Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods.
The Pelamis Wave Energy Converter was a technology that used the motion of ocean surface waves to create electricity. The machine was made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity.
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 production of renewable energy in Scotland is a topic that came to the fore in technical, economic, and political terms during the opening years of the 21st century. The natural resource base for renewable energy is high by European, and even global standards, with the most important potential sources being wind, wave, and tide. Renewables generate almost all of Scotland's electricity, mostly from the country's wind power.
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.
Muckle Green Holm is an uninhabited island in the North Isles of the Orkney archipelago in Scotland. It is roughly 28 hectares (0.11 sq mi) in extent and rises to 28 metres (92 ft) above sea level, the summit having a triangulation pillar.
Renewable energy in the United Kingdom contributes to production for electricity, heat, and transport.
The European Marine Energy Centre (EMEC) Ltd is a UKAS accredited test and research center 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.
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.
SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation. It was decommissioned by SIMEC Atlantis Energy Limited in summer 2019, having exported 11.6GWh to the grid since 2008.
Marine Current Turbines Ltd (MCT), was a United Kingdom-based company which 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.
Evopod is a unique tidal energy device being developed by a UK-based company Oceanflow Energy Ltd for generating electricity from tidal streams and ocean currents. It can operate in exposed deep water sites where severe wind and waves also make up the environment.
The Oyster was a hydro-electric wave energy device that used the motion of ocean waves to generate electricity. It was made up of a Power Connector Frame (PCF), which is bolted to the seabed, and a Power Capture Unit (PCU). The PCU is a hinged buoyant flap that moves back and forth with movement of the waves. The movement of the flap drives two hydraulic pistons that feed high-pressured water to an onshore hydro-electric turbine, which drives a generator to make electricity. Oyster was stationed at the European Marine Energy Centre (EMEC) at its Billia Croo site in Orkney, Scotland until the company ceased trading in 2015.
A tidal farm is a group of multiple tidal stream generators assembled in the same location used for production of electric power, similar to that of a wind farm. The low-voltage powerlines from the individual units are then connected to a substation, where the voltage is stepped up with the use of a transformer for distribution through a high voltage transmission system.
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 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.
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.
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.
