page_title: Tidal stream generator
section_title: Axial turbines
hierarchical_section_title: Tidal stream generator / Types of tidal stream generators / Axial turbines
caption_attribution_description: Artwork illustrating cable tethered mounting system for tidal turbine
context_page_description: A tidal stream generator, often referred to as a tidal energy converter, is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.
  Tidal stream generators are the cheapest and the least ecologically damaging among the four main forms of tidal power generation.
context_section_description: These are close in concept to traditional windmills, but operating under the sea. They have most of the prototypes currently operating, including:
  Tocardo, a Dutch-based company, has been running tidal turbines since 2008 on the Afsluitdijk, near Den Oever. Typical production data of tidal generator shown of the T100 model as applied in Den Oever. Currently 1 River model (R1) and 2 tidal models (T) are in production with a 3rd T3 coming soon. Power production for the T1 is around 100 kW and around 200 kW for the T2. Tocardo were declared bankrupt in 2019. 
  The AR-1000, a 1MW turbine developed by Atlantis Resources Corporation that was successfully deployed at the EMEC facility during the summer of 2011.  The AR series are commercial scale, horizontal axis turbines designed for open ocean deployment. AR turbines feature a single rotor set with fixed pitch blades. The AR turbine is rotated as required with each tidal exchange. This is done in the slack period between tides and held in place for the optimal heading for the next tide. AR turbines are rated at 1MW @ 2.65 m/s of water flow velocity.
  The Kvalsund installation is south of Hammerfest, Norway. Although still a prototype, a turbine with a reported capacity of 300 kW was connected to the grid on 13 November 2003.
  Seaflow, a 300 kW Periodflow marine current propeller type turbine was installed by Marine Current Turbines off the coast of Lynmouth, Devon, England, in 2003. The 11m diameter turbine generator was fitted to a steel pile which was driven into the seabed. As a prototype, it was connected to a dump load, not to the grid.
  In April 2007 Verdant Power began running a prototype project in the East River between Queens and Roosevelt Island in New York City; it was the first major tidal-power project in the United States. The strong currents pose challenges to the design: the blades of the 2006 and 2007 prototypes broke and new reinforced turbines were installed in September 2008.
  Following the Seaflow trial, a full-size prototype, called SeaGen, was installed by Marine Current Turbines in Strangford Lough in Northern Ireland in April 2008. The turbine began to generate at full power of just over 1.2 MW in December 2008 and is reported to have fed 150 kW into the grid for the first time on 17 July 2008, and has now contributed more than a gigawatt hour to consumers in Northern Ireland. It is currently the only commercial scale device to have been installed anywhere in the world. SeaGen is made up of two axial flow rotors, each of which drive a generator. The turbines are capable of generating electricity on both the ebb and flood tides because the rotor blades can pitch through 180˚.
  A prototype semi-submerged floating tethered tidal turbine called Evopod has been tested since June 2008 in Strangford Lough, Northern Ireland at 1/10 scale. The UK company developing it is called Ocean Flow Energy Ltd. The advanced hull form maintains optimum heading into the tidal stream and is designed to operate in the peak flow of the water column.
  In 2010, Tenax Energy of Australia proposed to put 450 turbines off the coast of Darwin, Australia, in the Clarence Strait. The turbines would feature a rotor section approximately 15 metres in diameter with a slightly larger gravity base. The turbines would operate in deep water well below shipping channels. Each turbine is forecast to produce energy for between 300 and 400 homes.
  Tidalstream, a UK-based company, commissioned a scaled-down Triton 3 turbine in the Thames. It can be floated to its site, installed without cranes, jack-ups or divers and then ballasted into operating position. At full scale the Triton 3 in 30-50m deep water has a 3MW capacity, and the Triton 6 in 60-80m water has a capacity of up to 10MW, depending on the flow. Both platforms have man-access capability both in the operating position and in the float-out maintenance position.
  European technology and innovation platform for ocean energy (ETIP OCEAN) Powering homes today, Powering nations tomorrow report 2019. makes note of record volumes being supplied throu
caption: A cable tethered turbine
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