Allengra’s Hydrogen Flow Meter for Controlling Anode Recirculation in PEM Fuel Cells

May 27, 2024, 3770 minute read

Allengra's Hydrogen Flow Meter on a table with laboratory equipment

PEM fuel cells – Polymer Electrolyte Membrane fuel cells – are highly efficient and are found across a wide variety of types and applications, from automotive to stationary power generation. These systems are fundamentally simple; they convert the highly flammable gas of hydrogen and oxygen into electricity, with water as their only byproduct.

With the reactants such as hydrogen coming in and products such as water coming out, all that’s left in between is electricity. But important as they are, hydrogen and oxygen don’t cross paths and react by themselves; like most chemical reactions, they require some assistance, and that help comes from the fuel cell’s anode and cathode compartments.

Hydration and Anode Circulation in PEM Fuel Cells 

The main purpose for anode circulation in PEM fuel cells is to optimize the performance and water balance, ensuring that the hydrogen flowing into the fuel cell stack is used as efficiently as possible. To ensure an even distribution of hydrogen throughout the stack, there is an abundance of hydrogen.

The anode gas from the stack outlet can be recirculated back to the stack inlet. This process saves the excess hydrogen from being unnecessarily wasted, thereby increasing the efficiency of the fuel cell, as there is more hydrogen available for the electrochemical reaction.

Nitrogen Cross-Over in PEM Fuel Cells

A challenge for PEM fuel cells is the cross-over of nitrogen from the cathode to the anode compartment, that can lead to the anode outlet gas being increasingly enriched with nitrogen.

Too much nitrogen on the anode side of the fuel cell tends to be destructive. High levels of nitrogen in place of hydrogen cause the fuel mix to be less efficient, making the electrochemical reactions less powerful and in some cases, may cause the fuel cell to degrade.

This nitrogen accumulation is neutralized by so-called purge cycles, where the anode gas is blown out from the stacks for a short period of time to reduce the nitrogen content and restore the balance. It is essential to have a healthy balance in this mixture, but so are other variables such as hydration levels and pressure to avoid any other degradation factors that may arise.

Allengra’s Hydrogen Flow Meter Comes to the Rescue

Our Hydrogen Flow Meter combines cutting-edge ultrasonic sensor technology with real-time data analysis, tackling these issues with these measuring capabilities:

Density and Mass Flow

It’s a real selling point that Allengra’s flow meter can measure both mass flow and gas concentration accurately with the ratio of hydrogen/nitrogen staying in the optimal zone, increasing the efficiency and lifespan.

Volume Flow, Temperature, Humidity and Pressure

All this data courtesy of the sensor’s interface, can be obtained in real-time and used to keep the various parameters of the anode recirculation process within the desired ranges. Meanwhile, the humidity monitoring contributes to hydrogenation of the polymer electrolyte membrane, that ensures an efficient proton conduction. 

Ideal Hydrogen/Nitrogen Ratio

This flow meter reads the concentrations levels of hydrogen and nitrogen, providing crucial information that allows the sweet-spot ratio to be found, which immensely contributes to the fuel cell stack to its best performance and longest service time.

A Cost-Efficient Automotive Solution

This Hydrogen Flow Meter is tailored for seamless integration with a compact design, along with a CAN bus interface, being the ideal candidate for fuel cell applications and not only!