FACTORS INFLUENCING THE MAINTENANCE OF OFFSHORE WIND TURBINE FOUNDATIONS: A SURVEY BASED ON EXPERT OPINION

Abstract: The wind industry is growing rapidly and especially in Europe, offshore wind power has become a serious business with approximately 22 GW installed in 2019. However, for the industry to become even more competitive, costs must be reduced. Especially the Operation and Maintenance (O&M) costs present a challenge to developers and operators. In order to achieve cost savings during the operational phase, the factors influencing the maintenance operations should be identified. This Thesis focuses on the factors influencing the offshore wind turbine foundation maintenance operations. The aim of the Thesis is to identify these factors and their attributes, as well as rank them according to their importance. First, a literature review was conducted to establish the theoretical background for this study. In order to do so, maintenance strategies, offshore wind turbine foundations and the scope of foundation maintenance were described in detail. After that, the factors influencing the maintenance for offshore wind turbine foundations were collected from literature, personal experience, and input from industry experts. Following that, a two-step study with seven industry experts was conducted to validate these factors and their attributes as a first step before then ranking all the attributes by their importance. The experts were asked to rank each attribute by assigning a number from 1-5 where: very high influence (5), high influence (4), medium influence (3), low influence (2) and no influence (1). Since the maintenance differs for the subsea and the above water part of the foundation, the participants had to rank each attribute twice, once for the subsea part and once for the part above water. After the results were analyzed, it can be concluded that the Quality Health Safety Environment (QHSE) was ranked as the most important, followed by technology and standards & guidelines. The environment factor was ranked as the least important before the geographical location and cost factors.