The Underground Manapouri Power Station:
This is the largest hydro electric power plant in New Zealand:
It is housed underground in the Fiordland National Park in a cavern carved from rock almost 200 metres below the West Arm of Lake Manapouri. Unlike other hydro power stations, Manapouri does not have a high dam. It uses the natural 183 metre height difference between Lake Manapouri and the sea at Deep Cove in Doubtful Sound to generate electricity.
Over a hundred years ago, enormous potential was recognised for power generation using the water from the beautiful black Lakes, Manapouri & Te Anau. During the 1950s this potential was studied in detail. The discovery of Bauxite in Queensland, Australia led to growing interest in the idea of developing a cheap and reliable source of power for the process of Aluminium smelting. The N.Z. government at that time proceeded with discussions with Comalco. In 1960 it was announced that an agreement had been made between the Government and Comalco, giving the company a long-term, fixed contract for electricity until 2021. The project to build the Underground Power Station to supply electricity to the Aluminium Smelter to be built at Bluff got started in 1963. It took 1800 men 8 years to build, working 24 hours a day.
How the Manapouri Power Station works:
Water enters the Manapouri Power Station through intake gates and down large pipes, vertically, which are called Penstocks to drive the turbines. (photo beside - Click for enlargement) The water spins the turbines, which turns the Rotor, a part of the Generator. The Generator is made up of a spinning set of Magnets (rotor) inside a stationary set of Windings (stator) and this action creates electricity. The water then goes through the Draft Tubes and out the two Tailrace tunnels to Deep Cove in Doubtful Sound.