A spinning turbine making electricity under 44 yards of water off the coast of Scotland just passed the 6.5-year mark without needing any repairs. It’s a big deal, advocates say. The feat boosts the turbine's status as a commercially successful way to produce clean energy. The achievement is a “very (big) milestone” for a blooming form of sustainable energy, Rémi Gruet told The Associated Press (AP). He's the CEO of Ocean Energy Europe. What's the reason? The turbine’s durability shows that underwater turbines can be cost-effective if they don't need repairs often. There are only a handful of these projects around the world. But tidal energy is better in some ways than wind and solar power. The density of water is hundreds of times greater than air. So turbines below water can produce a great deal of power even at low speeds. They rotate with the rise and retreat of the tides. And they rely on the gravitational forces produced by the sun and moon. This means the energy source can't be exhausted. Plus, it's predictable. Tidal patterns can be forecast years in advance. The turbine, which was installed by a company called MeyGen, is one of four located in a narrow channel between Stroma Island and the northern coast of Scotland. Combined, they produce 1.5 megawatts each. That's enough to provide power for as many as 7,000 homes. The four turbines currently represent the largest tidal energy project on the planet. “It’s a title we wish we didn’t have,” MeyGen operations and maintenance manager Fraser Johnson told the AP. “We want more, we want others.” MeyGen and its Swedish partner, SKF, plan to add 20 turbines to the site in 2030. Eventually, they would like to reach a total of 130. Reflect: What are some ways you think new technologies can change the way we use energy in our daily lives? Gif of the ocean from GIPHY.