The Huntly power station is the largest thermal power station in New Zealand and is located in the town of Huntly in the Waikato. It is operated by Genesis Energy, a state-owned enterprise, and supplies around 17% of the country's power.
The Huntly power station consists of three separate generating plants - a 1000MW coal and gas-fired steam plant, a 50MW gas turbine generator, and a 385MW combined cycle gas turbine plant.
Each of the four original coal-fired units, installed in stages between 1973 and 1985, is capable of generating 250 MW (Megawatts) of electricity, giving a generating capacity of 1000 MW. Its chimneys are 150 metres high and each chimney has two flues that are 7 metres in diameter.
In 2004 the power station was upgraded with the addition of a 50MW gas turbine plant, and in 2007 the combined cycle gas turbine (CCGT) plant was commissioned. This plant increased the total generating capacity of Huntly by 385 MW (250 MW gas turbine + 135 MW steam turbine). The new turbine is a NZ$ 520 million investment and takes the total installed capacity to 1485MW.
The coal used in the older section of the power plant is imported to 50% from Indonesia, and to 50% mined in New Zealand. The gas for the newer turbines comes from the Maui gas field in the Taranaki. Previous to the substitution of coal, Huntly used gas from the field to power the generation of the main units as well, but these were switched in the 1990s because of dwindling resources.
The station uses water from the Waikato River for cooling. However, in order to protect aquatic life, conditions are imposed by its resource consent (see Resource Management Act), specifying the quantity of water that can be removed by the station along with the maximum temperature of the water when returned to the river (25°C). These conditions mean that on very hot summer days the station cannot operate at maximum capacity, and has sometimes effectively been shut down. A new cooling tower has been built as part of expansion works at the site, which allows one 250 MW unit to run at full load even during such times.
The plant, as one of the biggest carbon dioxide greenhouse gas generators of the country, has repeatedly drawn the ire of ecologists and has been the focus of associated protests. A recent (late 2006) government report outlining future anti-climate change and energy policies was seen by the operator as a sign that the plant might have to be closed by 2015 under these plans, with around 10 years of design life still remaining. It was also noted that, that apart from being difficult to replace as a source of power (due to New Zealand's annually growing generation demand, especially around Auckland), such a decision would also be uneconomical for the foreseeable future, even if coal prices were to rise.