Wind Power Performance Optimization Considering Redundancy and Opportunistic Maintenance

In This paper the redundancy and imperfect opportunistic maintenance optimization of a multi-state weighted k-out-of-n system is formulated. The objective is to determine the k-out-of-n system redundancy level and the maintenance strategy which will minimize the wind farm life cycle cost subject to an availability constraint. A new condition based opportunistic maintenance approach is developed. Different component health state thresholds are introduced for imperfect maintenance of failed subsystems and working subsystems and preventive dispatching of maintenance teams. In addition, a simulation method is developed to evaluate the performance measures of the system considering different types of subsystems, maintenance activation delays and durations, limited number of maintenance teams, and discrete inspection of the system. Also, a multi-seed tabu search heuristic algorithm is also proposed to solve the formulated problem. An application to the optimal design of a wind farm is provided to illustrate the proposed approach

Algorithmic Strategy for Simultaneous Optimization of Design and Maintenance of Multi-Component Industrial Systems

This article describes a new approach to simultaneous optimization of design and maintenance of large-scale multi-component industrial systems. This approach, in a form of an algorithm, aims to help designers in the search for solutions by characterizing the components and their architecture including maintenance issues. The aim is to improve the performance of the industrial systems by maximizing the Total Operational Reliability (TOR) at the lowest Life Cycle Cost (LCC). In the case of this research, the term "design" refers to the reliability properties of the components, possible redundancies, faulty component accessibility, and the ability to improve the component real-time monitoring architecture. The term “maintenance” refers to maintenance plan adapted to the opportunistic dynamic maintenance plan. Simultaneous optimization of design and maintenance is achieved by a two-level hybrid algorithm using evolutionary (genetic) algorithms. The first level identifies the optimal design solutions calculated relative to the TOR and the LCC. The second proposes a dynamic maintenance plan that maximizes the reliability of the system throughout its operating life

Framework for Evaluation of Strategies for Pooling of Repairable Spare Parts

Background: The ability to quickly provide parts for the supply of advanced technical systems in equipment-intensive industries (such as airlines and nuclear power plants) is critical to the systems overall performance. In order to maintain a targeted system availability large quantities of spare parts are often required which in turn results in excessive inventory costs. Seeing as inventory systems often account for a large proportion of a business‟ costs a tough issue faced by companies in these industries is how to reduce the total inventory cost without having a negative impact on the system availability. An approach that may successfully deal with such a problem is pooling. Pooling refers to an arrangement in which multiple owners of the same type of technical systems cooperate by sharing their inventories. Purpose: The theoretical purpose of the thesis is to emphasize different pooling strategies and to identify and assess the characteristics of the strategies. The practical purpose of the thesis is to develop a robust method that facilitates a fair comparison of considered strategies. The objective is thus to develop a generic model that evaluates soft values (here, referred to as soft aspects) for each strategy, and also, to put the soft aspects in relation to the annual cost of a strategy in a final model. iv Methodology: The initial phase of the thesis was dedicated to a desk study review of current literature within the field of study. Recently published scientific articles, papers authored by consultants at Systecon, and literature used in courses at the Faculty of Engineering at Lund University lay the basis for the theoretical framework. The framework developed is derived from discussions with the supervisors in connection with interviews carried out with; relevant Systecon customers and company representatives at two trade fairs, Offshore Wind 2009 and Nordic Rail 2009. Conclusion: This thesis presents a framework for evaluation of strategies (stand alone, ad hoc cooperation, cooperative pooling, and commercial pooling) for pooling of repairable spare parts. Characteristics of all strategies are emphasized and assessed. From the characteristics, which are provided in Table 5.3, a model to evaluate soft values of each strategy is derived. The model, named evaluation of soft values, is provided in Table 5.4 and Table 5.5. Also, a methodical approach to derive a final strategy is provided in section 5.7. To make sure that a decision-maker is well aware of how the model should be applied, a fictitious case study is build up in where every step of the decision making process is thoroughly described. Furthermore, in the case study a final model that facilitates the derivation of a best strategy is presented. By means of a specified weighting coefficient and properly chosen set of scales, the final model provides with a final strategy. The outcome of the final model is based on the outcomes of the cost models and the outcomes of the evaluation of soft values model