How it works

The tide differences are caused by the gravitation from the sun and the moon and the centrifugal powers on the turning earth. These powers cause a rise of the sea level both on the part of the earth that is facing towards and against the moon. That results in a change between a high tide and a low tide in a period of 12 hours and 25 minutes. A companionship between the sun and the moon causes a change between maximum and minimum tide difference in a period of 14 days. Bathymetric conditions also have an impact on the tide differences. The velocity of tidal currents varies by several factors.

The tide can be used to produce electricity in two ways:

	Potential energy: The energy from the head of water is called potential energy. By using low pressure turbines this energy can be converted into electrical energy.
	Kinetic energy: The kinetic energy can be converted into electrical energy by using tidal turbines.

ANDRITZ HYDRO Hammerfest exploits the kinetic energy in tidal water.

The tidal turbine is best describes as an underwater wind turbine, but with shorter blades that rotate slower. Each turbine will have an installed effect in excess of 1MW, and arrays may consist of hundreds of turbines. The tidal power devices are installed at 40-100 meters depth in tidal streams with velocity in excess of 2.5m/s. The turbines are installed on the seabed, and are not creating any visible or audible pollution above the surface and allows vessels to operate without restrictions. The energy is converted in both current directions by pitching the blades. The structure is designed as a tripod, which gives a minimal footprint on the seabed and is held in place by gravity and additional ballast.