Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Numerical Study on the Self-installation of a Triple-column Spar Floating Wind Turbine Concept
Yan Gaoa,b, Jin Wangc,d, Liang Lie,fc.

a.

Qingdao Innovation and Development Center of Harbin Engineering University, Qingdao, Chinab.

State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, China

School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, China
d.
e.

f.

COTEC Offshore Engineering Solutions, Houston, Texas, USA
College of Engineering, Ocean University of China, Qingdao, China

Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, Glasgow, UKABSTRACTINTRODUCTION

Spar-type floating wind turbine foundations have been deployedsuccessfully for deep-water offshore wind power generation using theconventional installation method involving horizontal wet-tow of thehull and a large floating crane vessel for lifting the wind turbine towerand rotor system onto the hull. Due to the high cost and limited
availability of large floating crane vessels, offshore installation has been
identified as one of the key areas for technical innovation in order toreduce overall cost and schedule for large scale commercially viable
development of deep-water floating wind farms.
In this study, a novel self-installation method for installing a new concept
triple-column Spar floating wind turbine system is proposed, which not
only accelerates the installation process, but also drastically reduces theassociated cost. By employing the self-installation method, the windturbine tower and rotor system, the Spar deck structure and hull,consisting of three individual columns connected to a soft tank at the keel,
are initially connected upwards in installation configuration inshore at
the quayside, and subsequently wet towed offshore with the assistanceof reusable temporary stability modules. Once arriving at the deep-water
wind farm site, the Spar hull is first lowered to certain depth freely undergravity with the wind turbine tower mounted on the deck structure
connecting to the stability modules. The operating draft is achieved byadding ballast water into the hull columns, and at this point the deck
structure is then permanently connected to the hull. Feasibility study ofthe proposed self-installation method is carried out by simulating the
dynamic response of a 5MW triple-column Spar-type floating windturbine over the self-installation process. Simulation results indicate theinstallation process can be completed successfully thus proving thetechnical feasibility of the self-installation method preliminarily. The
next step will be to perform model tests to further investigate and validate
the triple-column Spar concept and the self-installation process.

The rapid growth of global demand boosts the large-scale exploitation ofoffshore wind energy resource. To meet the goal of Net Zero Emission
by 2050, the offshore wind sector is starting to generate renewableenergy in deep water zone, where the wind resource is of higher quality.
New installation challenge arises in the meanwhile, as floating structure
must be employed to carry the wind turbines.
Among various types of offshore floating structure, the Spar has been
widely employed. The world’s first floating wind turbine concept
Hywind demo adopts the Spar structure to support a 2.3 MW windturbine (Equinor, 2017). The first floating wind farm in the world,Hywind Scotland (Equinor, 2021), is also based on the Spar solution.
The deep draft feature of Spar makes itself subjected to less wave load,
which partially explains the popularity of Spar structure. However, thetransportation and installation of Spar is very challenging. As a result of
the deep draft, Spars are typically towed horizontally and then upended
to vertical position through ballasting. It indicates that the wind turbine
must be transported separately, and then assembled to the Spar structurein the ocean with the assistance of a large crane vessel. Not only theinstallation cost is increased, but also extra challenges arise. As pointed
by Jiang et al. (2018b), the hydrodynamic and mechanical interactions
make the analysis of multibody dynamics extremely difficult.
Researchers have attempted to overcome these installation challenges bydeveloping specialized equipment. Jiang et al. (2020) designed andnumerically analyzed a large floating dock, which was specificallydeveloped for Spar floating wind turbine installation. Their concept
reduced potential installation risk by shielding the Spar. Sarkar andGudmestad’s method (Sarkar and Gudmestad, 2013) was based on a
floating installation vessel along with a floatable subsea structure.

KEY WORDS: self-installation; floating wind turbine; triple-column
Spar.

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