Minimising oscillations of floating off-shore platforms.

Kurzfassung

A Greek spin-off company has developed a stable floating platform, which maintains its stability regardless of wind speed and wave conditions. The platform is tested in the Aegean sea in a floating desalination plant. They are seeking industrial partners with the appropriate engineering expertise and facilities to conclude a licensing agreement or commercial agreement with technical assistance or to perform scaling up of the unit under a joint venture agreement.

Details

A lot of marine applications are based on the development of floating structures, which must remain stable in the sea with all the required equipment for the implementation of various activities installed on board.

The most common floating structures consist of a platform, which is supported on floaters (buoys). These floaters provide the required buoyancy and the suitable stability of the platform so that it and the installed equipment float on the sea. The existing technology concerns mainly structures that are either supported on the seabed, or are firmly tied up with strained chains and anchors in the seabed. The basic disadvantage of existing systems is the high cost of mooring (anchoring) and the difficulty (and increased cost) to move them to other areas. Also in other floating structures the crew has to increase the inclination in the event of bad weather conditions, in order to decrease distresses and improve the safety of the structure.

The spin-off company, created by the department of Shipping of a Greek University, has developed a stable floating platform for a wide range of waves and wind speeds.

The floating structure is constituted by one cylindrical central floater (buoy), four peripheral cylindrical floaters of smaller diameter connected to each other with tubes of small diameter that form a lattice. The central cylinder is big enough, so that it can accommodate equipment for various purposes depending on the use of the platform. The peripheral cylinders are made in such a way that they can store different water quantities. Stability is achieved with the controlled import and export of water mainly in the peripheral cylinders.

A control system is responsible for water importing and exporting in the peripheral cylinders, which increases and decreases respectively the mass of the cylinders, leading to changes of the platform's natural period. Thus the wave period determines the water intake at the peripheral cylinders, which consequently changes the natural period of the platform. This process ensures system's stability, by avoiding resonance between the platform and the sea waves and achieving the smallest oscillation possible. The level of water in the cylinders is adjusted dynamically and proportionally to the height of the wave so that the movements (oscillations) of the platform are further decreased.

The system has been tested under severe conditions in the Aegean Sea. With the appropriate equipment to become an autonomous, floating desalination plant (wind turbine, desalination unit, etc.) the system can float in harsh conditions (9 Beaufort wind speeds, 5 meter waves) with minimal oscillations.

The spin-off company is seeking industrial partners, with the appropriate engineering expertise and facilities for the scaling up of the unit under a joint venture, or the adoption of the technology under a licensing agreement or conclusion of a commercial agreement with technical assistance.

Innovative Aspects:
The design and control system of the floating platform suggested here is time and cost effective since the difficulty of mooring, anchoring and moving is significantly reduced.

The aforementioned platform can float on the sea or be easily towed to other places, because it only requires simple anchoring similar to that used by conventional marine vessels. Moreover the control of stability occurs automatically without human supervision.