ELECTRICITY

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Wairakei on the banks of the River. Pioneer Station Still Abundant Electricity Supplier

The world’s first Mike Dunstall, General Manager of Geothermal Resources and KEY BENEFITS: geothermal power Development at , says station to use wet “The construction of saw • Renewable energy source become the second • Minimal greenhouse steam technology largest producer of , gas emissions and a pioneer in the field.” was commissioned • Generates base load in 1958 at Wairakei, “Since 1960 has electricity which is not been running at 90% or more of its impacted by weather north of Taupō. maximum output and is an important base load station, providing constant electricity to over one hundred KEY FEATURES: thousand homes. Just recently, we have reduced our utilisation of the • Operational for over 60 years oldest Wairakei machines, as our new • 175 MW installed capacity Te Mihi station takes over some of Wairakei’s role” • 1000 GWh of electricity per annum Wairakei’s 25 km2 borefield contains over 150 wells, with a typical depth of 600 m in older wells and as deep as 3000 m in newer wells. Of these, about 65 are in production, extracting hot water and steam from the earth at a rate of 245,000 tons per day, while twenty are injection wells that put about 180,000 tons of water back into the field daily. “WAIRAKEI PAVED THE WAY FOR NEXT GENERATION POWER STATIONS, LIKE TE MIHI. IT HAS PROVEN THAT GEOTHERMAL IN NEW ZEALAND IS ONE OF OUR BEST RENEWABLE AND CLEAN ENERGY RESOURCES AND THE TECHNOLOGY FIRST DEVELOPED AT WAIRAKEI CONTINUES TO INFLUENCE GEOTHERMAL POWER STATION DESIGN AROUND THE WORLD.” Wairakei borefield, where the hot steam is drawn from.

“Reinjection reduces effects on the reduced to 1.1 bar. This steam then Since started , where up to 36,000 tons travels through the second low pressure running in 2013, Wairakei has been of separated geothermal water passes part of the turbine before finally reaching reduced in output and is not likely to run daily, and can help manage the life of the the condenser. past 2026 (when its resource consent geothermal field.” Contact Energy is in runs out). Over time, steam utilisation will The binary plant, added in 2004, is the process of bringing river discharges shift to the more modern power plants a modern extension to the Wairakei back to levels that flowed naturally on the Wairakei steam field. Power Station. before the power station was built. Advances in binary technology have Contact Energy is continuing to allowed lower temperature geothermal develop further reinjection to reduce waste water (brine) to be utilised. The river discharges back to levels that design uses a heat exchanger with an flowed naturally before the power isopentane working fluid in the generator. station was built. The isopentane has a very low boiling There are currently 12 electricity point. When heated by previously generators available for service; four unused geothermal water, this working are low pressure, two intermediate fluid easily drives the turbines. The pressure, three mixed pressure, one isopentane is then condensed and intermediate low pressure and two passed back to the heat exchangers to within the binary plant. begin the cycle again. This binary plant The low pressure turbines utilise steam has added another 14 MW of capacity, at 1.1 bar (where the atmospheric using otherwise waste brine to produce pressure is 1 bar), so condensers have electricity. to effectively pull the steam through for Mike says that geothermal is Geothermal steam pipes carry steam to the the turbines to spin. New Zealand’s most reliable, renewable power station. The condensers use cold water from energy source and is comparatively a the Waikato River, which is sprayed into very clean energy. a chamber at the turbine exit. As the “Geothermal is the most reliable source steam condenses it forms a vacuum, of renewable energy, as it is not pulling more steam through. The low influenced by weather. It is also pretty temperature of the water used partly low in environmental impact. There is results in Wairakei’s high efficiency, some carbon dioxide emission from comparable to more modern geothermal Wairakei, but this is many times lower power stations. than fossil fuel plants would emit to Intermediate pressure turbines work on generate the same power. Since 2012 Mike Dunstall a similar principle but use 3.5 bar steam we have also included a bioreactor in General Manager instead and pass their steam on to two the steam condensate system, as part of Geothermal Resources and Development of the low pressure turbines. the changes we are making at Wairakei Contact Energy Ltd. to reduce the impact of steam and hot Wairakei Power Station The mixed pressure turbines are an State Highway 1 water releases to the environment”. intermediate pressure turbine followed Taupō by a low pressure turbine. The steam As the first wet steam geothermal power New Zealand enters the first section at 3.5 bar, it then station and now nearly 60 years old, Phone: +64 (0)7 376 0500 loses some energy as electric power is Wairakei is still running strong. Email: [email protected] generated resulting in its pressure being Website: www.contactenergy.co.nz

New Zealand requires reliable, renewable energy sources into the future. Wairakei Research Centre The Government is supporting GNS Science in fostering increased use of 114 Karetoto Road, renewable resources. By 2025, the Government’s Energy Strategy aims Wairakei 3377 for direct use of geothermal energy to account for more than 12 PJ/year. Private Bag 2000, For more information visit our website: Taupo 3352 New Zealand www.gns.cri.nz/earthenergy Phone: +64 7 374 8211 or contact us: Email: [email protected]