2. Niederaussem, Cologne, Germany

The Niederaussem Unit K is a supercritical boiler with a boiler efficiency of almost 95% (LHV) with steam pressure of approximately 3,988 psig and steam temperatures of 1,076F. The plant electrical efficiency is over 43% (LHV). Alstom (Paris, France) was the consortium leader for the engineering, construction, and commissioning of the steam generator. The unit’s owner is RWE Rheinbraun AG (Essen, Germany).

Hammerfest, Norway, with 11,000 inhabitants, calls itself the world’s northernmost town. In December, tidal currents started turning the blades of a windmill-like turbine standing on the seabed near Kvalsund at the Arctic tip of the country. “We will be the first in the world to use tidal currents to generate electricity to be fed into the local grid,” said Harald Johansen, managing director of Hammerfest Stroem (Oslo, Norway).

Hammerfest Stroem uses proprietary water “wind mill” technology to convert the kinetic energy in a tidal current into electricity. In Kvalsund, the water flows at about 7.5 feet per second, apart from a pause at high and low tides. The 300-kW tidal stream turbine with 45- to 48-ft long blades is mounted on 200-ton towers placed on the seabed. The turbine automatically turns to face the tide when the currents change direction, and the propeller blades automatically adjust to their optimum orientation in the prevailing current (Figure 3).

3. Hammerfest Stroem, Norway

Johansen reckons the project has cost $6.7 million so far and will cost almost $15 million to complete installation of all 20 turbines by 2004. The production cost of the electricity is estimated to be 4.3 to 5 cents/kWh, three times that of typical hydro-generated electricity in Norway. Tidal power will be added to the mix of electricity in the local grid, and consumers will be required to absorb the cost.

The biggest tidal powerplant in the world is on the La Rance River in northern France and has been in place since the 1960s. It has a 240-MW capacity, but Electricité de France has no plans to build new ones. Canada’s Bay of Fundy in Nova Scotia has the highest tides in the world, at about 39 ft. Nova Scotia Power’s 20-MW plant at Annapolis Royal, built in 1984, is the only one in North America; the company is focusing more on wind.

Experts are uncertain about the potential of tidal power, especially because of sub-sea maintenance costs. Storms have wrecked many experimental ocean-power stations.

The British firm Marine Current Turbines, which plans to test a similar tidal current system off Devon in southern England next year, says that maintenance could be a problem for Hammerfest. “When you have strong enough currents for tidal-energy generation, there are few slack tides when divers can work,” said Peter Fraenkel, the group’s technical director.