Manapouri Power Station

The Manapouri Power Station is located on the West Arm of Lake Manapouri. Our boat ride across the lake ended there. Above ground only the transmission towers and intake tunnels are visible:

Lake Manapouri is 178 meters above sea level. It is this difference which provides the power to drive the turbines. The turbines are located underground, 176 meters lower than the surface of the lake. Water falls down the nearly vertical penstocks to power the turbines, and then 10 km out to sea, at Doubtful Sound, through two nearly horizontal tailrace tunnels.

Access to the turbine room is by tunnel. We rode a coach bus down this tunnel:

The tunnel is 2 km long and spirals around one and a half times while dropping 200 m.

In the turbine room at the bottom are seven generators:

Each generator is rated at 121.5 MW which puts the total capacity at 850 MW. For reference, Vermont Yankee is 620 MW and the Hoover Dam is 2080 MW.

The Manapouri Power Station is the largest hydroelectric plant in New Zealand and generates about 14% of the total electrical power in the country. The facility was built specifically to power an aluminum smelter 171 km away in Bluff on the south coast. The smelter uses most of the station's output, and the rest goes into the national grid.

The Visitors Center had this scale model of the facility:

Note the curving access tunnel, the seven vertical penstocks (the larger vertical tubes), and the two nearly horizontal tailrace tunnels. The turbine room is the orange horizontal cylinder at the bottom of the penstocks. The seven smaller vertical tubes are cable shafts to bring the power to the surface.

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