Abstract
Offshore wind energy is a renewable source with strong prospects of development that may decisively contribute to guarantee energy independence for several world countries. Worldwide offshore wind capacity has increased significantly over the past decade with 22 GW installed by the end of 2018; this capacity presents itself as an effective tool for several countries to address their renewable production targets, as extensive areas of strong winds are available offshore. However, offshore wind is not yet cost competitive within the European electricity markets, and frequently requires support schemes to finance the extensive capital cost requirements. Therefore, cost reductions are critical to make offshore wind technologies competitive within the electricity markets.
Structural Health Monitoring systems are currently used in the inspection of the structural integrity of mechanical structures, with the main goal of guaranteeing safe operation, thus minimizing failure occurrence – they can, then, contribute to cost reduction within offshore wind implementation. Until now, structural health monitoring systems have not been the focus of much research from the agencies and stakeholders regarding its implementation in the OSW field. Towers and foundations can indeed be considered to be very reliable structures. This does not mean, however, that these structures are flawless, which means monitoring systems may possess a relevant role on OSW operations in the future.
The main objective of this work is to evaluate the viability of structural health monitoring systems on the support structures of offshore wind. This evaluation is sustained by a holistic framework which is divided in three different branches of research.
Firstly, the evaluation of the socio-economic and environmental impacts of offshore wind implementation is done. It is fundamental to understand what are the policy frameworks that are necessary to promote the installation of technologies that are not yet commercially competitive, and how these frameworks are shaping themselves to help bring costs down.
Then, the technical implementation of structural health monitoring systems on offshore wind supporting structures is investigated. A computationally aided engineering methodology is used to provide insights on the types of monitoring systems which are most relevant, and the cost of these systems is estimated at the end using data provided by sensor manufacturers and providers.
Finally, the impact of structural health monitoring systems on the life-cycle costs of offshore wind is evaluated, using several economic models that estimate the capital expenditures of future farms, the impact of using structural monitoring systems on the revenues of the farm, and the overall non-discounted and discounted cash flows of a certain farm. A model that evaluates the optimum year for farm repowering, considering that turbines are getting more efficient, powerful and cheaper, is also presented.
The general results obtained from the produced research seem to indicate that installing structural health monitoring systems on the support structures of offshore wind can provide economic benefits related with potential savings from insurance costs. Moreover, the use of these systems can shift the maintenance strategies from preventive to predictive-based, which allows the intervals between inspections to be increased without equipment loss. However, the greatest benefit seems to be related with the possibility of extending the operational life of a certain farm, as this may result in additional revenues of dozens or hundreds of millions of euros.
Also, the research concluded that monitoring the support structures of a certain farm at a particular cadency (for example, one in each 10 foundations), as it is currently defined on the respective standards, does not seem to provide any of the benefits that these systems can bring at the operational and economic levels.