Offshore wind plays a major role in the transition of conventional energy towards sustainable energy sources. To keep up with the increasing installation demand in this sector new offshore wind installation vessels are needed. There is a need for more certainty and predictability regarding the requirements of the future offshore wind installation vessels. To translate the market developments towards input variables for future vessel concept designs, the methods ’needs analysis’ and ’concept exploration’ from the systems engineering framework are applied. Epoch-era analysis is selected as scenario modelling method to capture the uncertain and the fast changing market by generating various future possibilities each posing different vessel requirements. A parametric model is created to determine the performance of a set of vessels defined by their length, beam, depth, crane capacity, speed, and transport strategy. The case study shows that the application of Epoch-era analysis and parametric modelling is capable of generating insights in important aspects for designing future offshore wind installation vessels. The strength of this method is that it has the flexibility to select different key performance indicators but also provides the opportunity to incorporate the importance of short term against long term goals. It can therefore be tailor-made to a stakeholders strategy. Applying their wishes while analysing many different options results in robust input variables for the concept vessel design.

Offshore wind energy can play a key role in the energy transition. Reducing installation costs for offshore wind installation projects helps to be cost-competitive with other renewable energy technologies. Installation costs can increase when the installation project planning is delayed. Literature shows that offshore wind installation projects are delayed by weather conditions exceeding operational limits and downtime caused by vessels and equipment. However, the magnitude and causes of downtime due to equipment breakdown are unclear. Additionally, no method is found in the literature to reduce downtime due to equipment breakdown in offshore wind installation. Data-analysis of observed failure data shows that equipment breakdown causes downtime during pinpile installation during the spring and summer seasons. Root-cause analysis indicates that scheduled preventive maintenance is often postponed on the critical path when weather conditions are favourable for installation. These decisions are made based on knowledge of oil and gas projects, but that knowledge is not applicable anymore. In this study a new method is proposed, which includes equipment characteristics and preventive maintenance on the critical path of an installation schedule, using discrete-event simulation (DES). In the DES model, four designs are simulated to gain insight into the effect of decision-making on the critical path on key performance indicators. The designs are based on the planned maintenance pillar of the Total Productive Maintenance framework. Implementing equipment breakdown and preventive maintenance in the installation schedule gives insight into the effects of decision-making before project execution. The results of this study indicate that the downtime due to breakdown and preventive maintenance of the hammer can be reduced by 10% if preventive maintenance is prioritized on the critical path.