Safety and Reliability Analysis of an Ammonia-Powered Fuel-Cell System

Abstract

Recently, the shipping industry has been under increasing pressure to improve its environmental impact with a target of a 50% reduction in greenhouse gas emissions by 2050, compared to the 2008 levels. For this reason, great attention has been placed on alternative zero-carbon fuels, specifically ammonia, which is considered a promising solution for shipping decarbonisation. In this respect, a novel ammonia-powered fuel-cell configuration is proposed as an energy-efficient power generation configuration with excellent environmental performance. However, there are safety and reliability concerns of the proposed ammonia-powered system that need to be addressed prior to its wider acceptance by the maritime community. Therefore, this is the first attempt to holistically examine the safety, operability, and reliability of an ammonia fuel-cell-powered ship, while considering the bunkering and fuel specifications. The proposed methodology includes the novel combination of a systematic preliminary hazard identification process with a functional and model-based approach for simulating the impact of various hazards. Furthermore, the critical faults and functional failures of the proposed system are identified and ranked according to their importance. This work can be beneficial for both shipowners and policymakers by introducing technical innovation and for supporting the future regulatory framework.

Towards Trustworthy Safety Assessment by Providing Expert and Tool-Based XMECA Techniques

“…• elements fi (for instance, module components, program operators, process operations, etc. ), failures of which are to be considered, that is fi ϵ ΔF, ΔF ϲ MF, where ΔF is a subset of components investigated; MF is a set of components; • failure modes mij of element fi, which are to be considered, i.e., mij ϵ ΔMi, ΔMi ϲ MMi (7) where ΔMi is a set of elements fi failures investigated; MMi is a set of all element fi failures;…”

“…MM i (7) where ∆M i is a set of elements f i failures investigated; MM i is a set of all element f i failures;…”

“…MEi, ∆Ei(q) is a set of failure effects of element f i considered by a q-th expert definition of different probabilities of failure modes m ij of element f i set M∆Pij of sets ∆Pij(q), for all q, ∆Pij(q) 7 of 25 k = k1 + k2 + … + kF (6) e interrelation between previously mentioned fi, mi, and ei, and the nd ci is shown in Figure 3. aracterized by number of rows F* = F, if k1 = k2 = … = kF = 1; in a MECA execution, the following items are sequentially defined by tool support: stance, module components, program operators, process operaof which are to be considered, that is fi ϵ ΔF, ΔF ϲ MF, where ΔF is ents investigated; MF is a set of components; f element fi, which are to be considered, i.e., mij ϵ ΔMi, ΔMi ϲ MMi (7) ments fi failures investigated; MMi is a set of all element fi failures; mode mij of element fi, which are to be considered, i.e., eij ϵ ΔEi, ΔEi ϲ MEi (8) ilure effects defined by an expert for a particular failure mode mij s a set of all possible effects for a particular failure mode of this severity sij of failure mode mij of element fi; probability pij and seadopted according to defined scale on the sets of values MP = {p'h} rdingly; criticality сij of failure mode mij of element fi, which could evaluated by an expert using given function φ or assigned by an n the set of values MС = {с'g}.…”

“…CA table is characterized by number of rows F* = F, if k1 = k2 = … = kF = 1; in a ay, F* = K. e process of FMECA execution, the following items are sequentially defined by with possible tool support: ents fi (for instance, module components, program operators, process opera-, etc. ), failures of which are to be considered, that is fi ϵ ΔF, ΔF ϲ MF, where ΔF is set of components investigated; MF is a set of components; re modes mij of element fi, which are to be considered, i.e., mij ϵ ΔMi, ΔMi ϲ MMi (7) i is a set of elements fi failures investigated; MMi is a set of all element fi failures; ts eij of failure mode mij of element fi, which are to be considered, i.e., eij ϵ ΔEi, ΔEi ϲ MEi (8) i is a set of failure effects defined by an expert for a particular failure mode mij ent fii; MEi is a set of all possible effects for a particular failure mode of this ability pij and severity sij of failure mode mij of element fi; probability pij and sey sij are being adopted according to defined scale on the sets of values MP = {p'h} MS = {s'g} accordingly; criticality сij of failure mode mij of element fi, which could ither explicitly evaluated by an expert using given function φ or assigned by an MS ∆Si(q) is a set of failure severities of element f i considered by a q-th expert obtained different criticalities of failure modes m ij of element f i set M∆Ci of sets ∆Ci(q), for all q, ∆Ci(q)…”

“…Another challenge is related to the existence of a variety of safety assessment approaches and their modifications (including techniques for safety constituents, such as functional safety, cybersecurity, etc.). There are many assessment techniques (FMECAfailure modes, effects, and criticality analysis, FTA-fault tree analysis, HAZOP-hazard and operability study, HAZID-hazard identification study [5][6][7]) that can be applied separately and jointly to guarantee the trustworthiness of results. Besides, there is a problem of incompatibility and inconsistency of their outputs in the general case [8], etc.…”