Availability-Based Selection of Electricity Delivery Network in Marine Conversion Systems Using Bayesian Network

Availability is an economically important metric used to assess the design of marine energy farms. Nowadays, three typical concepts of energy delivery network topologies have been proposed for marine energy conversion systems. Few research works assessing the availability of marine energy conversion systems have been published. Their methodology is only based upon time-consuming Monte Carlo simulations and only covers one maintenance strategy. The objective of this study is to consider different maintenance strategies and quantitatively assess the time-dependent availability of these typical energy delivery network topologies by investigating the working philosophy of these topologies and modelling the logic dependencies of them in a Bayesian network (BN). The working philosophy of each topology is investigated to obtain the logic dependencies of the units in the energy delivery network, by means of qualitative system analysis. A table-like data structure, called hierarchy, is introduced to store the information on the logic dependencies and serves as a basis for establishing the corresponding BN models. A logic gate in the hierarchy can be represented by a conditional probability table in the BN model. The availability of these topologies, as a function of time, can be estimated through the BN models. The optimal topology can be selected, based upon the time-dependent availability

Risk‐based derivation of target reliability levels for life extension of wind turbine structural components

Abstract The main wind turbine design standard IEC61400‐1 ed. 4 includes an annual target reliability index for structural components of 3.3. Presently, no standards specify specific reliability requirements for existing wind turbines, to be used in relation to verification of structural integrity for life extension or continued operation. For existing structures in general, both economic and sustainability considerations support differentiation in reliability targets, as it is generally more expensive and requires more resources to improve the reliability. ISO2394 “General Principles on Reliability for Structures” includes tables with differentiated reliability targets depending on the consequences of failure and costs of improving reliability, which are derived using risk‐based economic optimization. However, the assumptions behind these tables do not match the specific problem of life extension of wind turbines. In this paper, the risk‐based approach is applied to derive specific target reliability levels for life extension of wind turbines, and a target annual reliability index around 3.1 is proposed