Tidal Turbines: Power From the Moon
By Don Willmott
Sure, solar power is all well and good, but is there anything else up in the sky that might be able to serve as a free and abundant energy source? Maybe we should ask the Man in the Moon.
You don’t have to take a trip to the Bay of Fundy to realize that the rise and fall of the tides can be remarkably powerful, especially in locales where strong tides funnel through narrow passages sometimes referred to as “pinch points.” Carefully placed underwater turbines have the potential to spin water into wattage, and research and experimentation going on for more than a decade is beginning to yield some promising results.
In northern Scotland, for example, the Pentland Firth, which separates Scotland from the Orkney Islands, is an ideal location for tidal energy collection. Research suggests that it could ultimately meet up to 50 percent of Scotland’s total energy demand, with GE Power Conversion leading the way in turbine design and experimentation. The turbines, which look like airplane propellers, sit in 180 to 240 feet of water, and capture energy from both the horizontal and vertical tidal movements.
Another upcoming UK project, a billion-dollar man-made tidal lagoon with a 30-foot tidal range at Swansea Bay in Wales, will kick off construction in 2015. If its 26 giant turbines prove successful, four more projects are on the drawing board, which proponents say would provide up to 10 percent of Britain’s domestic electricity needs while also creating thousands of jobs.
In the United States, Verdant Power has spent more than a decade on its Roosevelt Island Tidal Energy (RITE) Project to prove the potential of tidal power in New York City’s East River. Sticklers may note that the East River isn’t a river at all. It’s actually a tidal strait that separates Manhattan from Long Island, and its impressive four-times-a-day tidal pull is well known to anyone who has ever watched a Brooklyn ferry try to poke its front end into a dock at full throttle while its back end swings away.
When the speed of the tidal flow exceeds two knots (about 3.3 feet per second), the five Kinetic Hydropower System turbines currently in place rotate at about 40 RPM and generate electricity for four hours. When the tide turns, so do the turbines, and their energy collection remains steady and predictable. So far there have been no concerns about environmental impact or marine navigation.
Verdant Power is authorized to install up to 30 turbines, and its ultimate goal is to have as many as 300 spinning away. How much energy will they actually generate? Not a lot, about 10 megawatts, or enough to power about 10,000 homes. But as a proof of concept, the project is already seen as a success.
And there will be more. Last year, the U.S. Department of Energy provided more than $16 million in funding for new tidal and wave energy projects, and it’s currently underwriting 17 demonstration projects, fueled by a pie-in-the-sky prediction that there are 1,400 terawatt hours of potential energy to be pulled out of the water annually, which would be enough to power 12 million homes… even on cloudy nights.
Don Willmott is a New York-based journalist who writes about technology, travel, and the environment for a wide variety of publications and websites.