis of water balance in fuel cell, computational fluid dynamics (CFD) model was developed. This model is solved with simple electro-chemical reaction as well as governing equations. Power production of the model is verified by previous researches’data with I-V curve and water balance is verified by experimental data with RH of outlets. ...