Development of tidal stream generators

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.

Lots of different technology variants have been tested, and there has not been convergence on a predominant typology. Most have been horizontal-axis, like wind turbines, but with 2, 3, or more blades and either mounted on a seabed fixed foundation or on a floating platform. In addition, vertical-axis turbines and tidal kites are also being developed.

Historically, development has largely been focused around Europe, but devices have been built and tested in North America – including at the Fundy Ocean Research Centre for Energy (FORCE), Japan, and elsewhere. The European Marine Energy Centre (EMEC) was set up in Orkney in 2003, and developed a tidal test site in the Fall of Warness, to the west of the island of Eday. The site opened in 2006, and EMEC was granted a license in 2016 to test up to 10 MW of tidal stream devices, and has since hosted the testing of many of these devices.[1]

There have been various acquisitions of technology developers over the years. Many of the companies are no longer trading, or have ceased development of tidal-stream turbines. However, the first pre-commercial array demonstration projects have been operating since around 2016. Building on this, commercial arrays are expected to be operational by around 2027, at EMEC, Morlais and elsewhere.

Development timeline

Key historical milestones in the development of tidal-stream turbines are summarised below:

• The 300 kW Marine Current Turbines (MCT) SeaFlow turbine was installed in summer 2003 and tested off the coast of Lynmouth, Devon, England.[2]
• In 2004, the world's first tidal-stream turbine was connected to an electricity grid, the 300 kW Hammerfest Strøm HS300, located in the waters of Kvalsundet, Finnmark, Norway.[3]
• The first tidal stream turbine test site was constructed in 2005 and opened in 2006, in the Fall of Wanress to the west of Eday, Orkney, part of the European Marine Energy Centre.[1]
• The significantly more powerful, 1.2 MW MCT SeaGen turbine was installed in Strangford Lough, Northern Ireland, in May 2008 and grid connected in July.[4]

Key companies and turbines

Many companies have focused on the development of technology to harness tidal stream energy. A non-exhaustive list of key companies is given below.

List of grid-connected tidal stream generators

Over the years, many different tidal stream turbines have been deployed and tested at sea, and have delivered power to the local electricity grid. A non-exhaustive list is given in the table below, along with other notable devices. As most of these were development and test versions, they were removed for periods of time for maintenance or upgrades.