ENERGY

A Scottish tidal power plant has broken a record, the owner announces. It has produced 50 GWh of electricity during its lifetime.

The power plant on the north coast of Scotland is called Meygen and has been installed by SAE Renewables. The facility began providing electricity in commercial operation in 2018.

The turbines sit 20 meters below the surface of the water in the Pentland Strait, between the Scottish mainland and the Orkney Islands.

“This unseen and sometimes forgotten place has some of the strongest tidal currents in the world and is a predictable source of renewable electricity,” writes Graham Reid, CEO of SAE Renewables in a blog post.

A yaw module allows the turbines to rotate

According to the company, since the power plant was put into operation, it has produced 50 GWh of electricity. That is more than twice as much as all other tidal power plants worldwide have produced combined, writes Graham Reid.

It is also more than what an average land-based wind turbine produces in five years, i.e. 30 GWh of electricity. But the comparison is somewhat lame because the wind farm only has one turbine, while the Meygen tidal power plant includes four turbines.

Construction of Meygen started in 2015. The four turbines of 1.5 MW each have been mounted on gravity foundations. Each turbine has three blades and a rotor diameter of 18 meters.

Like wind turbines, the rotor blades can be rotated in relation to the hub. The tidal turbines are also equipped with a yaw module that rotates the turbine each time the tide turns between ebb and flow.

The facilities are expensive to build

SAE Renewables expects the tidal power plant to provide enough electricity to power about 6,000 households each year.

The company is now planning an expansion in several stages. It is hoped that the power plant will eventually reach a capacity of 312 MW.

Even further north, in the Shetland Islands, another tidal power company recently broke a world record for the most number of turbines. The company Nova Innovations operates The Shetland Tidal Array, which now has six turbines.

The difficulty in developing tidal power plants is the harsh marine environment. The equipment must stand up against corrosion and be able to cope without maintenance for long periods of time. This makes the facilities expensive to build.

New rotor blades must be tested

At the beginning of the year, a new EU project started, Max blades, with the hope of bringing the cost down. Both companies and universities are part of the project and the aim is to evaluate an increase in the length of the rotor blades from 10 to 13 metres. That would provide a sweeping surface that is 70 percent larger for the rotor.

The new blades will first be evaluated in a test facility at the University of Edinburgh and then installed in the waters off the Orkney Islands.

The theoretical potential to extract power from tidal energy is ranked at 1,200 TWh per year by Irena, the International Renewable Energy Agency, in a report from 2020. It is less than the potential to produce electricity from the sun, wind or waves, but the tide has the advantage of not being affected by the weather and moving in a predictable pattern.

Precisely the predictability makes it suitable to combine tidal power with more uneven renewable energy sources such as solar and wind power. With such a combination, the entire British island of Isle of Wight could phase out its use of fossil-based electricity, researchers from the University of Plymouth recently concluded in a study.