Article   |   Kees van Wingerden   |   18.02.2022

Hydrogen Safety

The recent COP 26 UN Climate Change Conference held in Glasgow once more highlighted the challenges the world is facing with respect to global warming. Four-fifths of the world's energy supply comes from the combustion of fossil fuels, resulting in the emission of significant greenhouse gases and especially CO2. In addition, Governments worldwide have released “hydrogen roadmaps” and committed more than EUR 60 billion in public funding while industry experts have announced ambitious plans with a total investment exceeding EUR 260 billion through 2030.

Establishing a hydrogen economy to replace a large proportion of fossil fuels, will play an important role in the journey to a decarbonised energy sector. Hydrogen only emits water when burned and therefore does not contribute to global warming to the same extent the combustion of fossil fuels does.

Projects that are about to start, or already underway, include green hydrogen production facilities; use of hydrogen domestically, mixing it with natural gas, and creating an infrastructure of hydrogen fueling stations.

Several studies performed in Australia, Europe and Japan show a more positive attitude from the public towards the introduction of hydrogen as an energy source, but there is still some negative perception due to the risk of an accident with this type of fuel.

It is true that hydrogen accidents have happened and its introduction hydrogen as an important energy carrier should be handled in a safe manner.

Example of incidents occurring in the 2000s:

2009, an explosion occurred at a power plant near Beverly, Ohio, killed one person and injured 10 others. The incident occurred when delivering compressed hydrogen to storage tanks on site. A pressure relief valve failed, followed by damage to the connected vent line resulting in hydrogen build-up under a roof structure. The hydrogen cloud was ignited and the ensuing explosion. Several buildings near the delivery location were severely damaged.

2019 a hydrogen tank explosion occurred in Gangneung, South Korea killing two people and damaging several buildings. The explosion occurred at a P2G plant using water electrolysis. Oxygen managed to permeate into a 40 m3, 10 bar hydrogen storage tank. The most likely ignition source could not be established.

2019, an explosion and fire occurred at the hydrogen fueling station in Kjørbo near Oslo, Norway. The root cause of the incident was an assembly error in the high-pressure storage unit at the station resulting in a small leak that escalated into a much larger leak, creating a hydrogen-air mixture that got ignited and resulted in a strong explosion and an ensuing fire. The consequences of the explosion and fire were limited to damages to the hydrogen fueling station but was however heard kilometers away.

The accidents that have happened are mainly related to the combustibility and ignitability of hydrogen: Hydrogen is very reactive and prone to a deflagration-to-detonation transition and has a very low minimum ignition energy. On the other hand, hydrogen has also some properties making it safer than other fuels: hydrogen is not toxic and has a very low density causing it to move upwards immediately after release. Assessing the hazards of hydrogen is therefore not straightforward and depends on many aspects: geometry in which the hydrogen is applied, the storage conditions (high pressure, liquified, inventory), ventilation conditions, presence of ignition sources, what can be exposed, etc.

While hydrogen has been used for decades and is currently regulated under various regulations (such as the ATEX-Directives, the Seveso-Directive and country-specific regulations; see e.g. https://www.hylaw.eu/ for Europe) and supporting standards (NFPA2, ISO/TR 15916, NFPA 55, ISO 19880-1 and ISO 22734) there is a need for adapting regulations to the upcoming hydrogen economy and standards supporting these regulations. Examples are the Alternative Fuels Infrastructure Directive (AFID), the European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR) and legislation related to the injection of hydrogen into natural gas networks. Standards supporting implementation of these regulations are developed in e.g. the ISO TC 197 “Hydrogen Technologies”, the IEC TC 105 ”Fuel Cell Technologies” and the CEN-CLC JTC 6 “Hydrogen in energy systems”. Safety plays an important role in these standards.

Research has been and still is ongoing addressing several safety aspects of using hydrogen. For gaseous hydrogen (GH2) this includes gas cloud build-up in ventilated rooms, a study on the properties of GH2 jet fires, spontaneous ignition and flame propagation in congested environments including deflagration-to-detonation transition. For liquified hydrogen (LH2) investigated topics include BLEVEs of storage vessels, releases of LH2 on and under water, combustion and dispersion of clouds developing from LH2 pools, ignition by electrostatic charging during releases of LH2 and effect of temperature on combustion properties of H2 and LH2 jet fires. The research concerns both experimental and modelling efforts and in the still ongoing research aspects such as tunnel safety, explosion mitigation and jet fires of LH2 are addressed.

At Vysus Group, we have a unique set of competences built up through our involvement in many research projects, hazard and safety assessment of hydrogen systems and management of hydrogen assets to help you to predict, mitigate and prevent such events in an optimised way. From hazard identification, process safety, consequence modelling, emergency preparedness to organisational measures.

Considering hydrogen safety, we offer consequence modelling using both Computational Fluid Dynamics based industry standard tools combined with inhouse developed screening tools. The results of these calculations in conjunction with results using models predicting leak frequencies and ignition frequencies allow for estimating risks and comparing those to acceptance criteria. We also offer other services such as HAZID (Hazard Identification) studies of hydrogen systems to identify potential hazards and threats to people and equipment and HAZOPs to also address risks to people and equipment. Determination of the Safety Integrity Level of hydrogen systems to determine the requirements for instrumented risk reduction measures is also offered.

In future articles/blogs we will address several safety related aspects related to the introduction of a hydrogen economy in far more detail. We will also describe the various safety assessment methods used for hydrogen systems with examples showing their benefits to bring residual risks to an acceptable level.

The establishment of a hydrogen economy to replace a large part of the fossil fuels is an important element to established a decarbonised energy sector.

Kees Van Wingerden

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