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Wairakei Power Station

From Wikipedia, the free encyclopedia

Wairakei Power Station
The Wairakei Power Station, with the main two blocks at the left rear. The binary plant is in front.
Map
CountryNew Zealand
LocationWairakei, north of Taupō
Coordinates38°37′37″S 176°06′19″E / 38.62694°S 176.10528°E / -38.62694; 176.10528
StatusOperational
Commission dateNovember 1958 (November 1958)
Owner(s)Contact Energy
Geothermal power station
TypeFlash steam with binary cycle[1]
Wells55 production
6 reinjection
50 monitoring[1]
Max. well depth660 m (2,170 ft)[1]
Power generation
Units operational6× 11.2 MW
3× 30 MW
1× 4 MW
1×14 MW binary
Nameplate capacity175 MW
Capacity factor89.0%
Annual net output1365 GWh[1]
External links
CommonsRelated media on Commons

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

YouTube Encyclopedic

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  • Geothermal power at Wairākei - Roadside Stories
  • Volcanic Power (1962)
  • Geothermal Power station
  • New Zealand Geothermal Plants
  • Pictorial Parade No. 82 (1958)

Transcription

[Audio (13 secs): Sound of boiling mud] [Narrator] Columns of steam at Wairākei, just north of Taupō, sometimes waft across the highway, letting travellers know that they are in one of the most active geothermal areas in the world. A lot of New Zealand's electricity is produced through renewable sources, such as hydro-power. However, after severe droughts in the late 1940s, the government set about harnessing the geothermal potential at Wairākei. Geothermal power was seen as a good alternative because unlike hydro, solar, and wind power, it is not affected by the weather. Construction began in 1958 and when it was completed in 1963, Wairākei was only one of two geothermal stations in the world. There are now eight geothermal power stations in New Zealand alone. Despite providing a reliable and cost-effective electricity supply, geothermal power stations can have a detrimental effect on the environment. When the Wairākei scheme started extracting heat from the ground, there was an immediate decline in geothermal activity in the area. The ground sagged in some places, and hot springs and geysers began to die as the supply of steaming water from below was depleted. In Geyser Valley, the famous Wairākei Geyser, which had been attracting tourists since the 1880s with its water spouting up to 42 metres high, stopped completely. Then the famous Champagne Pool, a boiling spring with a blue tint, dwindled away. Geyser Valley continued to deteriorate, and in 1973 it was shut down as a tourist attraction. Extracting geothermal fluids can also reduce the pressure in underground reservoirs and cause the land to sink. At Wairākei, the centre of the subsidence is sinking at a rate of almost half a metre every year. In 2005 this ground was 14 metres lower than it was before the power station was built. Geothermal fluids contain some toxic elements. If waste is released into rivers or lakes instead of being injected back into the geothermal field, these pollutants can damage aquatic life and make the water unsafe for drinking or irrigation. However, The Craters of the Moon near Wairākei have actually seen a boost in geothermal activity because the underground pools have got hotter and now produce more steam. This is now one of only a few thermal areas still active in the Wairākei geothermal field. Most of New Zealand's geothermal energy goes to produce electricity, but it can be used for any processes where heat is required. The world's only geothermally heated prawn farm was established in 1987 on the banks of the Waikato River, next to the Wairākei power station. The first giant river prawns, which require warm temperatures of around 26 degrees centigrade, were imported from Malaysia in 1988. By 2005 the farm was producing about 20 tonnes per year. The prawn farm heats its water with heat from Wairakei power station's waste water before it flows back into the Waikato River. The prawns live for nine months before being harvested and sold exclusively to local restaurants This is a good example of what is known as 'cascade use', where geothermal heat has a function past its primary purpose. Cascading improves the overall efficiency of a resource by using its waste products. In the case of the prawn farm, cascading also reduces the discharge of hot water into the river, where it can harm aquatic life. Geothermal waters are also used for heating greenhouses for the production of vegetables, flowers and fruit. A tropical orchid, Phalaeopsis, is grown in large, geothermally heated greenhouses, using waste heat from the nearby Wairākei power station. The warm atmosphere inside the greenhouse mimics the monsoon conditions of the orchid's natural habitat.

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 181 MW.[1] The Wairakei power station is due to be phased out in 2026, replaced by the Te Mihi geothermal power station.[4] The Poihipi Power Station was built in 1996 at a nearby site in the same field.[2]

Electricity Generation at Wairakei.

Units

Wairakei A station

  • Unit 1 – 11.2 MW intermediate pressure
  • Unit 4 – 11.2 MW intermediate pressure
  • Unit 7 – 11.2 MW low pressure
  • Unit 8 – 11.2 MW low pressure
  • Unit 9 – 11.2 MW low pressure
  • Unit 10 – 11.2 MW low pressure

Units 2, 3, 5 and 6 were decommissioned in 1984.

Wairakei B station

  • Unit 11 – 30 MW intermediate/low pressure
  • Unit 12 – 30 MW intermediate/low pressure
  • Unit 13 – 30 MW intermediate/low pressure

Wairakei Unit 14 – 4 MW intermediate/low pressure

Wairakei Binary Plant – 14 MW binary

Effects

Pipes running from the Power station

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. The majority of arsenic in the Waikato River comes from the geothermal power station with the concentration reaching 0.035 grams of arsenic per cubic metre in certain places. The amount of arsenic gradually declines as the river flows northwards and is at its lowest at the Waikato River Heads.[5][6]

Transmission

Wairakei Geothermal Valley Steam Pipes

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. A 33 kV connection at the substation supplies Unison Networks' Taupō distribution network.[7]

See also

References

  1. ^ a b c d e "Geothermal" (PDF). Contact Energy. Archived from the original (PDF) on 2010-06-04. Retrieved 2008-10-23.
  2. ^ a b c "Geothermal Fields". New Zealand Geothermal Association. Archived from the original on 2013-06-28. Retrieved 13 March 2011.
  3. ^ "Geothermal Energy and Electricity Generation". New Zealand Geothermal Association. Archived from the original on 2016-01-14. Retrieved 13 March 2011.
  4. ^ "Contact Energy to replace Taupō geothermal ststions". Radio New Zealand. Retrieved 4 August 2023.
  5. ^ Arsenic in the New Zealand environment - Brett Robinson, Brent Clothier, Nanthi S. Bolan, Santiago Mahimairaja, Marc Greven, Christopher Moni, Monica Marchetti, Carlo van den Dijssel and Georgina Milne - Institute of Natural Resources, Massey University, Palmerston North, New Zealand
  6. ^ Inflows of geothermal fluid chemicals to the Waikato River catchment, New Zealand - M.H. Timperley and B.A. Hauser, New Zealand Journal of Marine and Freshwater Research, 1996: Vol 30: 525-535.
  7. ^ "Chapter 11: Central North Island Regional Plan - Annual Planning Report 2012" (PDF). Transpower New Zealand Limited. March 2012. Retrieved 1 July 2012.

Further reading

  • Martin, John E, ed. (1991). People, Power and Power Stations: Electric Power Generation in New Zealand 1880 - 1990. Wellington: Bridget Williams Books Ltd and Electricity Corporation of New Zealand. pp. 316 pages. ISBN 0-908912-16-1.

External links

This page was last edited on 17 August 2023, at 01:17
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