for National Geographic News
Energy derived from the moon now trickles into a village near the Arctic tip of Norway via a novel underwater windmill-like device powered by the rhythmic slosh of the tides.
The so-called tidal turbine is bolted to the floor of the Kvalsund Channel and was connected to the nearby town of Hammerfest's power grid on September 20. It is the first time in the world that electricity directly from a tidal current has been fed into a power grid.
The gravitational tug of the moon produces a swift tidal current there that courses through the channel at about 8 feet (2.5 meters) per second and spins the 33-foot-(10-meter) long blades of the turbine.
The blades automatically turn to face the ebb and flow of the tide and rotate at a pace of seven revolutions per minute, which is sufficient to produce 700,000 kilowatt hours of non-polluting energy per yearenough to power about 35 Norwegian homes (70 U.S. homes).
"Basically it's like putting a windmill in the water," said Bjørn Bekken, a project manager for Hammerfest Strøm, the company that built the device.
Richard Charter, a marine conservation advocate with Environmental Defense in Oakland, California, said the system has the potential to be a significant contributor to the natural energy mix, but warrants careful development.
"The good news is there are no carbon emissions, no radioactive plume or nuclear waste, no oil spill trajectory, and no chemical pollution," he said. "The thing is estuarine ecosystems are very sensitive."
The technology is so new, said Charter, that its impacts on things such as fish migration and water circulation patterns are not well understood. Environmental Defense is concerned the technology will be widely implemented too quickly.
"As an organization, we are generally supportive of a careful, methodical look at this technology," said Charter, "but it is too soon to make a call as to if it is the Promised Land of renewable energy."
Proponents of the tidal turbine technology say it is a welcome, environmentally friendly alternative-energy option. One key advantage over wind and solar power is that the energy output is 100 percent predictable, said Bekken.
"The tidal stream is going to be there and it is going to be exactly the same, you can predict it at all times," he said.
SOURCES AND RELATED WEB SITES