Hydrogen Fuel Quality Update Karen Hall, Fuel Cell and Hydrogen Energy Association
The performance and durability of Proton Exchange Membrane (PEM) fuel cells is affected by the quality of the hydrogen fuel. The methods used to produce and purify hydrogen may result in different kind of impurities.
In order to ensure the appropriate standards and regulations are in place to facilitate wide-scale commercialization, there are a number of domestic and international efforts taking place to quantify the upper limits on potential impurities and define measurement techniques for verifying the quality specifications are met. This article highlights just a few of these key efforts.
Domestically, SAE J2719 is a published document that covers the hydrogen fuel quality requirements for PEM fuel cell vehicles. This means that there is now an ANSI-approved hydrogen fuel quality standard for fuel cell vehicles. The document is now available on the SAE website at http://www.sae.org.
There is also ongoing work on the development of commercial hydrogen measurement standards to meet the U.S. weights and measures requirements for commercial sale of hydrogen fuel. It is important to note that the hydrogen fuel quality specifications, as well as the test methods described in the developing standards, are expected to change as ongoing research and real-world demonstration projects help inform the process.
One European-led collaborative research project, "HyQ", is focused on pre-normative studies to provide a strong support to Regulation Codes and Standards organizations in order to normalize an acceptable fuel quality for PEM fuel cells. This project focuses mainly on transport applications but will also deal with stationary applications. Hydrogen fuel quality standards are essential for the mass commercialization of hydrogen based energy technologies.
There are three activities relating to hydrogen fuel quality within ISO/TC 197. The original document, ISO 14687, had a scope intended to cover all applications. However, experts recognized that the grades of fuel described in this document were not suitable for proton exchange membrane (PEM) fuel cells and a new work item proposal was developed to create a grade suitable for PEM fuel cell vehicles. This resulted in a change in scope for ISO 14687 and a Corrigendum was published as follows: ISO 14687-1:1999/ Cor. 1:2001/Cor. 2:2008 Hydrogen fuel - Product specification -Part 1: All applications except proton exchange membrane (PEM) fuel cells for road vehicles.
A Technical Specification (ISO TC 14687-2) was then developed and published to cover hydrogen quality for PEM fuel cells for road vehicles. That activity progressed to develop an International Standard. ISO 14687-2Hydrogen Fuel -Product Specification - Part 2: Proton exchange membrane (PEM) fuel cell applications for road vehicles.
An effort to address a related issue for hydrogen quality for PEM fuel cells for stationary applications was also initiated. This will produce ISO 14687-3Hydrogen Fuel - Product Specification - Part 3: Proton exchange membrane (PEM) fuel cell applications for stationary appliances. This is being addressed by Working Group 14, which held their kick-off meeting in March 2010, and now has a Draft International Standard out for comment and vote. Publication of this document will require a further change in scope to ISO 14687-1.
There is a desire to avoid requiring the same fuel to undergo separate testing to verify it complies with more than one resulting hydrogen fuel grade. After all, if the fuel complies with the most stringent grade, why undergo additional testing to allow use in less stringent applications?
The hydrogen fuel must be suitable for the technology that will use the hydrogen. Should testing take into account the hydrogen production method when a single source for the hydrogen is used? Does it make sense to test for constituents that cannot be present? Can and should fuel quality be validated taking both the end use and the fuel production and delivery methods into account?
Both WG 12 and WG 14 attempted to address this issue by including language that allows the buyer and seller to agree provisions that might, for example, waive testing for constituents that could not be present based on production method and storage techniques. Unfortunately, this key language was removed during recent editing and may be a cause for concern for ultimate approval of the ISO documents.
There is a desire by the ISO/TC 197 experts to consider the merits of having all grades of hydrogen in a single document ultimately, once the various unique cases are well-defined.
WG 14 agreed to harmonize ISO DIS 14687-3 with ISO 14687-2 as much as practical. It was noted that the hydrogen supply methods for stationary applications will be different than for hydrogen refueling stations. In addition, cycle times and anticipated system lifetimes will be different for the two applications. Therefore the constituent limits and method of testing fuel quality would need to be different between stationary applications and vehicle refueling.
The WG 14 recognizes that the hydrogen supply for stationary applications may include reformate, hydrogen produced following pressure swing absorption (PSA) of reformate, and hydrogen produced from electrolysis. Therefore ISO DIS 14687-3 takes the feedstock for the stationary fuel cell system into account.
An appropriate boundary point must be defined where the hydrogen quality sample will be taken. This will be between the final production and the fuel cell, and will relate to the stationary fuel cell system.
The ISO DIS 14687-3 presently addresses pipeline hydrogen. Once this part is published, WG 14 may then consider hydrogen cylinder (remote power) applications.