Microfluidic hydrogen fuel cell flow regulation

Microfluidic hydrogen fuel cell flow regulation

Discussing hydrogen fuel cell research

Hydrogen fuel cells are an attractive portable power source, providing electrical energy storage orders of magnitude greater than similarly sized batteries. Due to expanding investments in the future of hydrogen, such as the new incentives for hydrogen production enumerated in the Inflation Reduction Act, the hydrogen fuel cell market is expected to grow significantly in upcoming years. Some key focus areas for research and development in the fuel cell market include:

  • Increasing the durability and reliability of fuel cells
  • Reducing fuel cell cost
  • Increasing fuel cell efficiency
  • Improving operating conditions

Many types of hydrogen fuel cells have been developed with various positive and negative attributes. For example, proton exchange membrane fuel cells (PEMFCs), probably the most widely used fuel cell type, have advantages of high power density and long operating life but disadvantages of high cost and high operating temperature. The following list highlights the most common types of fuel cells as well as their main advantages and disadvantages:

Fuel Cell Type Advantages Disadvantages
Proton Exchange Membrane (PEMFC) -Commonly used

-High power density

-Long operating range

-High operating temperatures

-Expensive

-Intolerant to CO

Direct Methanol (DMFC) -Less complex design -Requires noble catalyst
Alkaline (AFC) -Inexpensive

-Tolerant of CO

-Uses corrosive electrolyte

-Intolerant of CO2

Phosphoric Acid Fuel Cell (PAFC) -Widely available -Short operating time
Molten Carbonate (MCFC) -High efficiency  

-Electrolyte instability

-CO2 poisoning

Solid Oxide (SOFC) -High efficiency  

-High operating temperatures

-Expensive

Introducing microfluidic fuel cells

In microelectronics, an exciting fuel cell technology is the microfluidic fuel cell, also called a membraneless laminar flow-based fuel cell (LFFC). In this type of fuel cell, microchannels of laminar flow are used to separate anode, cathode, and electrolyte sections. In this system, an electrolyte stream enters the fuel cell as an aqueous solution, running parallel to a fuel anode stream such as hydrogen and oxidant cathode stream such as oxygen, avoiding any turbulent mixing and allowing for electricity to be generated.

Due to physical limitations, LFFCs can only be used to power microelectronics and are primarily used for military and government applications. However, microfluidic fuel cells also serve an additional purpose in that they can be modified to characterize the performance and durability of various types of electrodes and catalysts, allowing for the optimization of various types of fuel cells such as those mentioned previously.

In the following, we discuss how Alicat’s CODA KC-Series mass flow controllers improve microfluidic membraneless laminar flow hydrogen fuel cells using precise, repeatable, and accurate low flow regulation.

Designing microfluidic hydrogen fuel cells

In an experimental setup, a cost effective, simple design for a microfluidic hydrogen fuel cell includes acrylic microfluidic flow chambers for H2 and O2 solutions as well as an acrylic microfluidic flow chamber for a liquid electrolyte solution, such as H2SO4. Between these different layers are gas diffusion electrodes made using conductive (Pt) carbon paper. Additionally, two 1-mm-thick graphite windows act as current collectors. Mass flow controllers regulate the flow of the H2, O2, and electrolyte solutions, ensuring that constant laminar flow is maintained at all times.

Using Alicat’s CODA KC-Series for microfluidic fuel cells

Since the microfluidic fuel cell depends on repeatable, accurate, non-turbulent, laminar flow control to properly separate the anode, cathode, and electrolyte microchannels, an extremely precise, low flow mass flow controller is ideal. Alicat’s CODA KC-Series mass flow controller regulates flow at extremely low flow rates to help researchers find ideal operating conditions. The CODA KC-Series allows for continuous, precise, repeatable automation of the microfluidic fuel cell, including the following benefits and specifications:

  • NIST-traceable liquid accuracy of ±0.2% of reading or ±0.05% of full scale, whichever is greater
  • NIST-traceable gas accuracy of ±0.5% of reading or ±0.05% of full scale, whichever is greater
  • Full scale range down to 40 g/h with a control range of 2%-100% of full scale, allowing for flow control down to .0133333 g/min
  • Response times as fast as 500 ms
  • Repeatability of ±0.05% of reading or ±0.025% of full scale, whichever is greater
  • Compatibility with a wide range of aggressive gases and liquids, allowing for custom fuel, oxidant, and electrolyte testing
  • Resistance to external vibrations, mitigating environmental process disturbances

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