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Off Grid Energy Independence
Posted on June 22, 2012 by  & 

Wave carpet to harvest ocean energy

Knowledges Based Systems Inc's (KBSI) Wave Carpet initiative, funded by the Office of Naval Research, has designed a deep-water, offshore, wave-powered floating system that absorbs the energy of wind-generated water waves.
In order to design wave energy devices, it is essential to understand the nature of water waves and the operation of wave energy devices at sea. This initiative focused on the main issues and problems facing wave energy absorption, integrating knowledge in the fields of wave hydrodynamics, distributed controls, wave to electric power generation and artificial intelligence algorithms.
The feature of the Wave Carpet design that distinguishes it from current wave energy systems is its ability to be rapidly redeployed using self-propulsion as required in Navy applications. The main technology components in this innovative design are large, flexible, floating body hydrodynamics, distributed controls and an embedded fault redundant electric power grid that supports energy storage and is augmented by fluid power storage. The system is dynamically positioned using its own power.
Both the redeployability and inherent power fluctuation smoothing are key features of the Wave Carpet design. The wave carpet can be redeployed using a remote control, thus limiting risks to divers during combat operations or, simply, during bad weather. In addition, the Wave Carpet provides energy storage without the need for connecting to an existing grid: a significant advancement over existing wave power designs. The Wave Carpet absorbs the cost of evening out power fluctuations into its own structure, and is designed to minimize the total cost of ownership including deployment and maintenance costs.
The Wave Carpet technology also holds the possibility of developing very large floating smart structures in the ocean, which could be used as wave dampers for controlling sea states or wave loading for protecting structures like ocean thermal energy conversion structures or other large offshore structures. This technology could also be used as floating breakwaters for sea farming. Energy could be harvested as a byproduct, creating a relatively steady ocean power source. Eventually, the Wave Carpet technology could also provide propulsion with reduced acoustic noise: an ability that is critical in stealth applications. The Carpet surface can also be redesigned to be part of rapidly reconfigurable hull designs.
Researcher Mohammad-Reza Alam at the University of California, Berkeley also recently reported that it is known that muddy seafloors can extract significant energy from overpassing surface waves via engaging them in strong interaction processes. If a synthetic seabed can respond to the action of surface gravity waves similar to the mud response, then it too can take out a lot of energy from surface waves.
Alam and his group focussed their attention on an artificial viscoelastic seabed carpet composed of (vertically acting) linear springs and generators to show that the system of sea/synthetic-carpet admits two propagating wave solutions: the surface mode and the bottom mode. The damping of a surface-mode wave is proportional to its wavelength and hence is classic. However, the damping of a bottom-mode wave is larger for shorter waves, and is in general stronger than that of the surface-mode wave.
Sources: Knowledge Based Systems Inc (KSBI) and The Royal Society
Top image: Nature Kaku
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