Technology Readiness Level (TRL) Study of New Offshore Wind Turbine Foundations
Creators: name: ALEEM, MUHAMMAD
Publisher: name: University of Surrey
Year: 2022
Subjects: Offshore wind
Monopile
Collared
Soil-Structure Interaction
Gravity Based Foundation

description: Offshore wind power is becoming an affordable form of clean energy that will positively
description: affect the environment. Modern-day wind farm is a collection of Wind Turbine Generators
description: (WTG), and the majority of currently installed are supported on a single large diameter pile
description: (commonly known as monopile). Foundations for an offshore wind turbine is one of the most
description: expensive components (typically costs between 16 and 34% of the overall cost). The analysis,
description: design and construction of the foundation of these structures require multidisciplinary
description: knowledge. In order to reduce the cost of wind power, there has been extensive research to
description: find new types of foundations. Naturally, for such novel/new foundations, codes of practice
description: for design will not be fully developed. Due to technological innovations, the sizes of turbines
description: (rated power and RNA mass) are increasing. As offshore wind turbines are being planned to
description: be installed in deeper waters, customised or non-standard foundations are necessary.
description: Furthermore, offshore wind turbines are also sited not only in deeper waters but also in
description: seismic areas and disaster-prone areas (typhoons and hurricanes). To satisfy the industry
description: requirements and de-risk the installation and operation, any new foundation must be validated
description: through a structured study of the Technology Readiness Level (TRL). This thesis developed
description: techniques to study different aspects of TRL studies for new foundations with a super focus
description: on the long-term performance of foundations.
description: TRL studies have been carried out for gravity-based foundations and hybrid foundations. By
description: hybrid foundations, it is meant that foundations have aspects of shallow and deep foundations,
description: i.e., where loads will be transferred to shallow layers (shallow foundations) and deeper layers
description: (deep foundations). Hybrid foundations can be attractive in many situations: ground having
description: shallow rock, to reduce the diameters of monopile before it becomes too large to handle and
description: finally to avoid tilting. Different forms of hybrid foundations are studied using a numerical
description: and physical modelling approach. To understand the effectiveness of a hybrid foundation, the
description: comparison is made with monopile alone. One particular hybrid foundation is studied in more
description: detail: Combination of a caisson and a monopile named Collared Monopile. It was found that
description: the stiffness of a Collar Monopile foundation depends on the stiffness of the collar and
description: monopile and the surrounding soil. Due to the addition of the collar, the reserve strength and
description: stiffness of the overall hybrid foundation increases; therefore, the risk of long-term tilt can be
description: better engineered. A novel approach is proposed to analyse the concept of a hybrid
description: foundation.
description: Gravity-based foundations are becoming an attractive option for shallower water depths. A
description: simple integrated method within the so-called “10 Step method” is developed to find the initial
description: size of the foundation.
description: Monopile design is dominated by the pile head stiffness and is required for SLS
description: (Serviceability Limit State), natural frequency estimation and long-term tilt calculations.
description: Estimating load carrying capacity (combined effect of moment and lateral load) is needed to
description: optimise monopile and long-term tilt calculation. Long term tilt needs a LU (Load Utilisation)
description: ratio, which is the ratio of applied load to the load-carrying capacity. The thesis also analyses
description: the LU ratio for many European Wind Farms based on minimum data. It is hoped that these
description: calculations will support a quick preliminary design process. Finally, future suggested works
description: are also provided.