Energy and extraction

Geothermal energy is an important contributor to New Zealand’s electricity supply. But extracting geothermal energy affects the geothermal features and the surrounding environment. Reusing and reinjecting geothermal energy and fluid, and managing the geothermal system as an integrated whole to development helps to minimise the effects.

On this page: How much we use, Where the power stations are, What extraction does, Reducing the effects

How much we use

Primary energy – In 2005, New Zealand’s total primary energy supply was 702 petajoules (PJ). Twelve percent (85 PJ) of New Zealand’s primary energy came from geothermal sources¹.

Primary energy comes directly from natural sources such as the sun, gas and oil, wood, coal and geothermal energy:

• Industries use it for process heat.
• Gas is used in vehicles and for cooking and heating.
• Households use it for heating (burning wood and coal, using geothermal heat and water).
• It is also turned into electricity.

Primary energy obtained from geothermal sources is forecast to increase to 150 PJ in the next 25 years². Estimates say we could extract between 30,000 and 57,000 PJ per year of geothermal energy using present technology³. But this could lead to irreversible effects, such as the destruction of geysers and other surface features, and land subsidence.

Electrical energy - In 2005, New Zealand’s total electrical energy supply was 150 PJ per year. Geothermal energy provided around 6.5 percent of our national electricity supply, most of it coming from the seven geothermal power stations in the Waikato region¹.

Waikato region - The Waikato region provides 90 percent of the primary geothermal energy extracted in New Zealand⁴. Of the geothermal energy extracted, only 10 percent is converted to a useable form¹. The rest is re-injected or disposed of into the environment as heat. In the Waikato region there are about 40 separate industries, accommodation facilities and tourist facilities take small amounts of heat for direct uses.

Where the power stations are

New Zealand has nine geothermal power stations. Seven are in the Waikato region. There are plans to build others and expand existing stations, in the Waikato, Bay of Plenty, and Northland regions. The table below lists the stations in our region.

Geothermal power stations

As well as these large power stations, about 40 commercial operations extract small or medium quantities of geothermal water and energy in the region. Most operations take the water from wells or springs, but others take water from hot streams such as the Onekeneke at Taupo. This heated water is used mainly for public baths or motel pools.

Geothermal systems extend under large areas of land. To find, develop and extract these economic sources of geothermal energy and fluid resources (sometimes as deep as five kilometres below the Earth’s surface) requires large capital investment and complex infrastructures.

What extraction does

Although only a fraction of geothermal energy is currently used, the environmental effects have been dramatic.

Since the 1950s, the number of geysers in the region has dwindled because of heat and fluid extraction and the effects of overlying land uses. When water extraction prevents pressure from reaching the level necessary to fuel the geysers, they disappear. As a result, many sinter-depositing springs and geysers and their associated ecosystems have been lost with the development of the Wairakei Geothermal Power Station.

Use our map to find out more about the state of geothermal features in the Waikato region.

The extraction of heat and fluid also causes land subsidence. For example, a marae near Ohaaki Geothermal Power Station is sinking and runs the risk of being inundated by the Waikato River, as the ground around and under it subsides.

Effects on other parts of the natural environment are summarised in the table below.

Environmental effects of geothermal contaminants⁵

Find out more about the arsenic levels in the Waikato River.

Reducing the effects

In the past, once geothermal fluid extracted for electricity generation had been through the power station, any excess heat and fluid was discarded. Now increasingly, other industrial and domestic processes use the discarded heat and fluid. This means less of the energy extracted is wasted, and less heated water is produced as a by-product. For example:

• A prawn farm near Taupo heats its own freshwater by running it across pipes containing geothermal water used by its neighbour, the Wairakei Geothermal Power Station.
• At Ohaaki, geothermal heat is used to treat timber.

Developers must obtain resource consents prior to developing geothermal areas. The resource consent process requires consultation with iwi and considers potential effects on waahi tapu and other significant sites. Significant adverse environmental effects must be avoided, remedied, or mitigated.

Each power station needs a set of about 15 resource consents to cover such activities as taking geothermal fluid and fresh water, and discharging steam and other gases to air, reinjection of geothermal fluid to ground or its discharge to land or water, drilling geothermal wells, and building and maintaining roads.

Find out about how the Mokai Geothermal System is being managed.

Footnotes

1. New Zealand Energy Data File January 2006, Ministry of Economic Development
2. NZ Energy Outlook to 2030, August 2006, Ministry of Economic Development
3. Lawless, J. and Lovelock, B, 2001. New Zealand’s Geothermal Resource, in New Zealand Geothermal Association 2001 Seminar Proceedings.
4. Sinclair Knight Merz Ltd, 2006: Regional renewable energy assessment : Waikato region, Sinclair Knight Merz Ltd.; Energy Efficiency and Conservation Authority (EECA), 2006
5. Drinking water standards referred to in this table are defined in: Ministry of Health.2005: Drinking Water Standards for New Zealand 2005. Ministry of Health, Wellington.
6. New Zealand Geothermal Association Submission to Government on Climate Change Consultation Paper, May 2002.
7. National Institute of Water and Atmospheric Research. 1995: Mercury and Arsenic in Waikato River Fish. NIWA Consultancy Report SCJ129/06. NIWA, Hamilton.

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