Installation of Monopile Substructures on Offshore Wind Farms – A Case Study

Abstract Monopiles are large-diameter tubular steel foundations used to support offshore Wind Turbine Generators (WTGs) and transfer structural loads to the seabed. Development of Offshore wind farms began in the early 1990s with small 450–750 kW turbines having ∼40–50 m rotor diameters and short monopiles of ∼3–4 m diameter in shallow waters. By the mid-2000s, commercial projects deployed 2–3 MW turbines with ∼80–100 m rotors and monopiles growing to ∼4.5–5 m. In the 2010s, rapid scale-up led to 6–8 MW turbines with 150–170 m rotor diameters, while monopile diameters reached 6–7 m to support larger loads and deeper installations. By the late 2010s and early 2020s, the industry moved to 10–12 MW turbines with 200–220 m rotors and monopiles expanding to 8–9 m, weighing over 1,500–2,000 tonnes. Today, offshore wind is in a mega-turbine phase, with 14–18 MW models entering commercial rollout, rotor diameters reaching 240–270 m, and XL monopiles exceeding 10–11 m diameter and 3,000–4,000 tonnes. Floating wind is also progressing from demonstration to early commercial stage, enabling >50–60 m water depths and supporting 15–20 MW turbines. The traditional use of jack-up vessels (JUVs) has become increasingly challenging as wind farm developments move into deeper waters and monopile sizes continue to grow. In such conditions, floating installation vessels become the preferred and only feasible option. Correspondingly, the scale and complexity of the required installation equipment also increase. This paper presents a case study of the installation of 65 monopile foundations in the Far East Asia region, covering an area of approximately 100 km in early 2030s. Water Depths (WD) ranged from 7 m to 35 m, and monopile lengths varied between 65 m and 95 m with the heaviest monopile weighing 1950 mt. The design of the monopiles included the Transition Pieces (TPs) which was grouted to the monopiles. However, the installation of these TPs and associated super structures above were executed by other installation contractors. In cases where a specific Wind Turbine Installation Vessel (WTIV) is not available to the EPC contractor, the assessment of installation tools, vessel selection, and operational methodologies for monopile installation using their heavy lift floating vessels requires detailed planning and engineering. This paper also describes the specialized equipment employed, outlines comprehensive installation procedures, and provides insights into the engineering practices necessary for the successful installation of wind turbine foundations. It is intended to serve as a valuable reference for EPC contractors seeking to expand into offshore wind farm projects.