Breezes can be too weak or too strong for windmills to work properly and in places like the north of Norway the sun completely disappears for several months each year, rendering solar power inefficient in winter. The tides, however, are as sure as the moon.
Tidal turbines are also hidden beneath the surface of the water and thus do not blight the visual horizon. Windmills have been criticized as an eyesore by several community and environmental groups.
The tips of the blades are 66 feet (20 meters) below the water's surface, allowing clear passage for ships and slowly rotate led by their rounded edge, thus posing little threat to fish and other sea critters, according to Bekken.
The one adverse impact recognized by proponents of the technology is to the fishing industry, as fishing equipment could get tangled up in the turbines. As a result, fishing must be restricted in turbine locations.
Since the 1960s, energy producers have reaped electricity from the tides by trapping the high tide in artificial lagoons with dams. When the tide goes out, gravity sucks the water through turbines to generate electricity, much like a hydroelectric system on a river.
Environmentalists and fisheries groups, however, said the projectsthe largest of which is in la Rance, Francedamage habitat and alter water circulation patterns as far out as 300 miles (500 kilometers) from the power plant.
The tidal turbines, by contrast, do not require a dam. The structures are simply plunked into the water and bolted to the seafloor.
"This one may have the ability to harvest enough energy to make it worthwhile and not interfere with circulatory patterns, but it will probably be a site-specific equation," said Charter.
The tidal turbine technology is only just now being attempted because it has taken several decades for the wind industry to perfect the windmill, a design the tidal turbine engineers borrow heavily from, said Bekken.
"Also, advances in sub-sea technology have been brought up to the level where we can use it for this kind of project as well," he said.
For example, Charter said that advances in materials science in the last decade have allowed engineers to design equipment that can withstand the corrosive effects of salt water.
Once the technology is scaled up, Bekken hopes the costs of tidal turbines to be comparable with windmills. The development cost of the prototype is about U.S. $11 million to date.
In order to keep maintenance costs down, duplicates of all important systems are built into the turbine so that if one breaks the other can be switched on instead of having to dispatch a scuba diver to fix it.
The project's backers, which in addition to Hammerfest Strøm include the Norwegian oil group Statoil, the international engineering group ABB, Norwegian arm of Rolls Royce, and local Norwegian utilities, hope to sell thousands of the units to help Europe meet its green energy requirements.
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