As part of the endorsement process with DNV-GL, Hann-Ocean will be measuring “pure” wave profiles generated in the “Hann-Ocean 01” wave tank, with the existing Drakoo-B0015 WEC removed from within. To that end, the team at Hann-Ocean Energy and Technology, Nantong (HOENT) prepared a detailed lifting plan and executed the complex operation well in advance of the original schedule

Challenges

Measuring 5m x 3.5m x 3m, the WEC was installed in the 6m deep by 4m wide wave tank in 2016 and has remained in place for the last 2.5 years. The actual available clearance (in the order of a few mm) between the hull and the tank walls had to be determined to avoid collisions over the entire 5m height of the device. To compound this problem, the operation was carried out using the company’s two overhead cranes working in tandem to lift and move the device laterally out of the wave tank in a fairly limited vertical space.

Execution

Hann-Ocean has developed and perfected a procedure for lifting the power take-off system (PTO) of the WEC. Cables, fences, cameras and other accoutrements on the viewing platform were removed as part of the preliminary work, following which the PTO system was hoisted and placed on specially fabricated brackets. Computer simulations of a 4-point lifting arrangement on the WEC’s front and rear were performed to study the lift, translation and landing of the device’s hull on the workshop floor. Prior to the actual lift, video equipment was set up to monitor the operation from different angles and the M.D., Mr Henry Han, oversaw the process from Singapore. Project Manager, Ling Zedong handled the cranes with the assistance of three members and the operation was completed in 1.5 hours. Despite working overtime, the team members maintained their poise throughout this delicate procedure which made for a smooth and efficient operation. Wave tank measurements for DNV-GL and maintenance work on the hull will be carried out simultaneously, following which the WEC will be reinstalled in the tank and will continue demonstrating its capability to Hann-Ocean’s partners and customers.