United States

In any application involving the production storage or use of hydrogen sensors are important devices for alerting to the presence of leaked hydrogen. Hydrogen sensors should be accurate sensitive and specific as well as resistant to long term drift and varying environmental conditions. Furthermore as an integral element in a safety system sensor performance should not be compromised by operational parameters. For example safety sensors may be required to operate at reduced oxygen levels relative to air. In this work we evaluate and compare a number of sensor technologies in terms of their ability to detect hydrogen under conditions of varying oxygen concentration.

A properly trained first responder community is critical to the successful introduction of hydrogen fuel cell applications and their transformation in how we use energy. Providing resources with accurate information and current knowledge is essential to the delivery of effective hydrogen and fuel cell-related first responder training. The California Fuel Cell Partnership and the Pacific Northwest National Laboratory have over 15 years of experience in developing and delivering hydrogen safety-related first responder training materials and programs. A National Hydrogen and Fuel Cell Emergency Response Training Resource was recently released. This training resource serves the delivery of a variety of training regimens. Associated materials are adaptable for different training formats ranging from high-level overview presentations to more comprehensive classroom training. This paper presents what has been learned from the development and delivery of hydrogen safety-related first responder training programs (online classroom hands-on) by the respective organizations. The collaborative strategy being developed for enhancing training materials and methods for greater accessibility based on stakeholder input will be discussed.

Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refuelling operations. Based on industry stakeholder input conducted experiments were devised to assess the utility of modelling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International's Corral Hollow Test Site. Moreover the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modelling approaches.

Sandia National Laboratories has worked with stakeholders and original equipment manufacturers (OEMs) to develop scientific data that can be used to create risk-informed hydrogen codes and standards for the safe operation of indoor hydrogen fuel-cell forklifts. An important issue is the possibility of an accident inside a warehouse or other enclosed space where a release of hydrogen from the high-pressure gaseous storage tank could occur. For such scenarios computational fluid dynamics (CFD) simulations have been used to model the release and dispersion of gaseous hydrogen from the vehicle and to study the behavior of the ignitable hydrogen cloud inside the warehouse or enclosure. The overpressure arising as a result of ignition and subsequent deflagration of the hydrogen cloud within the warehouse has been studied for different ignition delay times and ignition locations. Both ventilated and unventilated warehouses have been considered in the analysis. Experiments have been performed in a scaled warehouse test facility and compared with simulations to validate the results of the computational analysis.

Performing research in the interest of providing relevant safety requirements is a valuable and essential endeavor but translating research results into enforceable requirements adopted into codes and standards a process sometimes referred to as codification can be a separate and challenging task. This paper discusses the process utilized to successfully translate research results related to bulk gaseous hydrogen storage separation (or stand-off) distances into code requirements in NFPA 55:Storage Use and Handling of Compressed Gases and Cryogenic Fluids in Portable and StationaryContainers Cylinders and Tanks and NFPA 2: Hydrogen Technologies. The process utilized can besummarized as follows: First the technical committees for the documents to be revised were engaged to confirm that the codification process was endorsed by the committee. Then a sub-committee referred to as a task group was formed. A chair must be elected or appointed. The chair should be a generalist with code enforcement or application experience. The task group was populated with several voting members of each technical committee. By having voting members as part of the task group the group becomes empowered and uniquely different from any other code proposal generating body. The task group was also populated with technical experts as needed but primarily the experts needed are the researchers involved. Once properly populated and empowered the task group must actively engage its members. The researchers must educate the code makers on the methods and limitations of their work and the code makers must take the research results and fill the gaps as needed to build consensus and create enforceable code language and generate a code change proposal that will be accepted. While this process seems simple there are pitfalls along the way that can impede or nullify the desired end result – changes to codes and standards. A few of these pitfalls include: wrong task group membership task group not empowered task group not supported in-person meetings not possible consensus not achieved. This paper focuses on the process used and how pitfalls can be avoided for future efforts.

Experiments were conducted to assess detectability of a low-level leak of hydrogen gas and the uniformity of hydrogen concentration at selected sensor placement locations in a realistic setting. A 5%2hydrogen/95%2nitrogen gas mixture was injected at a rate of 350 L/min for about 3/4 hour into a 93m3 residential garage space through a 0.09 m2 square open-top dispersion box located on the floor. Calibrated catalytic sensors were placed on ceiling and wall locations and the sensors detected hydrogen early in the release and continued to measure concentrations to peak and diminishing levels. Experiments were conducted with and without a car parked over the dispersion box. The results show that a car positioned over the dispersion box tends to promote dilution of the hydrogen cause a longer time for locations to reach a fixed threshold and produce lower peak concentrations than with no car present.

The Department of Energy the Department of Defense's Defense Logistics Agency and the Department of Transportation's Federal Transit Administration have funded learning demonstrations and early market deployments to provide insight into applications of hydrogen technologies on the road in the warehouse and as stationary power. NREL's analyses validate the technology in real-world applications reveal the status of the technology and facilitate the development of hydrogen and fuel cell technologies manufacturing and operations. This paper presents the maintenance safety and operation data of fuel cells in multiple applications with the reported incidents near misses and frequencies. NREL has analyzed records of more than 225000 kilograms of hydrogen that have been dispensed through more than 108000 hydrogen fills with an excellent safety record.

There are times in engineering when it seems that safety and equipment cost reduction are conflicting priorities. This could be the case for pressure relief valves and vent stack sizing. This paper explores the role that component availability (particularly variety in flow and orifice diameters) plays in the engineer’s decision of a relief valve. This paper outlines the guidelines and assumptions in sizing and selecting pressure relief devices (PRDs) found in a typical high pressure hydrogen fueling station. It also provides steps in sizing the station common vent stack where the discharge gas is to be routed to prior being released into the atmosphere. This paper also explores the component availability landscape for hydrogen station designers and identifies opportunities for improvement in the supply chain of components as hydrogen fueling stations increase in number and size. American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section VIII (ASME BPVC Section VIII) Compressed Gas Association S-1.3 (CGA S-1.3) and American Petroleum Institute 520 (API 520) standards provide specific design criteria for hydrogen pressure relief valves. Results of these calculations do not match the available components. The available safety relief valves are 50 to 87 times larger than the required calculated flow capacities. Selecting a significantly oversized safety relief valve affects the vent stack design as the stack design requires sizing relative to the actual flowrate of the safety relief valve. The effect on the vent stack size in turn negatively affects site safety radiation threshold set back distances.

The Hydrogen Safety Panel brings a broad cross-section of expertise from the industrial government and academic sectors to help advise the U.S. Department of Energy's (DOE) Fuel Cell Technologies Office through its work in hydrogen safety codes and standards. The Panel's initiatives in reviewing safety plans conducting safety evaluations identifying safety-related technical data gaps and supporting safety knowledge tools and databases cover the gamut from research and development to demonstration. The Panel's recent work has focused on the safe deployment of hydrogen and fuel cell systems in support of DOE efforts to accelerate fuel cell commercialization in early market applications: vehicle refuelling material handling equipment backup power for warehouses and telecommunication sites and portable power devices. This paper summarizes the work and learnings from the Panel's early efforts the transition to its current focus and the outcomes and conclusions from recent work on the deployment of hydrogen and fuel cell systems.

We are going to focus our discussion on “Explosions” its definitions from a scientific regulatory and societal perspective. We will point out that as defined these definitions are not consistent and lead to ambiguity. Of particular interest to this work is how this current ambiguity affects the emerging Regulation Codes and Standards (RCS) as applied to hydrogen technologies. While this manuscript has its roots in combustion science with extension to both the standard development and regulatory communities for hazards at large the unique behavior of hydrogen in many configurations motivates examining the relevant definitions and language used in these communities. We will point out the ambiguities how this leads to confusion in supporting definitions and how it leads to overly restrictive RCS for hydrogen applications. We will then suggest terminology which is not ambiguous internally self-consistent and allows appropriate RCS to be promulgated to ensure the safety of the public and capital to ensure the correct response of first responders and allow cost effective development of hydrogen technologies in our infrastructure.