Operation and maintenance (O&M) costs constitute the biggest share (more than 30%) of lifecycle cost for offshore wind energy, indicating enormous costs are expected to be invested in O&M in the near future along with the increasing operational capacity all over the world. The limited number of papers studying maintenance inventory commonly only notice component-level spare parts, and adopt a single-echelon inventory warehouse. These studies are not adequate enough for offshore wind turbines, because offshore wind turbines is a typical complex system not only consisting of different component-level units, but also various subcomponent-level units. These units are usually stored in warehouses at different echelons considering differences in size, weight, and maintenance requirements, instead of a single warehouse. Therefore, in this paper, we proposed a multi-echelon inventory optimization model. In this model, the wind turbine construction is decomposed into three hierarchical levels, i.e., turbine-level, component-level, and subcomponent-level. A warehouse network is developed following a multi-echelon structure. The proposed model was applied in a case study of an offshore wind farm located in the North Sea to assess its performance. A meta-heuristic algorithm is employed to find the optimal inventory policies in order to minimize the total inventory management costs.


The offshore wind energy sector has been experiencing remarkable growth in the Netherlands. With the significant increase in the annual new installation, maintaining the operation of the wind farms has become more vital and challenging. For offshore wind farms, Operation and Maintenance (O&M) costs constitute about 30% of the lifecycle cost (Li, Jiang, Carroll, and Negenborn, 2022). Among all the cost categories of O&M, regular maintenance, repair and spare parts account for the highest portion, about 43% (El-Thalji, Alsyouf, and Göran, 2009).

A well-organized spare parts inventory policy is deemed essential to improve the O&M of the offshore wind energy and enhance its competitiveness within the renewable energy market. Spare parts inventory management and maintenance management are interrelated (Van Horenbeek, Buré, Cattrysse, Pintelon, and Vansteenwegen, 2013). The stock level of spare parts is determined by the demand caused by the maintenance implementation. Meanwhile, maintenance implementation depends on the availability of spare parts to reduce failure downtime and costs.

This content is only available via PDF.
You can access this article if you purchase or spend a download.