Muddy seafloors extract energy from ocean waves, decreasing wave height and lessening intensity. In the Gulf of Mexico, this interaction is so strong that it creates what is locally referred to as the “mud hole,” a 100-200 meter spot on the water for fishermen to safely wait out storms.

One engineer has proposed a new energy-harvesting technique that would mimic this interaction. In a recent article published in The Royal Society journal, Mohammad-Reza Alam, an engineer with the University of California, Berkeley, theorizes that energy could be harvested through a viscoelastic “carpet” consisting of springs and generators on the seabed. The system mimics mud, rippling underneath passing waves and absorbing energy. If employed, this technology would both harvest energy and create safer coastlines by decreasing wave intensity.

In a model of the proposed carpet, Alam showed the system could absorb half of incident wave energy over short distances, resulting in energy absorption rates up to 6.5 kW m–2, which is higher than both wind turbines and solar-power converters. The model also showed that short waves are dampened faster than swells, making areas with choppy waters ideal for harvesting energy on the seafloor.

Alam’s seabed carpet has a few advantages over other wave energy-harvesting systems. It performs well in storms, because the choppy waters provide more energy. Other systems use floating devices or clam-like structures that cannot function properly in adverse weather. The carpet can also harvest energy no matter the direction of the wave. In addition, the flat design would not post threats to marine mammals or passing ships.

Limitations of the carpet, however, would restrict its use in a great number of areas. The carpet is most efficient within about 20 meters of the ocean surface, restricting placement away from coastlines. In addition, moving sediment could cover parts of the device and make it less effective, so Alam suggests it may be best used along rocky coastlines.

Photo credit: Malene Thyssen