Modeling the performance of hydrogen–oxygen unitized regenerative proton exchange membrane fuel cells for energy storage

et al. 2018

Int J Energy Res

Summary With the occurrence of reversible electrochemical reactions, mode switching considerably affects the electric performance of unitized regenerative fuel cells (URFCs) owing to the complicated mass and heat transfer. Although limited researches have been done, no such studies on mass and heat transfer through a three‐dimensional view are envisioned during mode switching. A three‐dimensional full‐cell model was developed and validated to study the dynamic characteristics of a proton exchange membrane‐based URFC during mode switching. Mode switching was performed by changing operation voltage from 0.60 to 1.65 V. Results showed that species and heat transfer affect the electric performance of the cell during mode switching, especially through the third dimensional. Local water starvation occurs on oxygen side catalyst layer and thus results in slight reduction on current density and hydrogen generation. Restricted to heat transfer capacity through ribs, heat transfer process adds total response time in URFCs. Heat flux and surface heat transfer coefficient are forecasted on the hydrogen and oxygen sides. A total time of 4 seconds is essential for URFC reaching a new relative balanced state.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat and mass transfer in a unitized regenerative fuel cell during mode switching

et al. 2018

Int J Energy Res

“…However, studies on the numerical simulation of URFC are few. The current work presents four studies on theoretical model and system performance models [9][10][11][12] and five studies on mass and heat transfer during mode switching [13][14][15][16][17] . Ito et al 13 built a gas purge model to predict the relationship of high-frequency resistance with purge flow rates and verified the prediction with the experimental results.…”

Section: Introductionmentioning

confidence: 99%

Mass transfer and cell performance of a unitized regenerative fuel cell with nonuniform depth channel in oxygen‐side flow field

Jia

et al. 2019

Int J Energy Res

Summary In this study, the cell performance of nonuniform depth and conventional straight channel in a unitized regenerative fuel cell (URFC) is compared. Various shapes of oxygen‐side channel cases are also proposed. Several parameters, such as the distribution of reactants and products and current density and powers in fuel cell (FC) and electrolytic cell (EC) modes, are investigated. A steady‐state model of two‐dimensional, two‐phase, nonisothermal, and coupled electrochemical reaction is developed. Five oxygen‐side channel shapes are also designed, in which the depth along the flow direction is narrowed. Result shows that narrowing the average channel depth can promote and guide the reactant transfer to the catalyst layer and avoid the blocking of the production. Thus, in comparison with the conventional channel, the cell performances of nonuniform depth and shallow straight channel cases are improved in both modes. In addition, with the decrease of average channel depth, the temperature uniformity gets better, which is also conductive to the improvement of cell performance. Furthermore, in FC mode at low voltage and EC mode, the cell net power basically increases with the decrease of the average channel depth ratio. And when the average channel depth is the same, the net power of straight channel is always lower than nonuniform depth case. This study introduces the round‐trip energy efficiency as an evaluation indicator of URFC. This efficiency can be increased by improving the cell performance of both modes, especially at high current density.

“…URFCs are used extensively, not only for space or military applications, but also for solar-powered aircraft, satellites, and micro-spacecraft applications [5][6][7]. Proton exchange membrane (PEM) is a convenient electrolyte technology for both WEs and FCs, as it allows for low operational temperature, quick start, fast response, high power and energy densities [8].…”

Section: Introductionmentioning

confidence: 99%

“…The literature on modeling of PEM URFC is extremely limited and very few articles have been published. Guarnieri et al [8] presented a performance model of a PEM URFC via providing voltage, power, and efficiency under varying load conditions as functions of the controlling physical quantities: temperature, pressure, concentration, and humidification. The model was used as a tool for investigating optimized cell/stack designs and operational conditions.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Simulation of Mass Transfer in Unitized Regenerative Fuel Cells under Operation Mode Switching

Wang

et al. 2016

Energies

Abstract:A two-dimensional, single-phase, isothermal, multicomponent, transient model is built to investigate the transport phenomena in unitized regenerative fuel cells (URFCs) under the condition of switching from the fuel cell (FC) mode to the water electrolysis (WE) mode. The model is coupled with an electrochemical reaction. The proton exchange membrane (PEM) is selected as the solid electrolyte of the URFC. The work is motivated by the need to elucidate the complex mass transfer and electrochemical process under operation mode switching in order to improve the performance of PEM URFC. A set of governing equations, including conservation of mass, momentum, species, and charge, are considered. These equations are solved by the finite element method. The simulation results indicate the distributions of hydrogen, oxygen, water mass fraction, and electrolyte potential response to the transient phenomena via saltation under operation mode switching. The hydrogen mass fraction gradients are smaller than the oxygen mass fraction gradients. The average mass fractions of the reactants (oxygen and hydrogen) and product (water) exhibit evident differences between each layer in the steady state of the FC mode. By contrast, the average mass fractions of the reactant (water) and products (oxygen and hydrogen) exhibit only slight differences between each layer in the steady state of the WE mode. Under either the FC mode or the WE mode, the duration of the transient state is only approximately 0.2 s.