Cook Strait - Tidal Power

Tidal Power

In April 2008, a resource consent was granted to Neptune Power for the installation of a $10 million experimental underwater tidal stream turbine capable of producing one megawatt. The turbine has been designed in Britain, and will be built in New Zealand. It will be 14 metres in diameter and constructed of carbon fibre. It will be placed in eighty metres of water, 4.5 kilometres due south of Sinclair Head, in waters known as the “Karori rip”. Power from the turbine will be brought ashore at Vector's Island Bay substation. The turbine is a pilot, and will be sited in slower tides for testing. Neptune hopes to generate power from the unit by 2010. The company claims there is enough tidal movement in Cook Strait to generate 12 GW of power, more than one-and-a-half times New Zealand's current requirements. In practice, only some of this energy could be harnessed. As of April 2012 the Neptune Power website is a placeholder with no further announcements.

On the other side of the strait, Energy Pacifica has applied for resource consent to install up to 10 marine turbines, each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory Channel. They claim Tory Channel is an optimal site with a tidal current speed of 3.6 metres a second and the best combination of bathymetry and accessibility to the electricity network.

The power generated by tidal marine turbines varies as the cube of the tidal speed. Because the tidal speed doubles, eight times more tidal power is produced during spring tides than at neaps.