Primary industry: Riding the dragon, geothermal energy

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The power under the ground

Geothermal energy currently produces about 13% of New Zealand's electricity supply, about 750 megawatts of electrical power. Most of it comes from the Taupo Volcanic Zone, with another 25 megawatts installed at Ngawha in Northland. ?

The first generator was commissioned at Wairakei in 1958, making New Zealand only the second nation to begin commercial geothermal power production. Part of the inspiration for this was severe electricity shortages in 1947, when two dry years restricted hydro-generation, a situation that returned in 2008. ?

The good news is that there is significant scope for expansion of geothermal energy in New Zealand. The latest estimate is that there is approximately another 1,000 megawatts of geothermal potential. There is also significant potential for the direct use of geothermal heat. Because most electricity generation requires high temperature resources, it is possible to use the gradually-cooling geothermal fluid in a number of other applications as well, including greenhouses, timber-drying, aquaculture or even directly heating homes.

The cooled liquid can then be re-injected into the geothermal area to be reheated.?Mighty River Power is one of the big players in turning that potential into power, and it is expanding rapidly.

Over the past five years, the company has invested $1 billion into new geothermal developments, including shelling out $466 million this year to construct the new Ngatamariki geothermal plant near Taupo, which is due to be commissioned in 2013. Mighty River Power currently operates more than 380 megawatts of geothermal generation, with another 82MW currently under construction.?And the firm's reach is spreading well beyond these shores.

Geothermal power presently supplies the world with 10,715 Megawatts of electricity in 24 countries on six continents. But the potential to use geothermal resources is much greater. With the technology available today and under development for the future, it is estimated that geothermal resources could supply more than 300,000 Megawatts of power, while producing far fewer carbon emissions than fossil fuels.?

Mighty River Power committed US$250 million to international geothermal investment through GeoGlobal Energy in early 2010, which is pioneering the identification and development of new geothermal fields around the world.

The firm currently has interests in a 50MW project in the Imperial Valley Southern California, due to be operating in the first half of 2012; is partway through a drilling programme to confirm the resources available on the Tolhuaca geothermal field in Chile; and is well advanced with development opportunities in Bavaria in Germany.?

Doug Heffernan, chief executive, said: "Mighty River Power's geothermal experience is recognised around the world and this has opened up opportunities for us to make informed investments in international geothermal projects."?New Zealand's consultants in this field have also become hot property as on geothermal projects.

Geothermal boffins from global consultants Sinclair Knight Merz have been involved in developing more than 2,500MW of geothermal plants, about a quarter of the world's installed geothermal capacity. Much of this is based on expertise gained in our own volcanic landscapes.

HOW IT WORKS

Under the earth's crust, the magma, the layer of hot and molten rock continually produces heat, mostly from the decay of naturally radioactive materials such as uranium and potassium.

The amount of energy beneath the earth's surface is estimated at 50,000 times more energy than all the oil and natural gas resources in the world.

Due to the extreme heat the rocks start developing cracks and release energy.

To get that heat, water is pumped down an injection well. It then filters through the cracks in the rocks where they are at a high temperature.

The water then returns via the "recovery well" under pressure in the form of steam.

That steam is captured and is used to drive turbines.

Source: www.conserve-energy-future.com