NOWIcob - A tool for reducing the maintenance costs of offshore wind farms

It is essential to implement cost-effective operation and maintenance concepts and strategies to achieve a significant reduction of cost of energy from offshore wind farms. A decision support tool (Norwegian offshore wind cost and benefit model - NOWIcob) was developed that simulates the operational phase of an offshore wind farm with all maintenance activities and costs. This tool can be used to understand sensitivities of the operation and maintenance costs due to changes in the maintenance and logistic strategy, and helps to choose an optimized strategy for a specific wind farm. The model is based on a time-sequential event-based Monte Carlo technique and takes into consideration weather uncertainty and other relevant aspects for the operational phase of an offshore wind farm. Different vessel concepts for accessing the wind farm and time-based, condition-based and corrective maintenance tasks can be simulated. The model delivers results in form of availability, life cycle profit, operation and maintenance cost, produced electricity and other performance criteria. The main characteristics and the underlying scientific models will be described. In addition, application of the NOWIcob model will be demonstrated for a theoretical case of a far-offshore wind farm using a mothership / daughter ship vessel concept, and benefits of using such a tool will be highlighted. (C) 2013 The Authors. Published by Elsevier Ltd.