The floating buoyant structure

The floating buoyant structure ("the Buoy") is a series of stiffened carbon steel shell tubular sections of varying diameters. These sections form a column or spar, narrow at the surface, with a wide Buoyant Equipment Chamber (BEC) below the surface.

The BEC is the main equipment space, provides the attachment points for the tether system and provides support for the control and monitoring of umbilicals. It is 10 metres in diameter, and is compartmentalised by watertight horizontal decks and vertical steel bulkheads into a number of internal deck sections, each of which is accessed through a watertight hatch:

In the following example, there are 5 decks which have been configured to support the main operation as a power buoy. Other configurations are possible and can be discussed based on requirements and budgets.

• Deck 1: Control and LV electrical distribution deck - this level houses the main control and communications systems together with low voltage electrical distribution and bulk consumables (lubricating oil and cooling water top-up) storage. It is divided into three watertight compartments.
• Deck 2: Combined generator deck 1 - this level houses three 820 kWatt diesel-driven generators and ancillary systems (cooling, batteries, silencers, filtration etc.).
• Deck 3: Combined generator deck 2 - this level is similar to Deck 2.
• Deck 4: Variable Speed Drives (VSD) deck - this level houses 8 working and 1 spare Variable Speed Drives for powering and controlling 8 sub-sea Electric Submersible Pumps (ESPs). In addition to this, medium voltage switchgear is located at this level.
• Deck 5: Diesel storage deck - this level houses emergency diesel fuel supply suitable for 10 days' operation of the facility together with diesel transfer pumps and coalescers.

The BEC starts approximately 12 metres below the surface, and continues to a depth of approximately -25 metres LAT.

Access into the BEC is provided through a Central Access Shaft (“CAS”). The CAS is 3.00 metres in diameter and extends from Deck 4 to a boat landing deck positioned c. 6 metres above water level, and which allows safe access to the Buoy for maintenance visits. Access to the Buoy can be by fast rescue craft or dynamically-compensated gangway.

Attached to the CAS is a 1.44m tubular mast section, which rises to c. 23 metres above water level which supports: 

• Two working platforms - an upper and lower platform - which allow access to navigation, communication and safety equipment; and
• Generator exhausts, air intakes and ventilation filters.

An access ladder - which includes a fall arrest safety system - runs up the mast