GEOTHERMAL_ENERGY_tapping.png Nesjavellir Geothermal Power Station

Geothermal Energy in New Zealand

Geothermal energy is renewable and sustainable, as it is energy generated by heat deep inside the earth. This is harnessed by geothermal power stations, which pipe geothermal fluid (which is a mixture of high pressure water and steam) from wells deep in the earth. The geothermal fluid is then turned into steam, which powers turbine generators to produce electricity. The leftover geothermal fluid is then pumped back into the ground.

How a geothermal power plant works

New Zealand is perfect for geothermal energy, as it is on the boundary between two tectonic plates. This means that the earth’s crust is thinner, and the hot mantle is closer to the surface. New Zealand has five geothermal power stations, which are all located in the Taupo and Kawerau regions. These are the Ngatamariki, Te Mehi, Wairakei, Ohaaki and Rotokawa geothermal power stations. The steam fields cover an area of 25 square kilometres.

Geothermal Energy is the third largest contributor to New Zealand’s energy supply, and the largest renewable energy supplier. The Wairakei Power Station produces 1550 GWH of electricity per annum, which is 4.3% of New Zealand’s electricity production, and is enough to supply Taupo, Rotorua, Napier and Hamilton.

Wairakei Geothermal Power Station

Geothermal energy was traditionally used by the Maori for cooking, heating and therapeutic purposes. Today, geothermal energy is used by local industries in the Taupo and Kawerau regions, for pulp and paper mills, timber drying, heating and hot water heating, horticulture, milk-drying, and tourism, such as the Huka Prawn Park near Taupo, which is the only geothermal-heated prawn park in the world. One of the best things about geothermal energy is that it is extremely reliable and consistent, unlike most other renewable energy forms. Geothermal energy operates at 90% of its capacity all the time, whereas hydro and wind power stations only operate at 30-50% of their capacity. Another benefit with geothermal power stations is the partnerships between the geothermal companies and Maori trusts. Maori have land access rights to geothermal fields, and having geothermal projects create economic benefits to local iwi.

Although geothermal energy is mostly clean, it still does produce some greenhouse gases. Gases like hydrogen sulfide, carbon dioxide, methane and ammonia can be released from the ground when extracting geothermal fluid. Even though geothermal energy is sustainable, geothermal areas can cool down, and can be depleted if geothermal fluid is removed too quickly, and not replaced. Removing geothermal fluid from areas can also result in land subsidence. A possible future solution to the cooling of geothermal areas would be to harvest geothermal energy right from the magma, although the technology for doing so is still being developed. Geothermal energy is also very location specific, and the plants require a large area of land. Geothermal plants have a big impact on the land due to bores and piping.

© Sara Sutherland 2018