Thermal Generation
Thermal generation refers to the process of generating electricity by burning fuels. In the case of Genesis Energy's assets, these fuels are natural gas and coal.
Huntly Power Station is Genesis Energy's thermal power station and consists of six separate generating plants; Units 1 - 4, the original four separate generating units of 250MW each, which are capable of burning coal, natural gas or a combination of the two; Unit 5, the 400MW combined cycle gas turbine (previously known as e3p), and Unit 6, a 48MW open cycle gas turbine.
What are the environmental issues surrounding thermal power?
It is recognised that the Huntly Power Station impacts on the environment by way of:
- The discharge of emissions to air;
- The discharge of heated water (used to cool the generating units) to the Waikato River;
- The discharge of treated process waters to the Waikato River;
- Dust emissions from the storage of coal on land;
- The disposal of ash; and
- The aesthetic impact of the power station on Huntly township.
Genesis Energy takes its responsibilities to avoid, reduce or minimise the affects its generation activities has on the environment very seriously.
Staff monitor the environment around the Huntly Power Station, taking samples from around the station each month to check the air and water, and the Helper Cooling Tower cools the water used in generation by six to nine degrees before releasing it into the Waikato river. This ensures that the Huntly Power Station can still operate during summer months, while complying with the maximum river temperature consent conditions.
The Huntly Environment Team also plant predominantly native trees around the station to improve the environmental aspect and further reduce the amount of CO2 released into the atmosphere.
Further information about Genesis Energy approach to environmental management at its generation sites can be found on the Genesis Energy website www.genesisenergy.co.nz
How thermal generation produces electricity at Huntly Power Station
Units 1 - 4 at the Huntly Power Station can use coal, gas or both simultaneously as fuel to generate electricity. The coal is delivered to the station via conveyor belt or by truck. Gas comes from the Taranaki region. The electricity generators at Huntly Power Station need a source of mechanical power to spin them. This power is supplied by turbines that are turned by high pressure steam.
Coal is put into several large grinders, crushed into a fine powder and blown into big boiler furnaces. If gas is used, it is piped into the furnaces and then burned in the boilers. A series of pipes in the upper region of the burner contain water which turns to steam under the incredible heat produced by the burning coal and/or gas.
High-pressure steam passes through pipes into steam turbines, which spins the turbine blade and in turn rotates the generators which generate electricity. After the steam has passed through the turbines, it is cooled back down to water and used again.
The energy produced by the generators is passed through a transformer and into the national grid transmission lines which carry the electricity across the country. At sub-stations, the electricity passes through transformers again, converting it into voltage that can be used in homes, schools, offices and various industries.
How thermal electricity is generated at the Huntly Power Station
Huntly Unit 5 (e3p)
Huntly Unit 5 (e3p)
The combination of high-efficiency and lower CO2 emitting gas-fired generation has enabled Genesis Energy to reduce its CO2 emissions from the Huntly Power Station site by a third. In one year, Unit 5 can save up to 1.8 million tonnes of CO2 from being emitted into the atmosphere by displacing higher-emitting coal-fired generation.
Unit 5 is a combined cycle gas turbine (CCGT) power plant that has been built on the existing Huntly Power Station site and uses natural gas as its fuel source. Unit 5 can generate up to 400MW of electricity - that's enough to power approximately 400,000 households. Combined cycle technology is regarded as the most technically advanced means of converting natural gas into electricity that is available today.
Where the existing plant at Huntly uses boiler steam to generate electricity, Unit 5 uses a gas turbine first and then uses what would otherwise be waste heat to generate more electricity using a steam turbine.
Factsheet: Thermal Energy
