The 1:20 scaled hydraulic model test and field experiment of barge-type floating offshore wind turbine system

Abstract

Objective of this study is to develop a barge-type floating offshore wind turbine (FOWT) in order to face extreme environmental conditions in western Taiwan offshore water area. The prototype of FOWT considered here consists of (1) NERL 5 MW wind turbine, (2) a single steel column with a hub height of 90 m above sea level, (3) a square barge-type floating platform equipped with a damping pool and heave plate to improve the stability of the floating foundation, (4) catenary mooring system using anchor chain, and installation at a water depth of 70 m in the western Taiwan offshore water area.In order to verify the feasibility of the concept, a 1/20 scale model of the FOWT prototype was used by conducting hydraulic model tests in the large flume (300m × 5m× 5m) at Tainan Hydraulics Laboratory (THL), National Cheng Kung University (NCKU) and field experiments at the Anping Harbor. Hydraulic model tests include (1) regular wave test, with normal wave period from 5.7sec to 8.9sec, and long wave period from 9 s to 14sec. (2) irregular wave test, including normal sea condition, northeast monsoon sea condition, ten-year return period typhoon wave condition, and 50-year return period typhoon wave condition. Moreover, investigation of wind speed, wind direction, wave height, dynamic motion of FOWT, mooring tension, and rotor speed were conducted in the field experiment.After examining the motion of the barge-type offshore floating wind turbine, it was found that the pitch and the roll motions could satisfy the DNV standard. The tension of the mooring line did not exceed the minimum breaking load (MBL), which indicating the good stability of the barge-type FOWT proposed by this study.