Hydrogen - environmental benefits but at the cost of safety?
There is much discussion within society about the use of Hydrogen as a fuel of the future to meet decarbonisation targets. Significant proportions of this discussion relate to green versus blue Hydrogen and how industry can develop a truly sustainable form of energy. While these discussions are dominated by the environmental aspects of producing, storing, and using Hydrogen it is important not to lose sight of the impact upon safety.
To some, Hydrogen creates the perception of danger and large explosions, no doubt through historical events such as the Hindenburg disaster. Is Hydrogen particularly unsafe and, following on from this question, is it appropriate as a fuel used by the general population? The answer of course is that “it depends”.
By way of analogy, we can look back to the discussions on the environmental benefits of Hydrogen, because these are, also, largely dependent upon the detail. For instance, if Hydrogen has been manufactured by reforming methane and then compressed using grid electricity made from burning coal then no environmental benefit is derived. Should renewable electricity be used to generate Hydrogen from water and then further used in compression, then there are potential environmental benefits. Similarly, the risk with respect to Hydrogen is dependent upon the context of how it is made and used along with the form it is stored in. Furthermore, risk itself is best understood not by looking at Hydrogen in isolation but establishing how it compares to competing technologies such as Natural Gas or Petroleum.
From a technical perspective, Hydrogen is neither substantially more nor less “dangerous” than many other competing fuels. It is just different, and it is these differences which need to be understood so that effective safeguards can be implemented. Those who have worked with Hydrogen in industry can point to the extremely low ignition energy required to ignite it in comparison with other fuels. This, however, has minimal impact on the risk when you recognise that most of the typical ignition sources can ignite Petroleum or Natural Gas anyway. Hydrogen could also be considered “more risky” due to its wide flammable range, typically high storage pressures and containment issues due to Hydrogen’s ability to easily find leak paths.
Although this is true, Hydrogen also has great buoyancy and can ventilate away easily if the location of use is designed correctly. Competing fuels, such as Natural Gas or Petroleum, would generate flammable clouds which could persist for longer periods while Petroleum would create low level vapours. The wider flammable range of Hydrogen also does not necessarily mean that the risk is greater. Hazard ranges from a flammability perspective are driven by the lower explosive limit (LEL) rather than the flammable range. In this respect, Hydrogen is similar to competing fuels such as Natural Gas, while Petroleum actually has a lower LEL. Again, this is not about better or worse, just a different problem which requires a different solution.
From a risk perspective, the likely dominating factor in the move towards Hydrogen fuels in non-industrial settings is the people using it. This can be understood on two levels: perceived risk, and actual risk. The public are likely to perceive the risk of Hydrogen as larger than it is, given the unfamiliarity in comparison with known, existing technologies. Additionally, where some public knowledge regarding Hydrogen is acquired, it is likely to have emanated from a negative incident. This high perceived risk is, however, a good thing. Currently, incidents within the Hydrogen industry are infrequent, no doubt due to accumulated experience and competence of the industry and its people. Familiarity can, however, breed contempt and there are trade-offs between experience and complacency. The challenge when using Hydrogen as a future fuel for the public is to transfer the knowledge and competence to the users, during which a higher perceived risk by the public is undoubtedly a good thing.
As society moves towards a more extensive use of Hydrogen as a fuel, there are many considerations to make to ensure that risks are reduced to appropriate levels. From a safety perspective we should ask ourselves:
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