Babcock’s innovative floating Light Detection and Ranging (LiDAR) system to provide critical meteorological data for offshore wind farm developers at reduced cost, has been deployed to start a six month trial of the new system in the Irish Sea.
The floating LiDAR system is being trialled at RWE’s Gwynt y Môr offshore wind farm, off the north Wales coast, where it is positioned next to the fixed meteorological mast to enable comparison of information with that from the fixed mast, as part of a detailed independent assessment of the system.
Babcock’s floating platform LiDAR system is a low motion shallow draft spar buoy, and is one of a new breed of technological improvements for the offshore wind sector. It has been designed with low motion characteristics to enable accurate, high quality wind measurement data to be obtained without the high costs associated with fixed platform construction for mast installation (which typically costs several million pounds, increasing as developers move further offshore into deeper water). The current trial of Babcock’s system is part of the Offshore Wind Accelerator (OWA) programme focused on reducing the cost of offshore wind power, promoted and co-ordinated by the Carbon Trust.
Wind data including velocity and direction is critical to windfarm planning, development and operation. LiDAR systems (which measure wind speed and direction by comparing the light from a laser beam, reflected by microscopic dust particles in the atmosphere, to a reference light source) cannot provide accurate data if subjected to high levels of motion. This presents technical challenges that have to date limited the use of such measurement and monitoring sensors offshore.
Babcock’s floating LiDAR system (unlike many other such developments, where some form of motion compensation or post-processing of data occurs) has been designed to address the motion issue simply by designing it to within an acceptable level of pitch and roll motion, which the Zephir LiDAR system can accommodate, to facilitate reliable and accurate measurement of wind speed, direction and turbulence. Babcock has also developed an integrated power (supplied by photovoltaic panels and micro wind turbines installed on the buoy) and communication system to facilitate remote, autonomous operation of the system, reducing the need for regular visits to the platform. Additionally, the platform’s stability also makes for safer access and working onboard when routine six-monthly maintenance visits are made.
Deployment of the system for the trial was achieved using a combination of a crane barge (carrying the buoy) and a work cat to tow the system to the RWE Gwynt y Môr trial location site, where it was connected to the tri-catenary mooring system, comprising three mooring lines and three 15 tonne steel anchors to provide the required weight to keep it in position. The whole installation process was carried out without the need for any diving activity, with minimum risk and maximum safety. Commissioning was then carried out by Babcock personnel fully trained to work both offshore and at height.
During the course of the trial, Babcock will be exploring opportunities to further reduce the cost of deployment and recovery without compromising safety, with the design of a barge-mounted lifting frame which can be used in shallow draft ports throughout the UK, so that no specialist vessels (only work cats and readily available barges) will be required.
Following the current trial, future developments (for which the buoy has been designed) will include the ability to deploy a range of sensors and equipment to measure further key factors, beyond meteorological data alone, including wave and tidal activity, and marine mammal and bird monitoring. The buoy has been designed to provide a stable platform for such environmental, meteorological and metocean data measurement.
Babcock programme manager Liam Forbes said: “The deployment of our floating LiDAR system for this six month trial is key to proving the viability of our low motion buoy as an effective stable platform for the reliable and accurate recording and analysing of local wind conditions. This will then allow us to undertake further development to incorporate additional measurement and monitoring equipment.
He continued: “The ability for offshore windfarm developers and operators to use a floating platform for meteorological monitoring and information gathering in preference to a fixed one, to retain reliable and accurate data, will help to drive down both construction and through-life costs for the windfarm, and will also be a valuable contribution to the development of the next generation deep water sites.“
Press release, July 19, 2013; Image: KEEPINTOUCH