Tidal power is harnessed by converting energy from tides into electricity using various methods. While it’s not yet widely used, tidal energy has potential for future electricity generation because waves are more predictable than the sun and the wind.
Among renewable energy sources, tidal power has suffered from high cost and limited availability of sites with sufficiently tidal currents or flow velocities, thus limiting its total availability.
The O2 Turbine
On April 22, Scottish company Orbital Marine Power launched “the world’s most powerful tidal turbine,” the Orbital O2, from the Port of Dundee. Two days later, the 2MW tidal turbine arrived in the Orkney Islands, an archipelago of Scotland’s north-eastern coast and home to some of the strongest tidal currents in the world. In July, Orbital Marine Power announced that the O2 has officially started grid-connected power generation at the European Marine Energy Center in Orkney.
The O2 turbine is connected to the local onshore electricity network via an undersea cable. The entire contraption is anchored to the seafloor at four points and has a 1-MW turbine nacelle on either side of its 242-ft (74-m)-long hull, with 32-ft (10-m) blades capturing tidal energy over an area of more than 600 m2.
According to Orbital, the O2 turbine has an operational lifespan of approximately 15 years and can meet the annual electricity needs of roughly 2,000 homes. However, it is committed to delivering power to the European Marine Energy Center’s onshore electrolyzer to generate green hydrogen.
Andrew Scott, the CEO of Orbital, said:
This is a major milestone for the O2, and I would like to commend the whole team at Orbital and our supply chain for delivering this pioneering renewable energy project safely and successfully. Our vision is that this project is the trigger to the harnessing of tidal stream resources around the world to play a role in tackling climate change while creating a new, low-carbon industrial sector.
The Scottish Government and ethical investment platforms funded the construction of the O2 turbine. At the same time, the more comprehensive project received support from the European Regional Development Fund and the EU’s Horizon 2020 program. As a result, the company is currently scaling up operations with multi-MW installations, with costs expected to drop considerably as the technology is deployed.
Others Harnessing Tidal Power
The MeyGen tidal stream array, owned by Simec Atlantis Energy, is a tidal power plant in UK waters, just 2km from Scotland’s northeast tip. As of 2020, it had exported over 25.5 gigawatt-hours of electricity to the grid since becoming operational in 2017. The project sent a record-breaking 13.8 gigawatt-hours (GWh) of electricity to the grid in 2019, doubling its previous high of 7.4GWh in 2018.
Meanwhile, last year, tidal energy startup Verdant Power began installing a system to deliver clean power from tidal and river currents in a real-world application. The Roosevelt Island Tidal Energy (RITE) installation, as the project is called, involves a set of three half-scale underwater generators being installed in the East River tidal strait. The trio of 35-kilowatt turbines sits on a single triangular base called a TriFrame.
The turbines use a Free Flow System that generates clean electricity from the East River’s natural tidal currents. The energy generated would go straight into New York City’s power grid – a region hungry for renewable energy but possessing limited means to generate it locally.
Environmental Concerns
Some environmental concerns with tidal energy include blade strike and entanglement of marine organisms, as high-speed water boosts the risk of organisms being pulled near or through these devices.
Like offshore renewable energies, there is also a concern about how acoustic outputs and electromagnetic fields may affect marine organisms. Since these turbines are in the water, the acoustic output can be far greater than those created with offshore wind energy. This acoustic output can affect marine mammals, particularly those who echolocate to navigate and communicate, such as whales and dolphins.
