AS the world looks to curb climate change and reduce fossil fuel emissions, some companies are focusing on a relatively untapped but vast and abundant source of energy: tidal waves. Off the coast of Scotland, Orbital Marine Power operates what it says is the “most powerful tidal turbine in the world.” The turbine is approximately the size of a passenger airplane and even looks similar, with its central platform floating on the water and two wings extending downwards on either side. At the ends of each wing, about 18 meters below the surface, are large rotors whose movement is dictated by the waves. “The energy itself of tidal streams is familiar to people, it’s kinetic energy, so it’s not too dissimilar to something like wind,” said Andrew Scott, Orbital’s CEO. “The bits of technology that generate power look not too different to a wind turbine.” But there are some key differences to wind energy, primarily that waves are far more predictable than winds. The ebb and flow of tides rarely differs significantly and can be timed far more precisely. “You can predict those motions years and decades in advance,” Scott said. “But also from a direction perspective, they only really come from two directions and they’re almost 180 degrees,” he added, unlike wind turbines that must account for wind from several different directions at once. Tidal waves are also capable of generating more energy than wind, Scott says. “Seawater is 800 times the density of wind,” he said. “So the flow speeds are far slower, but they generate far more energy.” The Orbital turbine, which is connected to the electricity grid in Scotland’s Orkney, can produce up to two megawatts — enough to power 2,000 homes a year. Scott acknowledges that some challenges remain including the high cost of the technology, but the reliability and potential of tidal energy could make it a useful tool in the fight against climate change. Around 4,828 kilometers away from Orbital’s turbines, Verdant Power is using similar technology to generate power near Roosevelt Island in New York City’s East River. Although not on the market yet, Verdant’s turbines set up as part of a pilot project help supply electricity to New York’s grid. But rather than float near the surface, they’re mounted on a frame that’s lowered to the bottom of the river. “The best way to envision Verdant Power’s technology is to think of wind turbines underwater,” said the company’s founder, Trey Taylor. And river currents tend to provide the same advantages for energy generation as ocean currents, he explained. “What’s nice about our rivers and systems is that could be 24/7 power,” he said. “Not to ding wind or solar, but the wind doesn’t always blow and the sun doesn’t always shine. But river currents, depending on the river, could be 24/7.” Over the course of eight months, Verdant has generated enough electricity to power roughly 60 homes, though Taylor says a full-fledged power plant built on its technology could generate enough for 6,000 homes. “The potential for energy is something like 250 gigawatts around the world,” he said, which is enough to power 250 million homes for a year. “There’s lots of room and we really hope our competitors succeed too, for the sake of the industry.” The biggest obstacle to reaching that goal at the moment is how expensive it is to set up and scale up tidal power systems. The U.S. Sandia National Laboratories estimates that tidal energy is two or three decades behind wind energy in terms of adoption and scale. The costs and challenges of operating underwater are something both Scott and Taylor acknowledge. (SD-Agencies) | 