Conference programme

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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Carlos Wong CBJ Ocean Engineering Corp., China
Co-authors:
Carlos Wong (1) F Wiktor Wasilewski (1) P Chris Yiu (1)
(1) CBJ Ocean Engineering Corp., Beijing, China (2) Structural Engineering Integrated P.C., New York, United States

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Dr Carlos Wong graduated with a PhD from the University of Dundee, Scotland 1983, and immediately returned to the industry as a practicing engineer whose works range from marine to highways and to bridges. The latter becomes his specialty. His latest projects include 38km Hong Kong - Macau - Zhuhai Bridge and the world 2nd longest span cable stayed Stonecutters Bridge, the 5th longest span Sutong 2nd. After retired from Arup in 2012, he established an engineering firm CBJ Ocean Engineering Corp in China concentrating on ocean platform that could replace traditional reclamation. The firm has produced some unique patented technologies that enable the platform to becoming competitive, and the patent pending offshore wind turbine carrier.


Poster

Poster Download poster (7.34 MB)

Abstract

A self-orientated Semi-Submerged Concrete Multi-Turbine Platform Wind Power Generation Unit

Introduction

This paper is a continued development of the latest break-through technology [1] posted in EWEA OFFSHORE 2015 - about a semi-submerged concrete raft platform supporting 3-turbines (triangle) and 5-turbines (trapezoid) that turns towards the coming wind automatically by wind force,without complicated electric-mechanical device. The whole platform completed with turbines are assembled in a harbour and towed to the site. After the mooring lines to the seabed mass anchor and connect the power cable are connected, the unit is ready to work. The construction, installation and maintenance costs are expected to be much lower than existing offshore options.

[1] Wong, C. Wind Tracing rotational semi-submerged raft for multi-turbine wind power generation, EWEA OFFSHORE 2015 Conference, Copenhagen, March 2015.

Approach

The approach is leaving the existing options behind and think independently the new setup, the problems of single turbine’s rolling and pitching movements, the grouping problems of several turbines together of which the air wakes question, the very long beams in the water, the turning mechanism. In the paper [1] the solutions are to link several turbines together in a platform in close spacing, and as long as the platform turns to the changing wind direction the turbines catch the maximum wind power without interference by air wake between the grouped turbines. Bridge building techniques are referenced in the design and construction platform raft structure.

Main body of abstract

A 3-turbines 3-beams triangle, and a 5-turbines 7-beams trapezoid rafts are considered. The 2.2D length beams, where D is the turbine rotor diameter, are hollow and are located at sufficient depth (>14m) so that waves have little effects on them. One important aspect of the system is that the raft beams are in suspension state without stressed, i.e., the buoyancy is balanced by self weight. The beams meet at the triangle/trapezoid vertex formed by a concrete hollow floater on which a turbine is erected. The floaters provide the sole buoyancy to the system. The function of the beams is to restrain the turbines from moving individually so as to restrain the turbine’s rolling and pitching. Therefore, the beams should have sufficient stiffness. Concrete box section provides the necessary stiffness with sufficient weight to balance the buoyancy whereas heavy ballast has to be employed for steel section. The platform has very small waterplane area (the floater cross section areas) but on a very large footprint hence, the platform is very stable. This is demonstrated by a 1/500 model test under natural wind conditions presented in this paper.

The turning mechanism is formed by attaching each floater bottom with a cable line/wire and all cable lines merge into one point below the platform and offset from the CG. The merge point is the turning point to which a mooring line is attached. A single point mooring is used so that the raft can turn. The remaining problems are the power cable. If an electric coupling turret is used, then problems solved. Without the turret, a cable breaker is used to break the cable when the turbines are not generating power. This will release the twisting of the power cable under working condition when the breaker is in closed position. In the present paper, the whole system is reviewed, with added study of the power cable breaker relating to cable twisting, and mooring study.

Conclusion

We believe that the gate to far shore wind power is now opened with the new concrete semi-sub raft supporting multi-turbine with price tag not higher than existing or even lower. However, more research works on its analysis and design are needed.


Learning objectives
The delegates are refreshed with a new promising technology for floating wind farms. The new technology may change the direction of the industry from fixed bottom foundation in nearshore to floating option in the farshore.