PNR for a safe use of liquid hydrogen
As a prenormative project the topic addresses mainly those areas where LH2 specific standards do not exist or should get reworked. Rather it addresses all safety related standards and regulations (ATEX directive, etc…) requiring a minimum safety performance of the respective technology (refuelling, transport, etc). However, there are a few international standards already dealing with LH2 like ISO 13984:1999 Liquid hydrogen – Land vehicle fuelling system interface, ISO 13985:2006 Liquid hydrogen – Land vehicle fuel tanks, the ISO/TR 15916:2015 Basic considerations for the safety of hydrogen systems, or ISO Standard 21012:2006 Cryogenic vessels – Hoses (Applicable to fuel storage system design) which should be revised on the basis of the outcome of the project. As EU regulations are built on or tend to refer to international standards (“modern approach”) there are actually no LH2 specific regulations at all.
For scaling up the hydrogen supply infrastructure the transport of liquefied hydrogen is the most effective option due to the energy density. Especially for the transport sector with the planned large bus fleets, the emerging hydrogen fuelled train, boat and truck projects and even for the pre-cooled 70 MPa car refuelling liquid hydrogen (LH2) offers sufficient densities and gains in efficiency over gaseous transport, storage and supply. However, LH2 implies specific hazards and risks, which are very different from those associated with the relatively well-known compressed gaseous hydrogen. Although these specific issues are usually well reflected and managed in large-scale industry and aerospace applications of LH2, experience with LH2 in a distributed energy system is lacking. Transport and storage of LH2 in urban areas and the daily use by the untrained general public will require higher levels of safety provisions accounting for the very special properties. The quite different operational conditions compared with the industrial environment and therefore also different potential accident scenarios will put an emphasis on specific related phenomena which are still not well understood. Specific recommendations and harmonised performance based international standards are lacking for similar reasons. However, for a safe scale-up of the described promising hydrogen solutions science based and validated tools for hydrogen safety engineering and risk informed, performance based, international standards specific for LH2 technologies are imperative.
So the potential for increased handling and distribution of LH2 in the public highlights the need to address unanswered questions related to these prototypical accident scenarios via pre-normative research, thorough laboratory scale experimental and theoretical investigations. In particular, appropriate models for the flashing multiphase, multicomponent release phenomena, cryogenic plumes and jets, the potential for flame acceleration and deflagration-detonation-transition in these multiphase mixtures, have to be developed on a new experimental basis. The suitability of conventional mitigation techniques needs to be checked carefully and partially overly conservative safety distance requirements have to be revised on the basis of an improved understanding of the physics and with the help of the new models. The intrinsic safety advantages of LH2 over compressed hydrogen offer indeed a high potential for safer, more economic innovative solutions. However, this potential might be used only if the required knowledge base is provided.
The scope of this topic encompasses pre-normative research on the associated risks related to the accidental behaviour of LH2 and finally the derivation of suitable engineering correlations and enhanced recommendations for safe design and operations of LH2 technologies.
In a more detailed view, the envisaged project shall develop a suitable detailed experimental program, which shall be derived from internationally agreed priorities. The preliminary list of critical phenomena presented in the specific challenge paragraph above has to be revised to comply with those topics which receive highest ranks from all stakeholders, mainly research and industry. Thus the generated experimental program and the accompanying analytical and numerical studies will improve the understanding of the most relevant safety related issues of distributed use of LH2 in the most efficient way.
The generated experimental results shall be extensively documented, published and translated into easily applied, but sufficiently conservative criteria or engineering correlations, directly applicable in the design process or associated risk assessment procedures. Implementation of the criteria and correlations in an open software integration platform for risk assessment or improved design of mitigation concepts shall be envisaged. New recommendations and guidelines including appropriate safety distance correlations and advice for proper use of mitigation technologies shall be derived. Thus, the results shall support the further development of the related specific international standards via a solid extended scientific basis. A set of communication peer reviewed papers shall be prepared, suitable to internationally disseminate the findings of the project to the different stakeholders.
Termin nadsyłania zgłoszeń
20 kwiecień 2017