ability to produce power. (See related pictures: "Nature Yields New Ideas for Energy and Efficiency.")
Anchored 1.25 to 6.2 miles (2 to 10 kilometers) from shore, the Pelamis can naturally spin on a chain to face wave direction like a flag changes orientation on a flagpole. Five floating tube sections are linked by universal joints that flex in two different directions as waves roll down the machine's serpentine length. Each joint houses cylinders that resist the wave-driven movements and pump hydraulic fluid to power onboard generators, sending electricity to shore via underwater cables. The Pelamis can handle dangerous storm swells much like a surfer paddling out to a favorite break: When big waves roll in, it simply passes through and under them.
Pelamis has produced six full-scale machines so far, each rated at 750 kW. Over the past 15 years they have logged more than 10,000 hours at sea while connected to real electrical grids, notably at the European Marine Energy Centre (EMEC), off the west coast of the Orkney mainland.
The company plans to debut its technology commercially with Farr Point Wave Farm, a ten-machine project off the Sutherland coast that is set to produce power by 2017. Pelamis has several other plans currently on the drawing board.
The UK energy supplier E. ON and ScottishPower Renewables each own a Pelamis machine currently in sea testing at the EMEC. Each company has ambitions to develop a wave farm, E.ON's in waters north of EMEC and Scottish Power Renewables' off Marwick Head in Orkney. These operations could link as many as 66 machines each and produce 50MW of power at each location. Pelamis has also partnered with Vattenfall to develop a 10MW wave farm, using up to 14 machines, off the Shetland Islands and is planning another 10MW facility off the west coast of Lewis in the Outer Hebrides. And in Aguçadoura, Portugal, past site of a three-machine Pelamis farm, Companhia da Energia Oceânica SA (CEO) might install as many as 26 machines with a target capacity of 20MW.
Pelamis is one of five competitors vying for the £10 million ($16.6 million) Saltire Prize, offered by the government of Scotland to the first company able to create a viable green energy system that taps the energy constantly churning offshore. (Terry Garcia, National Geographic executive vice president for mission programs, chairs the Saltire Prize committee.) Scotland has some of the world's most promising wave and tidal energy resources and has led the way in promoting their development. (Related: Ocean Energy Teams Compete for $16 Million Scotland Prize.)
Seafloor "Magic Carpet" For Power, Desalination, and Coastal Protection
Reza Alam, a UC Berkeley engineer and expert at wave mechanics, has created a power-producing "magic carpet" that serves as an artificial ocean bottom with multiple applications.
"Mud is known to very strongly dampen ocean waves. Within a distance of a couple of hundred yards even very strong waves can be completely dampened out," he said. "So we were inspired to wonder if a synthetic carpet could respond similarly to the action of waves and absorb that same amount of energy."
The device features a thin rubber or elastic composite carpet stretched across across a grid of cylinders and double-action piston pumps. The carpet adopts the up and down wave motion of its waters and subsequently moves the attached piston pumps to produce hydraulic pressure with multiple applications.
"The first idea was desalination, near the device or onshore, because high-pressure water is something we need for that," Alam explained. The system can also be customized to deliver compressed air, rather than water, for offshore aquaculture, where it could be used to move cages and oxygenate water.
And of course the system could generate electricity—perhaps in surprising quantities. In recent wave tank tests, it absorbed more than 90 percent of incoming wave energy. With that kind of results, Alam estimated, a single square meter (11 square feet) of carpet system on a seafloor could power a pair of U.S. homes. A 100-square-meter (1