Crest Energy Limited has been granted consents to construct a marine tidal turbine power station in the mouth of the Kaipara Harbour in Northland, northern New Zealand. The project comprises up to 200 completely submerged marine tidal turbines with a maximum generating capacity of around 200MW, located invisibly underwater.

Crest Energy estimates its plans when fully implemented will generate sufficient power for an area from Albany to Cape Reinga by harnessing the energy of the tide.

The harbour is one of the largest harbours in the world covering 900 square kilometres with 3,000 kilometres of shoreline. The Kaipara extends for 60 kilometres north to south.

Tidal turbines follow similar principles to wind turbines, except that it is possible to forecast the tides and therefore both the level of generation and the time of day for production of power. There are about ten companies constructing tidal turbines and others joining the industry, mainly from northern Europe and North America.

Tidal and wind power generation have many similarities, and some differences. Since sea water is 830 times denser than air the same velocity generates several hundred times more power in water than in air. In addition tidal turbines are totally submerged, invisible and silent.

The Kaipara Harbour has a number of factors making it suited to marine turbines. Up to 8,000 million cubic metres of water pass in and out of the harbour each day, which is the same as a cube of water 2 kilometres x 2 kilometres x 2kilometres. The harbour is rarely used for commercial shipping due to the treacherous tides and sand bars at its mouth.

The project maintains New Zealand’s tradition of harnessing renewable energy. Over half of New Zealand’s electricity is produced from hydroelectric, geothermal, wind and other sustainable sources.

Estimated total costs for the project over the first ten years are about NZ$600 million, offset by modest but growing revenues from year four.

Kaipara tides average 2.10 metres (seven feet). The Kaipara Harbour has a temperate climate: the average annual air temperature is 16ºC (61ºF). It is close to Auckland's 1.5 million residents, and to another large centre, Whangarei. There are readily available routes to sell electricity using existing transmission lines durng the earlier stages of the project.

Many bodies are actively involved in the management of Kaipara Harbour including Government departments, councils, community groups and tangata whenua.