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 Geothermal Energy and Electricity Generation
Geothermal energy produces about 7% of New Zealand's electricity supply. Most of New Zealand's installed geothermal generating capacity of over 400 MWe is situated in the Taupo Volcanic Zone, with another 10 MWe installed at Ngawha in Northland. The temperature and conditions of a particular geothermal reservoir determine which type of generation technology is used: dry steam, flash steam or binary cycle.

Cooling tower at Ohaaki geothermal power stationWhen the first generator was commissioned at Wairakei in 1958, it was only the second geothermal plant in the world to begin large-scale commercial operation and the first to exploit a wet (rather than dry steam) geothermal resource. The impetus for the development of Wairakei came in 1947 from severe electricity shortages following two dry years which restricted hydro generation, and a desire by the New Zealand Government for the electricity supply to be independent of imported fuel. New Zealand is now faced with a similar situation which geothermal energy has the potential to alleviate.

There are currently six fields used for geothermal electricity generation, which is dominated by Contact Energy Ltd (a listed company) and Mighty River Power (a State Owned Enterprise). A significant factor in recent geothermal projects has been the high level of commercial participation by Maori-owned enterprises.

Historical Changes in NZ Geothermal Electricity Generation Capacity

Plant Name Current Owner 'Commissioning' Date Installed
Capacity
(MWe) 		Cumulative
Capacity
(MWe)
Wairakei Contact Energy 1958-63 193 193
Kawerau Norske Skog Tasman 1966 10 203
Wairakei Contact Energy 1982 -36 167
Kawerau Binary (TG1) Bay of Plenty Electricity 1989 2.4 169
Ohaaki Contact Energy 1989 114* 283
Kawerau Binary (TG2) Bay of Plenty Electricity 1993 3.5 287
Ohaaki Derating Contact Energy 1996 -10 277
Wairakei BP Contact Energy 1996 5 282
Poihipi Road Contact Energy 1996 55** 337
Rotokawa Mighty River Power 1997 29 366
Ngawha Top Energy 1998 10 376
Mokai 1 Tuaropaki Power Company 1999 55 431
Ohaaki Derating Contact Energy 2001 -38 393
Rotokawa Extension Mighty River Power 2003 6 399
Kawerau BP Decom Norske Skog Tasman 2004 -10 389
Kawerau BP2 Norske Skog Tasman 2004 8 397
Wairakei Binary Contact Energy 2005 14.4 411
Mokai 2 Tuaropaki Power Company 2005 39 450
Ohaaki Derating Contact Energy 2005 -16 434

* Although Ohaaki still has 114 MWe of plant installed on site, high pressure turbines are now decommissioned and only one of the two remaining turbines is operating. The station generates between 30 and 40 MWe due to field limitations. Some additional Ohaaki drilling has been undertaken to fully load the remaining turbine.
** Poihipi Road generation has been restricted by resource consent limitations.

While future installed capacity is unknown, developers have been talking of further development of the order of 400 MWe over the next 10 years. This is based on the resource potential, assumed consenting restrictions and the industry's capability to build the plant.

See Other Geothermal Energy Content