Carpet is usually something you try not to get wet. Dirt is a rug’s worst enemy, and when you add moisture of any kind, it becomes a permanent stain faster than you can say “my name is Mud.” According to a study published recently in the Proceedings of the Royal Society, however, installing a special type of carpet on the ocean floor could be key to harvesting the energy of waves on the surface.
In order to understand the rationale behind this underwater carpet, you’ve got to know a little bit about how waves work. Ocean waves form when wind blows across the surface of the ocean. Waves can travel thousands of miles before reaching land, and range in size from small ripples to huge waves over 30 meters high. But it’s when the waves start to approach the shoreline that things get interesting.
As a wave gets closer to shore, it begins to drag on the muddy seafloor. This drag slows the wave down and usually shrinks its size (which is good news for those of us swimming near shore!) Watching the mud exert this force on powerful waves gave Mohammad-Reza Alam of the University of California, Berkeley, a brilliant idea: why not create a rug-like device that could absorb the wave’s energy as it passes overhead?
Alam calls his invention a viscoelastic “carpet of wave-energy conversion” (CWEC), and imagines placing it over a network of vertically oriented springs and generators on the coastal seafloor. “The gravitational force of waves overhead would make the carpet ripple, just as it interacts with mud on the sea floor, and that movement would be transferred to generators,” writes Tina Casey for Cleantechnica.
In early tests, Alam was able to show that the system can easily absorb 50 percent of incident wave energy over short distances of about 10 m. According to Physics World, that’s more than double the maximum possible with wind turbines and at least 20 times greater than currently achieved by solar-power convertors.
Unlike offshore wind turbines or other wave energy harvesting devices, the seabed carpet would be completely impervious to stormy weather. In fact, turbulent seas might actually increase power production.