Tidal Turbines
Tidal turbines are best described as underwater wind mills, but with shorter blades rotating at slower speed. Designed for water depths of between 35 and 100 m, the tidal turbines are deployed on the seabed and kept in position by gravity, pins or pilings (depending on the seabed and tidal stream characteristics). This eliminates any visual or audible impact above the surface and, in addition, normal shipping traffic will not be affected by the presence of the tidal arrays. The whole substructure is designed to have a small footprint while the nacelle is optimize to minimize the wake effect caused by the water flows. Unique marine installati
on methodologies have been developed to minimize installation times and to exclude the use of divers, requiring only the support of Remotely Operated Vehicles (ROV) for monitoring purposes.
Main parts of the turbine
- Nacelle
- Hub
- Blades
- Yaw
- Substructure
Technical characteristics
- Rated power: 500-2,000 kW (site dependant)
- Power regulation: Variable pitch, yawing system, variable speed
- Operating depth: 35-100 m
Rotor
- Type: 3 bladed open
- Rotor swept area: 300-500 m²
- Nominal speed: approx. 10 rpm
Generator
- Type: Induction
- Nominal output: 500-2,000 kW
Weight
- Nacelle: approx. 130 t
- Substructure: approx. 150 t
- Installation: Heavy lift vessel/barge (with ROV support)
- Lifetime/Service: 25 years/every 5 years
Tidal forces are a result of periodic variations in the gravitational attraction exerted by both the sun and moon together with the centrifugal forces associated with the rotation of the earth.
Tidal characteristics are mainly influenced by bathymetric conditions, coastline morphology and current directions. In some specific regions, high tidal ranges can result in strong currents, which are the basis for the ANDRITZ HYDRO Hammerfest technology, allowing highly predictable and reliable energy generation.
The forces produced by the tides can be basically used to generate electricity in two different ways:
Potential energy
Energy from a water head is called potential energy. By using pressure turbines, this energy can be converted into electrical power.
Typical examples are tidal barrages, which make use of the potential energy available from the difference in head between high and low tides.
Kinetic energy
The kinetic energy of moving water can be converted into electrical power by using tidal turbines. This form of energy yield is the basis of our technology.
The turbines are placed in areas with high tidal movements, and are designed to capture the kinetic motion of the ebbing and surging of ocean tides producing strong bidirectional currents that can be converted into electrical power. Unlike barrage-type systems, this technology does not require the construction of a barrier across a waterway, and hence does not have any of the adverse environmental effects associated with such developments.