Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods.
The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was developed in 1913 by Austrian professor Viktor Kaplan, who combined automatically adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over a wide range of flow and water level.
Marine currents can carry large amounts of water, largely driven by the tides, which are a consequence of the gravitational effects of the planetary motion of the Earth, the Moon and the Sun. Augmented flow velocities can be found where the underwater topography in straits between islands and the mainland or in shallows around headlands plays a major role in enhancing the flow velocities, resulting in appreciable kinetic energy. The Sun acts as the primary driving force, causing winds and temperature differences. Because there are only small fluctuations in current speed and stream location with minimal changes in direction, ocean currents may be suitable locations for deploying energy extraction devices such as turbines. Other effects such as regional differences in temperature and salinity and the Coriolis effect due to the rotation of the earth are also major influences. The kinetic energy of marine currents can be converted in much the same way that a wind turbine extracts energy from the wind, using various types of open-flow rotors.
The Gorlov helical turbine (GHT) is a water turbine evolved from the Darrieus turbine design by altering it to have helical blades/foils. Water turbines take kinetic energy and translate it into electricity. It was patented in a series of patents from September 19, 1995 to July 3, 2001 and won 2001 ASME Thomas A. Edison. GHT was invented by Alexander M. Gorlov, professor of Northeastern University.
Verdant Power, Inc is a maker and installer of tidal power and hydroelectric systems. Their primary device is an underwater turbine, similar to a three-bladed wind turbine, that is designed to capture energy from tidal currents and (precipitation-driven) river currents. The company uses the trade term "kinetic hydropower" to distinguish their systems from those based on dam construction. The company's first project, the Roosevelt Island Tidal Energy Project, is several turbines in New York City's East River.
The European Marine Energy Centre (EMEC) Ltd. is a UKAS accredited test and research centre focused on wave and tidal power development, based in the Orkney Islands, UK. The centre provides developers with the opportunity to test full-scale grid-connected prototype devices in wave and tidal conditions, at pre-consented test sites. EMEC also has sites for testing smaller-scale prototypes in more sheltered conditions.
A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where fixed-foundation turbines are not feasible. Floating wind farms have the potential to significantly increase the sea area available for offshore wind farms, especially in countries with limited shallow waters, such as Spain, Portugal, Japan, France and the United States' West Coast. Locating wind farms further offshore can also reduce visual pollution, provide better accommodation for fishing and shipping lanes, and reach stronger and more consistent winds.
Marine Current Turbines Ltd (MCT), was a United Kingdom-based company that developed tidal stream generators, most notably the 1.2 MW SeaGen turbine. The company was bought by the German automation company, Siemens in 2012, who later sold the company to Atlantis Resources in 2015.
A tidal farm is a group of tidal stream generators used for production of electric power. The potential of tidal farms is limited by the number of suitable sites across the globe as there are niche requirements to make a tidal farm cost effective and environmentally conscious.
A tidal stream generator, often referred to as a tidal energy converter (TEC), 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 the run of a 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.
The Paimpol–Bréhat tidal farm is a tidal stream turbine demonstration site, located northeast of Île-de-Bréhat near Paimpol, Brittany, France. It was initially developed by Électricité de France (EdF), initiated in 2004 and construction work began in 2008, but the project was subsequently cancelled by EdF in 2018. This project was to use OpenHydro turbines, with two briefly installed in 2016, but they were later removed.
Schottel is a manufacturer of propulsion and steering systems for ships and offshore applications. The company founder Josef Becker invented the rudderpropeller, a z-drive, in 1950. Today the company develops and manufactures azimuth propulsion, maneuvering and steering systems. In 2014 the subsidiary Schottel Hydro was founded to bundle up the company activities in the hydrokinetic energy segment.
MeyGen is a tidal stream energy plant in the north of Scotland. The project is located in the Pentland Firth, specifically the Inner Sound between the Island of Stroma and the Scottish mainland.
SAE is a renewable energy company. It is incorporated in Singapore, but its operational headquarters are in Edinburgh, Scotland, United Kingdom. Initially, it was a developer of the tidal power turbines and projects, but after becoming a part of GFG Alliance it has expanded its business also to the waste-to-energy and hydropower.
Morlais is a grid connected tidal stream energy project located in the Irish Sea just off the west coast of Holy Island, Anglesey, Wales. It is being developed by the social enterprise agency Menter Môn. The site has the potential for up to 240 MW of renewable energy to be harnessed from the tides, using a mixture of seabed mounted and floating tidal energy devices from different companies.
Nova Innovation Ltd is a Scottish developer of tidal stream turbines, based in Leith, Edinburgh. They deployed their first 30 kW turbine in 2014. Since then, they have developed and tested a 100 kW seabed mounded two-bladed horizontal-axis tidal stream turbine, and plan to scale this up in future. Up to six of these turbines have been deployed simultaneously in the Bluemull Sound, Shetland since 2016.
Many tidal stream generators have been developed over the years to harness the power of tidal currents flowing around coastlines. These are also called tidal stream turbines (TST), tidal energy converters (TEC), or marine hydro-kinetic (MHK) generation. These turbines operate on a similar principle to wind turbines, but are designed to work in a fluid approximately 800 times more dense than air which is moving at a slower velocity. Note that tidal barrages or lagoons operate on a different principle, generating power by impounding the rising and falling tide.
OpenHydro Group Ltd was an Irish developer of tidal stream turbines, established in 2004. It was acquired by Naval Energies in 2013, however, Naval Energies decided in July 2018 to stop developing tidal turbines and focus on floating wind turbines. The company subsequently went into liquidation with debts of about €280m.
Sabella SAS was a French company which developed and manufactured tidal stream turbines. It was a SME, founded in 2008, and based in Quimper, Brittany.
