D1C.5 Risks involved in the use of hydrogen instead of natural gas
A study was recently carried out within the framework of the national HyDelta research programme into the risks related to existing gas installations at domestic gas consumers after the conversion from natural gas to 100% hydrogen. The study is aimed at gaining more insight into whether additional measures should be taken to ensure the existing safety level of an indoor installation is maintained. Determining the effect of these measures on the risk is not part of this study.
Records of natural gas-related accidents during the period from 2010 to 2020 were also analysed. These records concerns (flash) fires, explosions and carbon monoxide poisoning. When switching to hydrogen, the risk of carbon monoxide poisoning is eliminated. The risk of fire or explosion, on the other hand, may increase. Information from leak-tightness tests in the field was also analysed - three sources in total - of which the largest source came from 1.4 million gas connections. The analysis shows that 1 to 2% of existing pipe installations are leaking (0.1 - 1 dm3/h), without this causing problems and without this being noticed by the residents. Pilot projects involving households with a hydrogen installation show that additional technical and organisational safety measures have been or are being taken due to the experimental nature of the projects. In the current pilot projects in the Netherlands, cooking hobs that use hydrogen are excluded.
Using a risk assessment based on the Fine and Kinney model, different scenarios were mapped out in which an incident would lead to injury or death. Each scenario was given a risk index, both for natural gas and hydrogen.
The main conclusions relating to the additional risks involved with switching from natural gas to hydrogen are as follows:
- The probability of carbon monoxide poisoning is reduced from 19.6 affected persons per million gas connections per year (of which 0.37 are fatal; the Dutch “Onderzoeksraad voor Veiligheid” is estimating these amounts higher) to 0 incidents per year.
- The risk of injury from minor gas leaks remains extremely small.
- The risk of injury in the event of large gas leaks, other than CO poisoning, will increase. At present, the number of injuries is 1.16 per one million connections per year (of which 0.06 are fatal).
Some additional mitigating measures that can prevent major gas leaks and/or adverse consequences are installing an excess flow valve (excess flow valve or flow restrictor; automatic shut of valve which is closing when exceeding a set gas flow) and inspecting the gas pipe installation (visually, for strength and tightness) before switching to hydrogen.
|Context of this report
For the use of hydrogen distribution in the energy transition, a safety level is assumed that should be at least equivalent to that of the existing natural gas distribution. This report gives a picture of which risks are greater or smaller with hydrogen, if the set of mitigating measures for natural gas is maintained. For the situations where a risk is greater, the set of mitigating measures for hydrogen will be adapted in order to maintain the level of safety. This report only provides a qualitative comparison of the risks for hydrogen in relation to natural gas, based on the set of mitigating measures such as natural gas: is it higher, lower or equal. In HyDelta work package 1A quantitative research is done into the extent to which risks change and which adapted mitigating measures are effective in those situations.
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