Tidal turbines are very much like underwater windmills except the rotors are driven by consistent, fast-moving currents. The submerged rotors harness the power of the marine currents to drive generators, which in turn produce electricity. Water is 832 times denser than air and consequently tidal turbine rotors are much smaller than wind turbine rotors and therefore can be deployed much closer together and still generate equivalent amounts of electricity.
Tidal turbines are fixed to the seabed either via a gravity base or fixed (drilled) pylons. They are connected to the grid via an armoured power export cable and are typically controlled via a standard SCADA system. Our tidal turbines have active pitch and yaw and can be installed quickly offshore, once the foundations are established on the seabed.
A typical turbine has an operational life of 25 years, with a 5 year maintenance cycle.
The Atlantis turbine division is the amalgamation of two of the world’s leading tidal turbine generation teams – the Marine Current Turbines (MCT) SeaGen team and Atlantis AR1500 team – brought together via acquisition in 2015. As a result, we have two turbine systems currently available for sale, the 1.5MW AR1500 system designed by Lockheed Martin Corporation and the 1.5MW SeaGen U turbine originally designed by Siemens Plc.
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What is a tidal turbine?
Marine or tidal currents, unlike many other forms of renewable energy, are a consistent source of kinetic energy caused by regular tidal cycles influenced by the phases of the moon. Intermittency is a problem for wind, wave and solar power as the sun doesn’t always shine and the wind doesn’t always blow. These sources of renewable energy often require backup from traditional forms of power generation. However, the inherent predictability of tidal power is highly attractive for grid management, removing the need for back-up plants powered by fossil fuels. Tidal turbines are installed on the seabed at locations with high tidal current velocities, or strong continuous ocean currents where they extract energy from the flowing water.
How it Works
The unique design of subsea connection systems for the AR1500 and SeaGen turbines allows capture of the maximum amount of tidal energy whilst keeping maintenance and connectivity costs low. Unlike a wind turbine, all of the power conditioning equipment (inverters, converters and frequency controllers) are located onshore in the substation building, enabling quick and easy access in the event of unscheduled faults.
Once a foundation has been established on the seabed floor, a turbine can be installed in a very short amount of time. Typically, it takes 45 minutes to install a turbine nacelle and 45 minutes to retrieve it. No divers are involved in this operation.
The AR1500 is a Lockheed Martin designed, 1.5MW horizontal axis turbine complete with active pitch and yaw capability. The nacelle weighs approximately 150 tonnes in air and has a design life of 25 years. The rotor diameter is 18 meters and all key operational systems have triple redundancy built in to maximise reliability offshore.
SeaGen U is a 1.5MW horizontal axis turbine complete with an active pitch system taken from the SeaGen-S series development, and yaw capability from the AR1500. The full turbine weighs approximately 150 tonnes in air and has a design life of 25 years. The rotor diameter is 20 meters and all key operational systems have redundancy built in to maximise reliability offshore.
The SeaGen system designed for floating or surface piercing foundations is an up to 1.0MW horizontal axis turbine complete with an active pitch. The full turbine weighs approximately 100 tonnes in air and has a design life of 25 years. Rotor diameter can be provided to suit the deployment and system redundancy plus accessibility combine to maximise reliability offshore.
Find out more about the history of our technology.
How are tidal turbines attached to the seabed?
AR1500 and SeaGen turbines are affixed to the seabed using either gravity based foundations, drilled monopiles, or pinned structures, depending on the local seabed topography and geotechnical conditions.
Operations and maintenance
AR1500 and SeaGen turbines have been designed for retrieval once every six years for an overhaul and maintenance program which should take approximately two weeks. A standard DP2 vessel can be used to retrieve the nacelles and return them to base for these programmed maintenance activities. Both systems have on board health monitoring systems to assist maintenance crews in planning future maintenance campaigns. Each field of turbines is monitored 24/7 and is controlled remotely via a standard SCADA system. Data collected from each turbine can be used for fault diagnosis, proactive maintenance planning and to improve turbine and array performance.