The Wairakei Power Station is a

geothermal power Geothermal power is electricity generation, electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation i ...

station near the

Wairakei Wairakei is a small settlement and Geothermal activity, geothermal area 8-kilometres (5 mi) north of Taupō, in the centre of the North Island of New Zealand, on the Waikato River. It is part of the Taupō Volcanic Zone and features several nat ...

Geothermal Field in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. Wairakei lies in the

Taupō Volcanic Zone The Taupō Volcanic Zone (TVZ) is a volcano, volcanic area in the North Island of New Zealand. It has been active for at least the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs n ...

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 Contact Energy Limited is a New Zealand electricity generation, electricity generator, a wholesaler of natural gas, and a retailer of electricity retailing, electricity, natural gas, broadband and Liquefied petroleum gas, LPG. It is the second ...

. A

binary cycle power plant A binary cycle is a method for generating electrical power from geothermal resources and employs two separate fluid cycles, hence binary cycle. The primary cycle extracts the geothermal energy from the reservoir, and secondary cycle converts the h ...

was constructed in 2005 to use lower-temperature steam that had already gone through the main plant. This increased the total capacity of the power station to 181 MW. The Wairakei power station is due to be phased out in 2027, replaced by the Te Mihi geothermal power station. The

Poihipi Power Station The Poihipi Power Station is a geothermal power station owned and operated by Contact Energy. It is located on Poihipi Road near Taupō in New Zealand. The plant produces around 350 GWh pa, utilising geothermal steam from the Wairakei field, a ...

was built in 1996 at a nearby site in the same field.

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

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 Craters of the Moon may refer to: * Lunar craters, craters on the Earth's Moon * Craters of the Moon National Monument and Preserve Craters of the Moon National Monument and Preserve is a National monument (United States), U.S. national monumen ...

), while there has also been some

land subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

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. 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 Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

in the

Waikato River The Waikato River is the longest river in New Zealand, running for through the North Island. It rises on the eastern slopes of Mount Ruapehu, joining the Tongariro River system and flowing through Lake Taupō, New Zealand's largest lake. It th ...

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.''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. Wairakei_Geothermal_Valley_Steam_Pipes

Transmission

Also at Wairakei is a major

electrical substation A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station an ...

, 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 Hawke's Bay () is a region on the east coast of New Zealand's North Island. The region is named for Hawke Bay, which was named in honour of Edward Hawke. The region's main centres are the cities of Napier and Hastings, while the more rural ...

and Gisborne regions and half of the

Bay of Plenty The Bay of Plenty () is a large bight (geography), bight along the northern coast of New Zealand's North Island. It stretches from the Coromandel Peninsula in the west to Cape Runaway in the east. Called ''Te Moana-a-Toitehuatahi'' (the Ocean ...

region. A 33 kV connection at the substation supplies

Unison Networks Unison Networks Limited (Unison) is an electricity distribution based in Hastings, New Zealand. Unison owns and manages the electricity lines network in the Hawke's Bay, Rotorua and Taupō regions. The service area covers 12,000 km2. The ...

' Taupō distribution network.

References

External links

New Zealand Geothermal Association
- Wairakei Power Station information page {{Electricity generation in Waikato Geothermal power stations in New Zealand Taupō District Buildings and structures in the Taupō District