‘The successful scale-up of hydrogen hinges on process safety’

If we want to scale up green hydrogen production to a level of significance for the energy transition, attention to safety is a ‘must’. ISPT previously conducted a study that identified the fundamental safety aspects of green hydrogen production. A second study looked at industrial-scale hydrogen production using two different processes. This resulted in generic hazard scenarios of hydrogen electrolysers that can be used by OEMs and operators for their process risk assessments. It also includes an overview of the Dutch directive NPR7910-1 and its applicability for ATEX zoning purposes.

Hydrogen plays an important role in the energy transtion. By replacing hydrogen produced with fossil fuels with (green) hydrogen from renewable energy sources, we can reduce our dependence on oil, gas, and coal and reduce our CO₂ emissions. A mature hydrogen economy in Europe can alsso contribute to employment, economic growth and energy independency from other regions.

However, significantly scaling up production is essential – and far from straightforward. In addition to challenges regarding the availability and affordability of sufficient renewable energy, it is crucial to conduct research into the safety of these large-scale processes. Hydrogen, for example, has a low ignition energy, which presents a potential explosion risk to both the plant and its surroundings.

A first step

The importance of safety was also demonstrated in the innovative design for a green hydrogen plant presented by ISPT in 2022. This plant has a capacity of 1 GW and is capable of producing hydrogen through both Alkaline Water Electrolysis (AWE) and Proton Exchange Membrane (PEM) electrolysis. Safety aspects were explored as part of the project ‘Green Hydrogen Inherent Safety Practices on Large Industrial Scale‘.

This project revealed, among other things, that there is insufficient knowledge among suppliers, engineering contractors and end users when it comes to the safety of large-scale hydrogen production. Moreover, the research showed that existing laws and regulations are not specefic enough for green hydrogen production, which highlights the urgent need for standardisation in electrolysis safety.

Conclusions report Safety standardisation

The knowledge gaps concerning safety aspects were further explored in the project ‘H2-Safety2 – Safety Standardisation of Green Hydrogen Electrolyser Systems‘. This project is the result of over two years of research, in close collaboration with safety experts from Battolyser Systems, Equinor, Green Hydrogen Systems, HyCC, ISPT, John Cockerill, NEN, Ørsted, Plug Power, RHDHV, RWE, Shell, TNO, VoltH2 and Yara.

Generic hazard scenarios

The generic hazard scenarios identified in the study concern fire and explosion risks associated with both AWE and PEM technologies. These scenarios may relate to design aspects, the production and maintenance of membranes, degradation of cell and stack components, and failures in process control systems.

One of the key conclusions is that the risks associated with water electrolysis systems can be reduced to an acceptable level – provided that risk assessment and mitigation methods commonly applied in (petro)chemical installations are also implemented here. Van ’t Noordende explains: “An effective Process Safety Management (PSM) system is essential. This includes not only organisational procedures such as Management of Change (MOC), but also HAZOP and LOPA assessments, inherently safe design, and (instrumented) safety measures such as Safety Integrity Levels (SIL). To define the required safety measures, installation-specific details are crucial – once again underlining the importance of close collaboration with electrolyser manufacturers.”

An effective standard for safety starts with shared knowledge

The risk analysis also highlights several technical safety measures. The primary one is the detection of excessive hydrogen and oxygen concentrations within the equipment. The studies indicate that in certain scenarios, electrolysis processes can proceed so rapidly that gas detectors are too slow to respond effectively — especially when not positioned close enough to the source of the concentration. Furthermore, sensors capable of measuring within a two-phase (gas/liquid) flow are not yet available, making reliable detection in such fast-evolving situations a continued challenge. Another important finding was that hydrogen (and oxygen) can also accumulate in auxiliary equipment, such as cooling circuits, due to internal leakages.

Additionally, the use of renewable energy introduces a unique operational context: the load on the production system fluctuates with the availability of solar and wind power. This results in frequent switching between low and normal loads. Richard Bollen explains: “This is not expected to directly impact the safety of electrolysis systems. However, frequent start-up and shut-down of components will likely contribute to membrane degradation. The challenge is that this degradation cannot be monitored directly — it must be inferred from other process parameters, such as (gradual) changes in plant output or efficiency, cell and stack voltages, and gas concentrations.”

Legislation and Regulation

The applicable legislation for hydrogen safety primarily focuses on the ATEX directive for explosive atmospheres. These regulations are essential for assessing the likelihood of gas explosions and fires, as well as for spatial zoning in urban planning. In the Netherlands, zoning is typically based on NPR7910-1. However, this guideline was developed mainly for organic vapours — which are much heavier than hydrogen — and is therefore not suitable for hydrogen applications. Instead, the European standard IEC60079-10-1 is used for zoning hydrogen production facilities.

Other ATEX-related aspects, such as ventilation and the prevention of flammable substance accumulation, are also relevant to hydrogen. Ventilation — whether forced or natural — is only effective in controlling leaks that fall within the ATEX scope. It is, however, insufficient to prevent the formation of a flammable cloud in case of major leaks or accidents. Van ’t Noordende notes: “Standardisation of electrolysers will continue at the international level through the revision of ISO 22734 and other frameworks, such as DNV JT301, and at the national level through NTA 8221 (Process safety for hydrogen production via electrolysis) and PGS 40 – Hydrogen Production. Continued alignment between industry and authorities is essential, as is the sharing of best practices.”

Time to move forward

The H2-Safety2 project has built up valuable knowledge and activated regulatory bodies. The next step is to gain hands-on experience and share best practices. To achieve this, the construction of pilot plants is essential. Bollen explains: “This practical experience is particularly important because we anticipate an increasing move towards modular construction — driven by the availability of renewable energy sources and the possible integration of different electrolysis technologies. Every new module configuration raises the same fundamental questions: where can things go wrong, what are the risks, how can we eliminate them, and what measures are needed to minimise any residual risks?”

Van ’t Noordende and Bollen conclude: “This is an open innovation centre that will, in the future, also offer space for suppliers to test and optimise their innovative products, such as electrolyser components, at industrial scale. The ultimate goal is to use innovation to improve the robustness, flexibility and efficiency of large-scale green hydrogen production, lower the costs, and accelerate the energy transition.”

This article was previously published in NPT Procestechnologie magazine and online on npt.pmg.nl