Manapōuri is a hydro electric power station located at the west end of Lake Manapōuri in Fiordland National Park, South Island, New Zealand.
Completed in 1972, Manapōuri was built primarily to supply electricity for the Tiwai Point aluminium smelter near Bluff, some 160 km (99 miles) to the southeast. The station utilises the 230-metre (750 ft) drop between the western arm of Lake Manapouri and the Deep Cove branch of the Doubtful Sound 10 km (6.2 miles) away to generate electricity. The construction of the station required the excavation of almost 1.4 million tonnes of hard rock to build the machine hall and a 10 km tailrace tunnel. A second parallel tailrace tunnel was completed in 2002 to increase the station's capacity.
Picture by Christopher Erdal, 2016
The original turbines were designed by Allis-Chalmers and manufactured by Harland Engineering Co., Alloa, the first two turbines being operational in September 1969. These turbines were replaced after decades of service with new units from General Electric Canada, however a part of one of the Harland turbines has been kept as a display item.
Picture by Christopher Erdal, 2016
Following this two-stage refurbishment, the station has seven 122* megawatt generating units, and an operating maximum station output of 854 megawatts. Manapōuri generates enough electricity each year for about 619,000 average New Zealand homes. Manapōuri is the largest hydro power station in New Zealand.
* sign in the picture above appears to be mistaken at 133 MW per turbine. All other sources claim 122MW each and 854 MW total.
Building Manapōuri
The original construction of the Manapōuri hydro station was a huge engineering achievement. The project took 1,800 workers eight years to complete in extremely harsh conditions. The project involved constructing the power station 200 metres below a granite mountain in an underground cavern.
Several access and service tunnels were built. The 10-kilometre tailrace tunnel was excavated to take the water that flows out of the station into Deep Cove in Doubtful Sound.
All this was completed using drill and blast excavation methods to carve through the hard Fiordland rock.
The first power was generated in September 1969, with the installation of two generating units. The station became fully operational in 1972 when the seventh and final generating unit was commissioned.
In 1998, work began on the second tailrace tunnel. An additional outlet for the station was drilled, allowing it to generate to its full rated capacity.
In 2002, the second tailrace tunnel was completed. It runs parallel to the original 1970s tunnel.
In 2005, new turbines were fitted which allows the station to achieve a maximum continuous rating of 854 megawatts, although resource consent conditions limit generation to 800 megawatts.
Key dates
1964 Construction begins
1972 Manapōuri fully operational
2002 Second tailrace tunnel completed
2007 Turbine replacement completed.
References
Christopher Erdal
Meridian Energy
Wikipedia - Manapouri Power Station