Bauma Innovation Prize 2013 - Construction Engineering Techniques category: BAUER Spezialtiefbau GmbH - Drilled Monopile Foundation for a Tidal Turbine

A number of BAUER Group companies were involved in a project in the summer of 2011 to install a monopile into the sea bed as the foundation for a tidal turbine. The contract was executed by BAUER Renewables Ltd. with the help of its parent Bauer Spezialtiefbau GmbH.

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Tidal flows are a good source of renewable energy, as they provide a regular and predictable output. In the North Sea off Scotland, close to the Orkney Islands, a test field of the European Marine Energy Centre (EMEC) has been established for such projects aimed at generating renewable energy.

In order to install the monopile foundation, Bauer's engineers designed an entirely new drilling rig which is lowered to the sea bed and is operated hydraulically from on-board a floating vessel. The new rig was designed by Bauer Maschinen, and within just a few months was ready for operational use. Its name: the BSD 3000 – BSD standing for Bauer Seabed Drill. Initial sketches were produced in October 2010, and in March 2011 manufacturing of the rig began. In the subsequent phase the project was subject to strict timing constraints. Every day was planned exactly: for testing, transportation from Hamburg to the UK port, transfer from the port of Scrabster to the drilling location, and for the drilling phase itself.

The work on-site had to take account of the tides, waiting for the hour or two in which ebb turned to flood and vice versa. Only during that period of relative calm was it possible to lower the key components of the rig: the drilling template with casing oscillator, guide casing and drilling tool. The actual drilling was possible even when the sea was rough. The special ship was held in position by a propulsion system based on GPS.

Thanks to detailed preparation, the drilling operation ran almost perfectly. The drilling was carried out using a full-face roller bit with heavy weights. The cuttings were transported to the surface by an air-lift system. The torque was provided by a modified BG 28 rotary drive. At a depth of around 37 meters underwater, a 23 metre long monopile with two metre diameter was grouted into an 11 metre deep rock socket with high-strength mortar. The one megawatt turbine will be installed approximately 12 metres above the sea bed – a depth at which it is able to make optimum use of the tidal flows.