TWISTER Norwegian device will be first to be hooked up to a grid. (Photo courtesy of Allan Klo/Finnimark Dagblad)

It’s a busy time for a new generation of underwater devices capturing energy from flowing tidal currents. The first machine to be hooked up to a grid is due to begin generating electricity any day now inside Norway’s Arctic Circle, while two experimental units are under operational evaluation in the U.K. One developer believes commercial exploitation could be just four years away.

After a year’s delay, Norwegian engineers last month installed a 300-kw windmill-like turbine in Kval Sound, south of Hammerfest, one of the world’s northernmost towns. Longer-than-expected precommissioning work and associated funding strains cost the developer its lead over the U.K., says Bjorn Bekken, project manager at Hammerfest Strøm A.S., Hammerfest.

A year’s trials lie ahead for the turbine, says Bekken. With the bulk of its roughly $3-million cost stemming from the development, a 20-unit farm already seems realistic, he suggests. "We have a [cost] target which should match wind power," he says. The device will feed electricity to Hammerfest municipality, the lead shareholder in the development, which also includes Statoil A.S., Oslo, and Switzerland-based ABB Group.

Immersed in 50 m of water, the generator taps tidal currents in the 600-m-wide sound to turn three 10-m-long fiber-reinforced composite blades. Blades can rotate about their axis to function with reversing flows. Generating equipment is housed in a 10-m-long nacelle, weighing 54 tonnes, atop a three-legged tube-steel frame. The substructure’s 320 tonnes include 200 tonnes of weights anchoring its feet to the bed.

In design, the Hammerf-est machine’s nearest U.K. rival was installed in the Severn Estuary this May (ENR 7/1/02 p. 17). Also rated at 300 kw, it has a turbine mounted on a single vertical tube founded in the bed. Including U.K. and German components, it arose as part of the $5.8-million Seaflow project. After a year’s trials, the next step could be a twin turbine unit, also on a single support.