A bit of history on the use of geothermal resources in NZ - just...

A bit of history on the use of geothermal resources in NZ - just in case some of you thought the concept was new.
This is just one of [I think 19] producing geothermal energy fields in NZ. You can do a google search and read more. Old technology, but the time may come when the new 'hot rock' technology will have its place in the Shakey Isles.

Kawerau
The Kawerau geothermal field is located immediately east of Kawerau township. Most of the surface thermal features are believed to have been in a natural state of decline prior to development, which arose from the energy requirements of the large Tasman pulp and paper processing plant built in the 1950s.
Seventeen wells (including redrills) had been completed by the end of 1957 when Kawerau became the first production field in New Zealand. In the late 1950s four of the wells were deepened following a decline in field production and further drilling commenced in 1966 after continued field decline. The Crown had an active drilling program from the mid-1970s through to mid-1980s, aimed both at maintaining steam supply to the mill and investigating a major expansion for power generation or other process steam supplies. Wells have required frequent cleanouts of calcite scale. New wells have occasionally been drilled to maintain supplies. Until the commissioning of the Ohaaki power station at Broadlands-Ohaaki, Kawerau was the second largest producing field in New Zealand and its steam supply for industrial use equates to half of the worlds total steam supply for industrial applications.
Downhole temperatures recorded in the field range from 250 to 310°C. A total available resource greater than 350 MWe has been estimated. Around 270 tonnes per hour of steam is provided to the Norske Skog Tasman mill where it is used for process heat, electricity generation and timber drying. In addition, Bay of Plenty Electricity operate two binary plants rated at a total of 6 MWe which use some of the separated geothermal water as a heat source. These are linked to separator plants physically either side of the Tarawera River. In 2004, Norske Skog Tasman replaced their existing geothermal turbo-alternator with a refurbished ex-US Navy 8 MWe turbo-alternator.
Wells at Kawerau tend to suffer rapid run-down due to mineral deposition and cold water inflow. Various measures are used to maintain output. Production from the field has adversely affected the already declining natural features. Most waste water from the field is discharged into the Tarawera River after passing through a cooling channel, and current resource consents require ongoing efforts to reduce brine discharge. Re-injection of a limited quantity of fluid is undertaken. Future development options at Kawerau are constrained by the need to maintain steam supply to the Tasman processing plant. From 2004, Mighty River Power began an exploration programme in a new area of the Kawerau field. In 2005, a consent application was lodged by Mighty River Power for the development of a 70-80MW power station (See external site). Consents have been granted and Mighty River Power is now installing the largest single condensing geothermal turbine in New Zealand’s history.
In July 2005 after careful negotiation, the Crown transferred wells, steamfield equipment and contracts to Mighty River Power, who had a back-to-back transfer arrangement with Ngati Tuwharetoa Geothermal Assets. The negotiations involved a balancing of government commitments, Treaty obligations and commercial interests. The transfer marks a change from what has been a caretaking role to a development focus.
The resource is regulated by Environment Bay of Plenty.