Saltwater is brutal on anything mechanical. Park a boat trailer near the coast and the bolts seize within a season. Drop a steel structure into a tidal channel and corrosion, marine growth, and the constant battering of the current usually find a way in within a few years. So the idea of bolting a spinning generator to the seabed 100 feet down, in some of the fastest tides on the planet, and leaving it there sounds like a maintenance invoice waiting to happen.<\/p>\n
Off the northern tip of Scotland, four of them have been feeding the grid since 2018. And as of late last year, one of those turbines had run seven years straight without anyone needing to touch it.<\/p>\n
The site is called MeyGen, and it sits in the Inner Sound of the Pentland Firth, the narrow channel between the Scottish mainland and the uninhabited island of Stroma. It is, by most accounts, the largest tidal stream array in the world. Four turbines, 1.5 megawatts each, dropped onto the seabed in a stretch of water where millions of tons move between the North Sea and the Atlantic every single day. The reason it matters has nothing to do with looking impressive on a press release and everything to do with that maintenance record, because reliability is the exact thing tidal power has been failing at for two decades.<\/p>\n
Most things you build at sea get hammered into the seabed. Offshore wind turbines sit on monopiles driven deep into the ground, which works fine until you try it in a tidal race moving at 10 knots, where the seabed is hard rock and the current would make precision pile driving a nightmare. MeyGen skips all of it. Each turbine, per project owner Ampeak Energy<\/a>, sits on a 1,450-ton gravity foundation that holds the whole thing down with nothing but its own weight. No piles, no drilling for the base. The turbine itself weighs about 150 tons and clamps onto that concrete sled, and the combined mass is enough to stay put in flows that hit 10 knots, close to 12 miles per hour of moving water.<\/p>\n The turbines are three-bladed, with rotors about 18 meters across, roughly 59 feet tip to tip. The blades pitch to manage load once the current passes the speed where they hit full output, and a yaw module swings the whole machine around at each slack tide so it faces into the next flood or ebb. Power runs ashore through a quad-armored subsea cable laid right on the seabed, then up through a borehole drilled horizontally into the bedrock at the shoreline.<\/p>\n Onshore, the 4-kilovolt supply gets stepped up through an ABB converter to 33 kilovolts to meet grid code before it enters the local network. It is clever engineering, and the best compliment you can pay it is that for seven years it mostly just sat there and worked.<\/p>\n Here is the part that made the rounds. In December 2025, Ampeak and its turbine partner Proteus Marine Renewables finished a round of offshore work on three of the four turbines. Two of them, TTG 2 and TTG 4, were serviced offshore and dropped back into operation. A third, TTG 1, got sent back to the Nigg yard for servicing and will be redeployed later. The fourth, TTG 3, needed nothing. According to the announcement covered by Eco Magazine<\/a>, it had by then accumulated seven years of operation, maintenance-free.<\/p>\n That is the number tidal has been chasing forever. Earlier, in mid-2025, bearing and seal supplier SKF had flagged the same array passing six years without unplanned or disruptive maintenance and called it a world record for tidal turbine reliability. The December work pushed it further, and Proteus tacked on a second claim: five turbine interventions in three days without the vessel leaving the site, servicing two units on deck and returning them subsea.<\/p>\n Drew Blaxland, the Proteus CEO, described that operation as “another world record” and argued it proves the commercial case for seabed-mounted turbines. Whether or not you want to count the records, the underlying point holds. They put machines in the worst possible environment, left them for the better part of a decade, and the things kept generating.<\/p>\n Tidal power has always had one enormous advantage and one enormous problem. The advantage is predictability. Unlike wind or solar, the tide runs on the moon, so you know exactly when the current will flow and how hard, years in advance. The problem is that the ocean destroys hardware. Keeping a turbine spinning underwater in a corrosive, high-flow environment for any real length of time has been the technical wall the whole sector kept hitting, because when a key component fails 100 feet down, fixing it means a vessel, a weather window, and a very large bill.<\/p>\n That is why the MeyGen record is worth more than the megawatts it has produced. The site runs a condition-based maintenance approach, which means you service the machine when the sensors say it needs it rather than on a fixed schedule, and the design targets years between major overhauls. MeyGen has now delivered more than 84 gigawatt-hours of electricity since 2018, enough to account for over 90 percent of the United Kingdom’s entire tidal stream output, and it has done it while proving the hardware can survive.<\/p>\n For a sector trying to convince investors and governments it deserves a seat next to wind and solar, that survivability is the whole pitch. It is the same reliability question that hangs over every big renewable machine, from China’s record-breaking offshore wind turbines<\/a> to the river and hybrid installations Germany is building along the Rhine<\/a>. The tide just happens to be the harshest place to ask it.<\/p>\n What is in the water now is technically the pilot. Phase 1 is the four turbines, 6 megawatts total, which hit full output for the first time in late 2024 once the last of the four was deployed. The array reaches around 6,000 homes’ worth of power, and more importantly, it has handed the operator nearly a decade of real operating data to take into the next round.<\/p>\n That next round is where it gets commercial. MeyGen has secured Contracts for Difference, the UK’s guaranteed-price support mechanism, across three allocation rounds for a combined 59 megawatts, with target commissioning dates running from 2027 through 2029. The first 28-megawatt tranche, awarded back in 2022 at a guaranteed \u00a3178.54 per megawatt-hour, is aimed at 2027. Bigger turbines are part of the plan, with Proteus moving toward 3-megawatt machines for the expansion.<\/p>\n And the ceiling is much higher than 59 megawatts. The original Crown Estate lease for the Inner Sound site covers up to 398 megawatts of installed capacity, which is the number the project keeps pointing at for the long-term build-out. Getting there depends on grid upgrades and a lot more financing, so it is a target rather than a timeline. But the lease is real, and so is the proof that the hardware lasts.<\/p>\nSeven years down, and one turbine never had to come up<\/h2>\n
Saltwater is why nobody had pulled this off before<\/h2>\n
A 6-megawatt pilot with a 398-megawatt lease behind it<\/h2>\n
The same machines are now pointed at Alaska<\/h2>\n