Scotland doesn’t have much in the way of sunshine for solar power, but it does have a huge surging sea that is perfect for the energy source of the future – tidal power.
Scotland may seem an unlikely candidate to lead a renewable energy revolution. It doesn’t have much sun for solar power or giant coursing rivers for hydro. It does, however, have endless miles of beautiful coastline and a restless sea whose tides ebb and flow with tremendous force.
Energy companies in Scotland are seeing the potential of underwater turbines which tap a constant and predictable source of energy, are invisible, and can produce as much electricity as a conventional wind turbine.
In Scotland, a project in the fast-flowing marine waters of Pentland Firth in the far north of the country last year hit a milestone. Its array of four submerged turbines generated enough energy from the powerful tides to power nearly 4,000 homes in 2019.
The four giant turbines have now exported 24.7-gigawatt-hours (GWh) of predictable renewable power to the national grid.
And this is just the first phase of a project that could eventually power 175,000 homes with more than 250 submerged turbines.
The array is off the mainland of Scotland, near the uninhabited island of Stroma in a natural channel that speeds up the tidal flow of water between the North Sea and the Atlantic Ocean.
Seawater is 832 times denser than air, which means the turbines can be smaller while producing a similar amount of energy to a wind turbine.
The force of these tides also means the turbines can be placed closer together, taking up less space on the sea bed than an equivalent wind farm on land.
Apart from being invisible – obviating a factor that has stalled many wind farm projects on land — marine turbines have the great advantage of tapping an energy source that does not rely on the weather.
Other renewables such as wind, wave, solar and even hydroelectricity depend in large part on seasonal and climatic features. Tidal turbines, meanwhile, get two regular tide changes a day.
“We can forecast over the next 100 years pretty accurately — we know when the power’s coming,” a spokesman for MeyGen said.
The turbines, which were submerged in 2014, are lined up 525 feet (160 m) apart and weighted to the sea bed with scrap metal.
With a depth of 130 ft (40 m), the company says that vessels would have a clearance of about eight metres, plenty, he says, for the small craft that ply the four-mile region.
“These are really cut down versions of wind turbines, such that most of the electrical equipment is onshore so that if something goes wrong, we can get a Land Rover and drive to the substation rather than having to get a boat and pick them up,” the spokesman said.
“That’s one of the core advantages of this technology.”
Concerns over the impact on marine life were also raised during the planning process, but the simple fact is the turbines move so slowly – at between 12-18 RPM – that experts believe most sea life have been able to either ignore or get out of the way of the blades with ease.
He said undersea monitors have been logging the wildlife in the region over the past five years and that various groups now have a clear baseline of which animals populate it.
“There has been a lot of work done in other parts of the world on how seals and whales interact with these turbines and they do actually get a bit curious,” the spokesman said.
“But these rotations of the blades are quite slow in comparison with wind turbines and the theory is that they can just get out of the way.”
He said research had shown that most marine life avoids tidal surges when they are in full flow.
“I can imagine seals dancing around them, but the only time they’ll be playing around them is when the flow is benign — and that only lasts for about an hour and a half and at that time the blades aren’t rotating.
“We don’t want to be blasé about it, but at the same time we have a high degree of confidence.”
The immediate future of the energy source is looking good, with leases around Scotland showing the potential to produce 1.2GW. That’s more than twice the energy produced by an average-sized nuclear power plant.