Wave energy news items around the world are increasing as more nations attempt to harness the power of the oceans' restless motion.
With the much higher density of water compared to air the size of any harnessing system for wave over wind energy can be much smaller for an equivalent amount of power generation, making it much more efficient.
Wind itself is intermittent and less predictable in nature.
Image Courtesy of the Pelamis Website
Sure wave action is dependent on wind conditions over water masses. Their actual height can vary greatly. For any surface-based energy harvester as the base water level for waves will vary with the tide, mounting the harvester needs to adjust for this.
Some areas are more constant in wave motion than others - often in areas that have strong prevailing winds. In many areas these tend to be on the western shores of countries. Tidal height differences vary markedly throughout the world.
Importantly for harvesting wave energy the force of wave's motion is detectable and therefore usable even at quite some distance below the surface. Water being incompressible, tends to conduct the pressure impulse well.
A number of developments such as the Pelamis and the WETNZ projects rely on surface effects of wave motion. Others have begun to explore generators situated below the surface, as in the Carnegie projects in Australia.
Photo Courtesy of the Carnegie Wave Site
The major advantage of below surface generators is that they do not create surface eyesores. There may however pose possible navigational risks. Ideally this problem can be minimised by siting them at depths greater than the maximum a ship will draw. Once again tidal variations are an important consideration in this. The allowed depth needs to allow for the lowest low tide level.
The cost of transmitting power to a land station influences the charges required for employing this source. Undersea transmission is more efficient with direct current. Cables need to be able to withstand the saline and active sea life environment. Shipping and leisure craft need to know locations to avoid snagging lines with anchors, trawling nets and other equipment.
For the same reasons the marine environment also increases wear on harvesting equipment. Fouling of the machinery will occur, necessitating appropriate protection with harm to marine life, and regular cleaning.
There are a number of projects already underway around the world, including the three mentioned above.
The best method for harvesting waves is probably yet to be developed.
Being a renewable resource makes wave energy news of great interest in the long term as one in the mix of alternative energy sources.
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