Fuel cells are highly sensitive to impurities, which can have several negative effects. Even trace levels of contaminants like moisture (H₂O), oxygen (O₂), nitrogen (N₂), or carbon monoxide (CO) can suppress the efficiency of conversion, leading to reduced power output.
Over time, these contaminants can also damage the fuel cell components, particularly the catalyst, which can lead to costly repairs or replacements.
Maintaining purity is especially crucial in ISO 14687-compliant fuel cells, which specify strict limits on the concentration of impurities such as H₂O, O₂, and N₂.
The exact nature and level of impurities can vary depending on the source of hydrogen—whether from Steam Methane Reforming (SMR), pyrolysis, or electrolysis.
Each method of hydrogen production may introduce different contaminants that need to be monitored and controlled before the hydrogen enters the fuel cell.
Key Purity Measurements in Hydrogen for Fuel Cells
Several key purity measurements are critical to ensuring that hydrogen used in fuel cells meets the necessary standards for high performance:
1. Moisture (Water Vapor) in Hydrogen:
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Excess moisture can interfere with the electrochemical reactions inside the fuel cell, leading to decreased efficiency and potential damage to the fuel cell’s components. Monitoring moisture levels is critical to ensure the hydrogen stream is dry enough to maintain optimal fuel cell performance.
2. Oxygen in Hydrogen:
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Oxygen contamination can lead to reduced power output and efficiency of the fuel cell. Even small amounts of oxygen can cause significant degradation of the fuel cell’s performance over time. Continuous monitoring of oxygen levels ensures that the hydrogen remains free of this harmful contaminant.
3. Carbon Monoxide (CO):
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Carbon monoxide is one of the most harmful contaminants for fuel cells, particularly PEM fuel cells. CO can adsorb onto the platinum catalyst, reducing its ability to facilitate the hydrogen-oxygen reaction. Even trace amounts of CO can drastically lower the performance and lifespan of a fuel cell. Monitoring CO levels is essential to avoid catalyst poisoning.
4. Hydrogen Purity Levels:
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The overall purity of hydrogen must meet stringent standards, such as those defined in ISO 14687, which sets guidelines for acceptable contaminant levels in hydrogen used for fuel cells. Continuous monitoring of hydrogen purity ensures the hydrogen meets these standards, preventing performance loss and maximizing fuel cell efficiency.
Additional Safety Considerations: Installation and Package Integrity
Apart from purity concerns, specific installation safety and system integrity measures are crucial for hydrogen storage and distribution in fuel cell systems. Leak detection systems are necessary to identify any leaks in the hydrogen supply, which can present serious safety risks. Additionally, inerting—the process of adding an inert gas to reduce the risk of combustion—can be used to safeguard the system from unintended ignition events.
What Types of Analyzers Are Used for Hydrogen Purity in Fuel Cells?
To maintain hydrogen purity at the necessary levels for fuel cell operation, a variety of advanced analyzers are employed to detect and remove contaminants before hydrogen enters the fuel cell.
