Huntly Power Station Plants

Units 1 - 4

The original Huntly Power Station was built between 1973 and 1985, when the last of the four 250MW units was commissioned. The 1,000MW steam power plant is made up of four identical 250MW units, which consist of a boiler and a turbine. Fuel (either coal and/or gas) is burnt inside the boiler furnace, which generates steam at 540°C and 184 Bar or 2,700 PSI pressure. The steam is piped to the turbine which drives a generator. Once the energy in the steam has been extracted in the turbine, it then is condensed back to water and pumped back to the boiler in a closed cycle. Ash from the combustion of coal is removed from the flue gas by electro-static precipitators.

The original steam plant uses water from the Waikato River to cool the condensers. The resource consent requires that the maximum temperature of the river downstream of the station is less than 25°C. During summer, when the river temperature upstream of the station can exceed 24.5°C, the station must reduce the generation to remain within the temperature constraints. This has meant that Huntly Units 1 - 4 has been reduced to 0MW total output at times on very hot days. To alleviate this problem Genesis Energy constructed a "helper" cooling tower, which cools the water before it discharges back to the river. This cooling tower enables one 250MW unit to generate to 150MW of power, irrespective of the river upstream temperature.

Unit 5

Huntly Unit 5 (formerly e3p; Energy Efficiency Enhancement Project) uses natural gas as its fuel source, and is able to generate up to 400MW of electricity - enough to power approximately 400,000 households. The high efficiency gas -fired unit was commissioned in June 2007. The unit is a high-efficiency combined cycle generator consisting of four major components.

• 250MW industrial gas turbine made by Mitsubishi Heavy Industries.
• HRSG or heat-recovery steam generator.
• 135MW steam turbine

Its combined cycle technology is regarded as the most technically advanced means of converting natural gas into electricity that is available today. This combination of high efficiency and lower CO2 emissions has enabled Genesis Energy to reduce its CO2 intensity from the Huntly Power Station site as a whole.

Unit 6

This 48MW Gas Turbine unit consists of a General Electric gas turbine (LM6000), which drives a generator via a gearbox; it was commissioned in June 2004.