Fuel cell development & testing by mass flow control

March 29, 2022 Jos Abbing

Supporting an energetic future

Fuel cells play an important role in our energy transition supporting an energetic future. They make it possible to transform hydrogen from renewable energy sources back to electricity. Mass flow control is a key factor in fuel cell development and testing, as fuel cells highly depend on fluidic parameters during testing.

In this blog I will explain how mass flow control contributes to this development focusing on the thermal-bypass technology for low density gases.

Mass flow control in renewable energy

Fuel cell development

A new fuel cell design depends on a lot of parameters. And to test it correctly, you need to know the properties and number of gaseous parameters, as accurately as possible. An important lesson I learned from a tricky school assignment, is that the final test result is never better than how precise your input is controlled.

Fuel cell test houses, universities and fuel cell test equipment manufacturers benefit from this basic knowledge when they use our flow control and measurement technology.

Why is mass flow control & measurement important?

For those of you who are not familiar with fuel cells, I start with some basics; For example, PEM-type fuel cells (Polymer Electrolyte Membrane), depend on executing an electrochemical process, amongst other types of fuel cells. Therefore, it can only supply electrical current when it receives the following fluids:

  • The anode needs optimal feed of humidified hydrogen
  • The cathode needs optimal feed of humidified oxygen, or air
This is preferably executed with optimal ‘stoichiometry’, which is a key factor for fuel cell efficiency.
Read here more about the role of flow control in producing hydrogen

Hydrogen Fuel Cell explained
PEM, Polymer Electrolyte Membrane Fuel Cell
Leak testing of fuel cell stacks
Leak testing of fuel cell stacks

The efficiency of the fuel cells depends on the composition and amount of humidified hydrogen and air, their flow speed, pressure conditions, and the pressure difference across membranes. The sweet spot for optimal performance is also influenced by external factors, such as the required electrical load together with ambient and fluid temperatures.

Another factor in play is the fuel cell design itself, and its attached parameters, such as membrane thickness, type of electrolyte, active electrode surface area, and the effectivity of gas diffusion layers.

Mass flow control in fuel cell testing

Below graph gives an indication of mass flow control instruments as seen in test-setups. It shows where you can apply our mass flow instruments. To keep it simple: The flow meters and pressure instruments take care of the main liquid-, gas- and pressure- measurement and control related tasks.You can clearly see the fluidic dependencies and interactions.

Represented evaporator unit (CEM) - mass flow control in fuel cell testing
The represented Controlled Evaporator Mixer is typically used for low flow and low humidification levels. For higher flows we often advise towards cascaded systems.

Reasons to use mass flow control

The result of any test, is as good as the sum of accuracies

Please consider that all fluidic control & measurand dependencies always interact simultaneously. Knowing this, you can understand that these have a major influence on functional tests and stress tests, for both single cells and fuel cell stacks. Many test goals for fuel cells or for fuel-treating systems are affected by this; for example, when determining performance indicators and characterisations (according to IEC 62282-series or other standards). The realised input feed control accuracy can have a huge impact on your systematic uncertainty.

Mass Flow Controllers for ‘high’ flows
Mass Flow Controllers for ‘high’ flows; for testing and high power- or commercial use

The best choice to control your fuel cell related- flow, pressure and density conditions are devices based on a thermal bypass mass flow measuring technology. A mass flow controller based on this principle can achieve the most flexible, accurate and repeatable fluidic control, including:

  • Reliable control with fast on-board (direct valve) PID control
  • Instant mass-based measurement (no volume and P+T based conversions to mass)
  • Higher systematic accuracy for fluidic control & measurement
  • More flexible mix & ratio feed control for H2/N2/H2O and O2/H2O and other gases
  • Independent anode and cathode flow speed- and pressure control
  • Better support for profile switching or characteristics change for load change, durability cycling, polarization, purging, etc.

From single cell to large set-ups (High flow)

Bronkhorst can supply instruments to support setups for a single cell stack up to stacks of 100’s of kilowatts. Our products (like the IN-FLOW ‘High-FLOW’ F-117DI series) are used for testing and for high power use or commercial use, which require wider load dynamics or highest durability.
We have mass flow control instruments available for OEM applications, laboratory applications as well as industrial versions. Check out our IN-FLOW ‘High-FLOW’ series. In case multiple gaseous fuels are used, products support on-board multi-fluid configuration.

Do you want to learn more about our product portfolio for renewable energy?

Check our renewable energy page.

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