Ohaaki Power Station

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The Ohaaki Power Station is a geothermal power plant owned and operated by Contact Energy. A distinctive feature of this power station is the 105 m high natural draft cooling tower, the only one of its kind in New Zealand.

Although initially constructed to generate 104 MW, decline in thesteamfield has meant maximum net capacity is about 65 MW with an annual output of around 400 GWh pa.

There are currently three turbines in operation. One smaller turbine runs off high pressure steam which then backfeeds into the main intermediate pressure system that feeds the two main units. Condensers on the back end of the main turbines are fed cooled water from the cooling tower to condense the steam back into water. Additional condensate gained in this process is reinjected back into the ground.

The Ohaaki geothermal power plant is located adjacent to theOhaaki Marae (Ngāti Tahu) on the banks of the Waikato River in New Zealand. Gradual sinking of the marae has been attributed to draw-off of geothermal fluids by the power station. The area of the marae is sinking approximately 170mm a year. In the 1960s, the marae was moved to its present location because the previous site was flooded when the dam for the Ohakuri Power Station was filled.

OHAAKI POWER STATION
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LOCATION	Waikato
OWNER	Contact Energy
STATUS	Operational
FUEL	Geothermal
MAXIMUM CAPACITY	104 MW
COMMISSIONED	1989

Nga Awa Purua Power Station

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Nga Awa Purua is a geothermal power plant located nearTaupo in New Zealand. The project was developed by Mighty River Power. Nga Awa Purua is New Zealand's second largest geothermal power station and the steam turbine is the largest geothermal turbine in the world.

The geothermal power plant is a joint venture between Mighty River Power and the Tauhara North No 2 Trust. The $430 million project first generated electricity on 18 January, and was officially opened by Prime Minister John Key on 15 May 2010.

The Rotokawa Power Station is situated close by.

NGA AWA PURUA
LOCATION	Waikato
OWNER	Mighty River Power
STATUS	Operational
FUEL	Geothermal
TURBINES	1
MAXIMUM CAPACITY	140 MW
COMMISSIONED	2010

Wairakei Power Station

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

The geothermal power plant was built in 1958, the first of its type in the world, and it is now being 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. This increased the total capacity of the power station to 181MW. The Wairakei power station is due to be phased out from 2011, replaced by the Te Mihi geothermal power station. The PoihipiPower Station was built in 1996 at a nearby site in the same field.

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. So far, 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. 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. Also, the Waikato river water is already too high in arsenic content to be safe to drink without special treatment, and so reinjection of the facility's water does not exacerbate this problem.

WAIRAKEI POWER STATION
$Description: C:\Users\Admin\Desktop\Size Reduced assets\Size reduced\Powerplant Engg\assets\geothermal_power\24_files\image010.webp$ The Wairakei Power Station, with the main two blocks at the left rear. The binary plant is in front.
LOCATION	New Zealand
OWNER	Contact Energy
FUEL	Geothermal
MAXIMUM CAPACITY	181MW
COMMISSIONED	1958
DECOMMISSIONED	2011 onwards (planned)