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Hydrogen Purity and Fuel Cells


image of a fuel cell, in the context for measuring hydrogen quality and cleanliness

For hydrogen, as a fuel and gas, in order to be used, it must be clean and pure, thus hydrogen purity for fuel cells is a very important topic. Several factors affect hydrogen quality, such as the concentration of the hydrogen and the presence of contaminants which could be any molecules that are not hydrogen, such as nitrogen, water vapor, carbon monoxide, sulfur etc.


While hydrogen contaminants can originate from and/or be associated with multiple points of the hydrogen value chain, it also poses a special risk for fuel cells.

Why Do Hydrogen Quality Standards Exist?


Hydrogen purity standards exist for various applications. In the case of fuel cells, these standards exist in order to protect the integrity of the fuel cell and ultimately the end-consumer. Hydrogen quality is already defined by different standards, such as the ISO-14687. While some impurities may lead to decrease in efficiency, others may pose severe damage to the fuel cell, reversible or irreversible.


Due to this sensitivity, the effect that contaminants have on the fuel cell can be conceptualized into two categories:

  1. Diluting: non-damaging but diluting the hydrogen, leading to reduced fuel cell efficiency and poor performance.

  2. Damaging: Other impurities can lead to damage, including irreversible damage, which can deteriorate the fuel cell permanently over time.

According to the severity of the contaminant the maximum allowance level is defined by the ISO-14687.


ISO-14687: Hydrogen Purity Required for Fuel Cells


The reason why the standard is strict and the permissible concentrations are so low is because, as mentioned before, the current fuel cells are extremely sensitive to these impurities, with the emphasis that different types of fuel cells may be sensitive to different types of contaminants. For example, alkaline fuel cells are much more tolerable towards ammonia levels while this contaminant could be poisonous for PEM fuel cells even at low concentrations. Thus, the ISO is set to protect the fuel cells by ensuring the necessary quality of hydrogen fuel available at refueling stations.


The ISO-14687 hydrogen quality standard defines the maximum allowable impurity concentration of 13 impurities (gasses and VOCs) that are specifically important for fuel cells applications. The table here specifies the maximum allowable concentration in ppm of contaminants for fuel cells, either stationary or mobile.

Table describing the levels of the ISO-14687 for hydrogen quality for fuel cells

There are decision-makers from the industry that are responsible for setting these hydrogen purity standards and values, for updating the table periodically according to the actual use of hydrogen, reported incidence, updated production facilities and so on.


Monitoring Your Hydrogen Quality for Fuel Cells


The two main end users in the hydrogen supply chain that need to monitor hydrogen quality for fuel cells are:

  1. Fleet managers and fuel cell operators

  2. Hydrogen refueling stations operators

For H2-based transport and fuel cells, users like fleet managers and fuel cell operators need to confirm that the hydrogen being used is in compliance with ISO in order to keep their assets safe, efficient and performing optimally. These users periodically measure the quality of the hydrogen with lab tests, but since it is not frequent, this means they can risk contamination.


Also monitoring hydrogen quality is important for hydrogen refueling stations (HRSs) which have high liability towards the end-users. While most HRSs don’t produce the hydrogen on-site and have their supply from different sources, they still need to ensure that the hydrogen they provide to end-users is good to use. HRSs rely on periodic lab tests where the sampling poses an additional contamination-risk. Moreover testing could take time and requires lots of logistics associated with sampling and shipping hydrogen cylinders sometimes across borders.


Conclusion


When using hydrogen, it is important to ensure that the hydrogen purity required for fuel cells is being met. Thus, regularly monitoring to confirm that the hydrogen supply feeding the fuel cell is meeting quality standards is vital to protect the integrity of the fuel cell. Using NanoScent’s VOCID® H2Confirm allows users across the value chain to easily monitor critical contaminations in the hydrogen they use or produce thus ensuring efficient and effective use of the hydrogen. VOCID® H2Confirm can be integrated in-line and provide real time results eliminating the hassles related to hydrogen sampling and shipping.



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