Learning Forum

[Hasan Celik]

Hello,

I am developing a three-dimensional, four-cell anion-exchange-membrane/alkaline water-electrolyzer stack model in Ansys Fluent 2026 R1. I would appreciate guidance regarding the correct electrical configuration of a true bipolar stack.

I am using:

• Potential/Electrochemistry
• Electrolysis and H₂ Pump Model / Electrochemical Devices
• Device type: Alkaline Electrolysis
• Multiphase formulation
• Resolved MEA-layer modelling
• Butler–Volmer electrochemical kinetics
• 1 M KOH electrolyte
• Operating temperature: approximately 333 K
• Operating pressure: 1 atm

Each of the four cells contains separate zones for:

• Anode current collector
• Anode flow channel
• Anode porous transport layer/GDL
• Anode catalyst layer
• Membrane
• Cathode catalyst layer
• Cathode porous transport layer/GDL
• Cathode flow channel
• Cathode current collector

The individual cells are intended to be connected electrically in series through bipolar connections:

• Cell 1 cathode current collector ↔ Cell 2 anode current collector
• Cell 2 cathode current collector ↔ Cell 3 anode current collector
• Cell 3 cathode current collector ↔ Cell 4 anode current collector

Only the two external surfaces are defined as the stack terminals:

• External anode terminal
• External cathode terminal

The intended total stack voltage is initially 6 V, corresponding to approximately 1.5 V per cell.

 

 

The contact zones are named:

bp12_contact
bp23_contact
bp34_contact

 

However, Fluent repeatedly gives warnings such as:

 

Warning: Anode side is electrically connected with cathode side
(cell2_anode_cc and cell1_cathode_cc)!

Warning: Anode side is electrically connected with cathode side
(cell3_anode_cc and cell2_cathode_cc)!

Warning: Anode side is electrically connected with cathode side
(cell4_anode_cc and cell3_cathode_cc)!

After that I have defined the boundry condtions and started to solve. 

The solution later becomes unstable and produces nonphysical currents and floating-point errors.

Could you please clarify:

1. Does the resolved Alkaline Electrolysis model support a true multi-cell bipolar stack?
2. Are these electrical-connection warnings expected for series-connected cells?
3. How should the bipolar interfaces be defined?
4. Should I apply the total stack voltage, for example 6 V, or the individual cell voltage, for example 1.5 V?
5. Is there any Fluent stack tutorial or example available?

Sincerly,