September 2004

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WEST SACRAMENTO, CA - Current garage designs are likely to be safe to house and service future hydrogen fuel cell (HFCVs) and hydrogen i.c. vehicles without modifications, according to a 2-year study commissioned by the California Fuel Cell Partnership (CaFCP).

This is the gist and bottom line of the 80-page report, “Support Facilities for Hydrogen-Fueled Vehicles,” produced by Parsons Brinkerhoff, Pasadena, CA, a 100-year-old global construction planning and management firm. It was produced in cooperation with hydrogen safety expert Dr. Michael Swain, University of Miami, whose experience goes back to the early 1980s, and Tiax, a Cambridge, MA-based r&d company and successor to Arthur D. Little which has been working in hydrogen for many years as well.

CaFCP executive director Catherine Dunwoody said it’s vital to understand how current design and construction practices relate to hydrogen fuel cell vehicles and fueling stations as they begin to come into use. “It is encouraging to know that current standards, coupled with the preventive measures taken by the manufacturers, point to safe facilities without costly modifications,” Dunwoody added.

The team developed case studies for several facility types: commercial multi-story garages both above and below ground; commercial maintenance and repair service stations, and residential two-car garages. For each type, a baseline building design was developed that incorporated functional requirements and applicable building codes. The authors emphasized comparisons to current codes for facilities designed to house compressed natural gas vehicles to find out what extra steps would be needed to accommodated hydrogen vehicles.

Hydrogen Flow is Limited, Diluted

The model scenarios showed that in all cases, leaking hydrogen did not extend beyond two feet immediately around the vehicle. Typical airflow, from natural or mechanical ventilation, resulted in diluting leaking hydrogen to lower than the lowest flammable concentration levels, according to a summary of the report.

Since there were no experimental or pre-prototype hydrogen fuel cell vehicles available for real-life tests for this project, the authors based their study on the characteristics of a hypothetical five-passenger sedan with a 6 kg compressed hydrogen gas storage tank. The vehicle was assumed to comply with SAE J2575 and J2579 standards for hydrogen and fuel cells which provide for safety mechanisms onboard designed to detect and limit the amount of leaked hydrogen under certain conditions.

Each detector would be designed to signal a procedure that would shut down hydrogen and isolate the tank when it detects 1% of hydrogen in the air. Another mechanism would include an on-board computer capable of shutting down hydrogen after it receives a signal indicating a flow leak of more than 20 cubic feet/minute when the vehicle is at rest. Another assumption was that the vehicle comes equipped with a valve that isolates hydrogen in the tank when the fuel cell engine is shut down.

The summary cautions the results should be seen in the context of pre-commercialization of fuel cell vehicles and still-developing codes, standards and other regulatory approaches, but “the results nonetheless suggest that facilities compliant with today’s requirements could safely accommodate HFCVs without any modification.” The summary also emphasized that one of the most important safety aspects will consist of “preventive measures integrated into the vehicles themselves, such as leak sensors and shut-off valves.”

The study is available on the Partnership’s website, www.cafcp.org. Contact: Bob Hayden, 415/381-7225.