OSLO (Reuters) – Homes on the Arctic tip of Norway started getting power from the moon on Saturday via a unique subsea power station driven by the rise and fall of the tide.

A tidal current in a sea channel near the town of Hammerfest, caused by the gravitational tug of the moon on the earth, started turning the 33-foot blades of a turbine bolted to the seabed to generate electricity for the local grid.

The prototype looks like an underwater windmill and is expected to generate about 700,000 kilowatt hours of non-polluting energy a year, or enough to light and heat about 30 homes.

“This is the first time in the world that electricity from a tidal current has been fed into a power grid,” Harald Johansen, managing director of Hammerfest Stroem which has led the project, told Reuters.

The plant in the Kvalsund channel, which had cost about $11 million by Saturday’s launch, is a tiny contributor to help cut dependence on fossil fuels like oil and gas blamed for global warming.

The water flows at about 8 feet per second for about 12 hours when the tide is rising through the Kvalsund channel, pauses at high tide and then reverses direction. The blades on the turbine automatically turn to face the current.

If successful, the project could herald far wider use of predictable tides in green energy and generate millions of dollars in orders. Windmills, by contrast, are useless in calm weather and have to be built to withstand hurricane-force winds.

Artificial Lagoons

Tides have previously been tapped for power plants in France, Canada and Russia in barrages that trap water in artificial lagoons at high tide. When the tide goes out, gravity sucks the water through turbines to generate electricity.

But such barrages can disrupt the habitats of animals and plants in river estuaries and along the coasts.

Proponents of turbines turned by tidal currents say that they cause less impact — they are silent and invisible from the surface and fish, whales and seals can probably swim round them without the risk of being sliced up.

Drawbacks are that costs are high. Hammerfest Stroem has estimated that electricity will cost about 0.30-0.35 crowns a Kilowatt hour to generate, three times that of typical hydro-generated electricity in Norway.

And maintenance — with divers having to go down to the seabed — could be tricky. Other subsea experiments to generate power from tidal currents from Australia to Britain have not got to the stage of feeding power into the grid.

Norwegian oil group Statoil, Swiss-Swedish engineering group ABB and local Norwegian utilities are partners in the Hammerfest Stroem scheme. “We want to get experience from this and see that we can also be a producer of green electricity,” said Hanne Lekva at Statoil.

($1=7.223 Norwegian Crown)