After years of costly failures, is tidal energy finally catching on?

An array of underwater turbines that turn tidal energy into electricity hit an important early milestone off the coast of northern Scotland, the project’s developer said this week. The announcement strikes the rare bright note for a sector that’s struggled to gain a foothold despite decades of development and billions in investments.

On Monday, in the early morning hours, the MeyGen project became the first tidal stream array in the world to generate 50 gigawatt-hours of electricity over its lifespan, according to SAE Renewables, the Edinburgh-based developer. The company said that the total global generation from all other tidal devices and sites is less than half of that amount.

“Tidal can and does work, we just need to get more turbines in the water,” Graham Reid, CEO of SAE Renewables, said in a statement.

The MeyGen array, which began operating in 2017, includes four 1.5-megawatt turbines that sit some 66 feet below the water’s surface off the coast of the Pentland Firth. The strait separates the Orkney Islands from mainland Scotland, and it has some of the strongest tidal currents in the world.

“We have overcome many challenges, with reliability being an issue in the early days, but we have learned an immense amount along the way,” Reid continued.

By way of comparison, the 50 gigawatt-hours that MeyGen generated is roughly equal to the average annual electricity consumption of 4,700 U.S. households.

Ocean tides and waves — powerful, predictable and perpetually replenished — have long held immense allure for clean energy developers. Tidal stream technologies are concentrated in narrow bodies of water and are a subset of the larger marine energy sector, which also employs oceanic turbines, cylinders, dams and other subsurface contraptions. All told, tidal streams have the theoretical potential to generate 1,200 terawatt-hours of electricity per year, according to the International Renewable Energy Agency.

Yet installing and operating energy projects in the water remains logistically and technically complex. Harsh marine conditions, including salt water and repeated, powerful blows from the ocean, can erode or otherwise compromise components. Over the years, efforts to commercialize ocean energy technologies have resulted in several costly failures, including in 2009, when a Scottish company had to pull its $12.9 million ​“sea-snake” contraption out of the water almost immediately after installing the device.

Of the 30.2 megawatts of tidal stream projects installed in Europe since 2010, less than half that amount — or 11.5 megawatts — was still in the water as of 2021, the trade association Ocean Energy Europe said in a March 2022 report.

Still, developers worldwide say they’re committed to making these technologies work. Swedish startup Eco Wave Power has developed a way to generate electricity by installing equipment on breakwaters and seawalls. In January, the company announced that it had moved its ​“on-shore wave energy” technology from Gibraltar to the coast of California, where it plans to install the device at the Port of Los Angeles.

Other tidal-energy ventures include the Shetland Tidal Array, which has been powering Scotland’s grid since its installation in 2016, and Scottish engineering company Orbital Marine Power, which claims to have built the most powerful tidal turbine in the world. The Scottish government has helped fund these projects and the MeyGen array in an effort to boost the country’s renewable energy capacity while developing a homegrown industry.

“We will keep going,” Reid said in the statement. ​“Our MeyGen project will continue to break records and lead the industry.”