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Wairakei field

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Wairakei field

Wairakei Power Station
The Wairakei Power Station, with the main two blocks at the left rear. The binary plant is in front.
Wairakei Power Station
Location of Wairakei Power Station
Country New Zealand
Location Wairakei, north of Taupo
Coordinates

38°37′37″S 176°06′19″E / 38.62694°S 176.10528°E / -38.62694; 176.10528Coordinates: 38°37′37″S 176°06′19″E / 38.62694°S 176.10528°E / -38.62694; 176.10528

Status Operational
Commission date November 1958 (November 1958)
Owner(s) Contact Energy
Geothermal plant
Type Flash steam with binary cycle[1]
Wells 55 production
6 reinjection
50 monitoring[1]
Well depth 660 m (2,170 ft)[1]
Cogeneration? No
Turbines 6× 11.2 MW
3× 30 MW
1× 4 MW
1×14 MW binary
Power generation
Installed capacity 175 MW
Capacity factor 89.0%
Annual generation 1365 GWh[1]

The Wairakei Power Station is a geothermal power station near the Wairakei Geothermal Field in New Zealand. Wairakei lies in the Taupo Volcanic Zone.

History

The power station was built in 1958, the first of its type (wet steam) in the world, and it is currently owned and operated by Contact Energy. A binary cycle power plant was constructed in 2005 to use lower-temperature steam that had already gone through the main plant.[2][3] This increased the total capacity of the power station to 181MW.[1] The Wairakei power station is due to be phased out from 2013, replaced by the Te Mihi geothermal power station. The Poihipi Power Station was built in 1996 at a nearby site in the same field.[2]


Effects

The use of steam from the field has had a number of visible effects on the local environment. Visible geothermal activity has increased (due to changes in the water table / water pressure allowing more steam to be created underground, upsurging at places like Craters of the Moon), while there has also been some land subsidence and reduction in steam volumes from the field after some decades of use. Recent total electrical production has been sustained or increased with the investment in additional power stations such as the binary plant of 2005 designed for lower-temperature generation, but the total still does not reach the early power levels such as the 192MW reported in 1965 (NZED Annual Statistics), for instance. Some power stations in the field are now capped in their extraction capacities and a substantial part of the water / steam is being reinjected after use.[2]

The hot geothermal fluid that is extracted is originally cold rainwater that had percolated downwards and been heated by hot rock; pumping back the warm water that emerges from the exhaust of the generator system thus reduces the heat drawn from the ground. Also, the Waikato river water is already too high in arsenic content to be safe to drink without special treatment, so reinjection of the facility's water does not exacerbate this problem.[4][5]

Transmission

Also at Wairakei is a major electrical substation, owned by the national grid operator Transpower. The substation is a major switching point for the Central North Island, and is responsible for connecting more than half the country's geothermal power stations, several hydroelectric power stations, the electricity supply to the entire Hawke's Bay and Gisborne regions and half of the Bay of Plenty region, as well as the local Taupo area.[6]

See also

References

Further reading

External links

  • New Zealand Geothermal Association - Wairakei Power Station information page

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