Donaldson Filters Keep Fuel Cells Clean

The company’s products fight pollutants that can affect fuel-cell performance and the lifetime of the stack.

October 18, 2024

John Kendall

Donaldson offers a range of technologies that help keep fuel cells running properly. (Donaldson)

One of the advantages of the internal combustion engine is that it can function with relatively simple intake air filtration. Provided that dust is kept out, air entering the engine can ensure that the necessary combustion process takes place. So, a relatively simple dust filter will do the job.

Cathode air filters contain multiple layers to screen out sulphur dioxide, nitrogen oxides and ammonia. (Donaldson)

By comparison, hydrogen fuel cells are far more sensitive to air quality. Other pollutants can affect both fuel-cell performance and the lifetime of the fuel-cell stack. At the recent IAA Transportation Show in Hanover, Germany, Donaldson Filtration Solutions displayed tailored solutions through its range of cathode air filters. These typically rely on multiple layers – including activated carbon, an acid and base layer, and a dust filter – to screen out sulphur dioxide, nitrogen oxides and ammonia, while allowing for customization to protect against butane, toluene and other unwanted compounds.

Donaldson’s application development engineer Tim Billiau told SAE Media that one of its latest air filters for a hydrogen fuel-cell stack contains a pre-cleaner up front that can be serviced and provides dust filtration just like that on a diesel truck.

“Inside there are two separate elements. There’s a carbon pack for the fumes and then we even have two outlets,” Billiau explained. “For passenger cars you have the small fuel-cell stacks, low power. But for trucks and buses you need more, so that’s why we go for one big air cleaner and two outlets. One air cleaner can feed two fuel-cell stacks. To get to the correct power you can have two air cleaners, too, so on top you have the radial sealed, more conventional filter with a carbon pack also inside. It does the same thing with a two-stage air cleaner, it’s a round radial sealed air cleaner. We have also added a pre-cleaner with a two-stage air cleaner and a carbon pack inside and this is for those that give us one outlet.”

Since the carbon pack treats gaseous pollutants, it needs to be monitored to ensure that the outlet air is clean enough. The unit provides a warning for when the carbon pack needs to be replaced.

In terms of the layout, it’s a matter of how the customer wants to package it, Billiau said. They can opt for one filter per stack or a larger air cleaner that can feed two stacks. A sensor in each outlet for the dual-outlet model ensures a balanced airflow to the stacks.

Beyond fuel-cell filtration

Donaldson also displayed at IAA Transportation its range of humidifiers, water separators and coolant ion exchangers for fuel cells, as well as venting solutions for battery packs and fuel cells. The humidifiers ensure a high and stable level of humidity in the air supply by transferring humidity from the exhaust gas to the inlet air stream prior to entering the fuel cell. This provides optimal operating conditions for the ionomer, according to Donaldson.

The water separators ensure the intake air filters stay as dry as possible. Certain applications also require the discharge of liquid water from the tailpipe to be controlled.

High-pressure (<420 bar) and low-pressure (<25 bar) filters help protect fuel cells from contaminants that can affect performance and lifetime. (Donaldson)

The coolant ion exchangers help remove other contaminants that can come from within a PEM fuel cell itself. Ions from materials in the bipolar plates, radiators and other coolant circuit components can leach into the coolant. The exchangers work by capturing the ions on a special resin, ensuring the coolant remains non-conductive and maintains a low dielectric constant. A screen is integrated into the same housing to prevent larger particles from blocking the channels in the bipolar plates.

Donaldson’s Dual-Stage Jet, which launched earlier in 2024 at The Battery Show in Stuttgart, Germany, is its latest battery-venting solution. The company claims the technology offers the industry’s fastest degassing capabilities, at rates of approximately 100 L/s at 100 mbar. The medium-pressure solution features an intelligent poppet and cap design that can be jettisoned to produce a large opening for gas to escape in case of an emergency. During normal operation, pressure equalization is said to be consistent with minimum airflow of 97 L/hour at 10 mbar.

Though fuel cells operate within a sealed housing, they incorporate a membrane vent to allow the enclosure to breathe. Donaldson offers a high-pressure Dual-Stage Burst solution that enables a pressure relief of 25 L/s at 300 mbar after a series of pins pierce its Tetratex ePTFE membrane. Continuous pressure equalization during normal operating conditions sees minimum airflow of 17.8 L/hour at 10 mbar.