THERMAL WHAT IS THERMAL GENERATION? What is thermal generation? Thermal generation is the process of generating electricity heat. Heat is atoform energy. Thermalfrom generation refers the of process Heat energy that is turned into electricity can be of generating electricity from heat. There made in many ways. It can fuels: be produced by are four thermal energy coal, natural burning fuelswaste such as coal, oil, gas or wood. gas, wood and geo-thermal. StrictlyIt can also be takennuclear from steam from a geothermal speaking, power is also thermal field, or created by nuclear reactions. energy fuel, but it is set aside in a class of its own because of it’s unique traits. In this factsheet you will learn about the burning ofFossil fossil fuels, fuels (coal, gas),and wood such oil, as gas coal,(biomass) were and geothermal energy. For more information created millions of years ago from layers about nuclear power, thematter. ‘Nuclear Energy’ factsheet. of animal andsee plant When coalsuch is burnt to produce heat,were this heat Fossil fuels, as gas, oil and coal, can bemillions used toofcreate Theanimal steamand created yearssteam. ago from drives the steam turbine, which isand connected plant matter that was compressed compacted insideThe layers of rock. to a generator. energy produced by the generator is passed through a transformer When coalNational is burnt Grid to produce heat energy, this into the transmission line which heat energy can be used to create steam. The delivers electricity throughout New Zealand. steam drives the steam turbine, which is Natural gas provide energy through the connected to can a generator. The energy produced of burning it for heating cooking. byprocess the generator is passed throughand a transformer It can be used totransmission fuel an electricity into thealso National Grid line. turbine. This is the system that delivers electricity to all of Wood waste (bio-mass) comes from wood New Zealand. processing plants and other related industries. Often the wood waste is disposed of, but in Biomass means a fuel that is made from living someThe situations it can be burned order things. most common exampleinof this to is produce heat energy. Heat energy can make wood waste, which comes from wood processing steam. Steam drives a steam to plants and related industries; forturbine example, pulp and paper mills. Often the wood waste is generate power. disposed of, but in some situations it can be Three to types of power arewhich used can to be burned produce heatplants energy, generate powerways fromtogeo-thermal energy: used in different generate electrical dry steam, flash and binary. Dry steam energy. plants take steam out of fractures in the Geothermal energy is the heat that flows continuously from the hot interior of the Earth to the cooler surface. most places the ground and use it to In directly drive ain turbine world, there is not enough of this heat to use that spins a generator. for generating electricity. New Zealand is one of just a few countries in the world that have geothermal fields where hot rocks are close enough to the surface to be useful. Wells are drilled deep into the ground and a mixture of hot water and steam is taken out at high pressure. This steam is separated and piped to the power station, where it is used to drive a turbine and generator in the same way as at other power stations. The water is usually put back into the ground, so that the geothermal reservoir isn’t depleted. HUNTLY POWER STATION IN THE NORTH ISLAND SUPPLYS UP TO 20% OF NEW ZEALAND’S ELECTRICITY. SOURCE: GENESIS ENERGY HOW DO STEAM AND GAS TURBINES WORK? In New Zealand, three types of turbines are How is electricity generated from thermal used to drive the electrical generators of energystations: fuels? power In New Zealand, three types of turbines Conventional steam generate heat fromturbine natural gas: The fuel is burnt in a boiler to heat water into Conventional Steam Turbine steam under high pressure. A conventional steam turbine uses the pressure of the Gas is burnt in a boiler toaheat water into expanding steam to turn turbine. The steam. A conventional steam uses turbine drives a generator. Theturbine whole process high pressure steam to a turbine. The converts heat energy to turn rotational kinetic turbinewhich drivesisa then generator whichinto converts energy, converted electrical kinetic energy into electrical energy. energy. Open Cycle Gas Turbine Open-cycle gas turbine An Anopen-cycle open cyclegas gasturbine turbineisisvery verysimilar similarto toa jet engine onon anan aircraft and is the most basic a jet engine aircraft and is the most thermal energy turbine. Air is passed through basic thermal energy turbine. Air is passed athrough compressor and is then mixed with fuel gas a compressor and is then mixed in a combustion chamber. It is then burnt and This work is copyright. The copying, adapting or issuing of this work to the public on a non-profit basis is welcome. No other use of this work is permitted without the prior consent of the copyright holder. From ElectroCity www.electrocity.co.nz © Genesis Energy 2010. the hot expanding gases create thrust that withthe fuelgas gasturbine. in a combustion turns The shaft chamber. of the gasIt is then burnt and the hot create thrust turbine is connected to agases generator which that turnselectricity. the gas turbine shaft. The gas generates turbine shaft is connected to a generator Combined-cycle gas turbine which generates electricity. Combined-cycle gas turbines first combust the Combined Cycle Gas Turbine gas in a gas turbine, which produces electricity as above. The exhaust heat is then passed Combined cycle gas turbines combust the through a boiler to create steam which turns a gas and then pass the exhaust heat through steam turbine. The steam turbine produces a boiler to createand steam. The steamthe turns further electricity, so improves overall a steam turbine, which generates power. efficiency of the operation. Both the gas turbine and the steam turbine are connected to the generator. WHAT ARE THE ADVANTAGES OF THERMAL ENERGY? What arebenefit the advantages The main of thermal energy is that it can of thermal energy? provide continuous, reliable energy that is not dependent on the weather. The main benefit of thermal energy is that it can provide continuous, reliable energy that Coal is not on the Coal hasdependent been a useful fuelweather. for generating electricity for many decades because it is Coal relatively cheap and available. Coal is in plentiful supply worldwide which fuel generally makes its Coal has been a useful for generating price and availability Zealand electricity for many reliable. decadesNew because it is has abundant reserves of coal: near Huntly in relatively cheap and available. Coal is inthe North Island, and on the West Coast and in plentiful supply worldwide which generally Southland in the South Island. makes its price and availability reliable. New Zealand Natural gas has abundant reserves of coal. Efficient gas turbines produce a Naturalcombined-cycle Gas lot more electricity and less pollution than coal, meaning put out much carbon dioxide Efficient they combined cycle gasless turbines produce into the atmosphere for the same output of a lot more electricity and burn cleaner than electrical energy.they emit much less carbon coal, meaning dioxide (CO2) into the atmosphere. Wood waste Wood is generally sourced from a pulp Woodwaste Waste and paper mill which needs electricity and WoodTherefore waste is athe renewable fuel. steam. waste ofsource the millofcan be Wood waste is steam generally from used to provide andsourced energy for theamill. This reduces transportation New Zealand pulp and paper mill whichcost. needs electricity has huge forests of exotic trees. and steam. Therefore the(non-native) waste of the mill The processing of these trees into paper or can be usedresults to provide steam and energy milled timber in a large amount of bark forwood itself.waste, This reduces transportation and which can be burnt in acost. boiler Zealand hasmanufacturing vast forests of and/or exotic toNew create steam for electricity generation. Thisprocessing is a good example (non-native) trees. The of theseof co-generation, and is discussed further in the trees into paper or milled timber, results in separate factsheet on co-generation. a large amount of bark and wood waste, which can be burnt in a boiler to create steam Geothermal for manufacturing or electricity generation. Geothermal energy is the only renewable thermal energy available in the world. Using Geo-thermal geothermal energy is a cleaner, greener way to Geo-thermal energy is the only renewable produce thermal energy, compared to using fossil fuels,energy and is not dependent the weather thermal available in the on world. Using orgeo-thermal mining. energy is a cleaner, greener way to produce thermal energy, compared WHAT AREfuels, THE DISADVANTAGES OF THERMAL to fossil and is not dependent on the ENERGY? weather or mining. All thermal power stations produce steam which once used drive the turbine is still too hot to What areto the disadvantages discharge directly. Resource consents stipulate of thermal energy? how waste steam must be cooled before it can beCoal discharged to the environment. Coaldisadvantages is a non-renewable resource and Other are specific to particular is only available in a few select areas fuels. of New Zealand. Burning coal creates Coal carbon dioxide emissions which contribute Coal is a non-renewable to greenhouse gases. resource and is only available in a few areas of New Zealand. Burning Natural Gas coal creates carbon dioxide emissions which contribute to greenhouse gases. Natural Gas is a non-renewable resource and isgas only produced in the Taranaki region Natural whichgas limits supply. Natural gas, once Natural is athe non-renewable resource and, in burned, also is creates carbon dioxide New Zealand, only produced in theemissions. Taranaki region. Natural gas, once burned, also creates Wooddioxide Waste emissions. carbon A renewable resource, wood waste creates Wood waste carbon dioxide emissions once burned A renewable resource, wood waste creates although this is largely offset by growing carbon dioxide emissions once burned, although new trees. Supply is limited dependent this is largely offset by growingand new trees. Howon what’s available. ever, the supply is limited and dependent on what is available. Geothermal Geo-thermal Even though geothermal energy is technically renewable, this is dependent on the careful Even though geo-thermal energy is renewable, management of geothermal fields, for example itsre-injection lifetime is limited, so we to be careful by of water intoneed the underground with howrocks. we manage geo-thermal reservoir It is alsoour relatively expensive to resource. It’s also expensive to build awith large build a geo-thermal plant. Compared fossil fuel-burning powergenerate stations, geo-thermal plantthermal and it doesn’t geothermal stations have relatively smaller a lot of energy compared to other sources. generating capacities. How is thermal energy used in New IS Zealand? HOW THERMAL ENERGY USED IN NEW ZEALAND? Thermalenergy energyplays playsaakey key role role in in supplying supplying Thermal NewZealand’s Zealand’s electricity. electricity. Huntly Power Station New is the country’s largest power station Genesis Energy’s Station is the generating up toHuntly 20% ofPower New Zealand’s country’s power station. It has six electricitylargest requirements. separate generating units: four conventional Huntly Power Station five separate boiler and turbine unitshas that can burn coal units (four turbines which orgenerating gas and that each generate 250 MW each of power, one gas-fired turbine generating generate 250MW of power annually and 48 MW andred a 385 MW combined gas one gas-fi turbine generatingcycle 48MW turbine (a –250 MW of gas turbine annually). plus a 135 MW annually a total 1048MW steam turbine) – a total capacity of 1433 MW. A new 385MW combined cycle gas turbine Huntly is capable of producing nearly 13 TWhr is nearing completion at Huntly. This new (13 million MWhr) of energy each year – about power station will reduce the amount of 20% of New Zealand’s electricity requirements. coal burnt at Huntly and will reduce carbon dioxide emissions as well. Other fossil-fuel burning power stations are located in Auckland, Taranaki and Hawke’s Bay. New Zealand is a pioneer in the use of geothermal energy. Wairakei is the oldest operational geothermal power station in the world. New Zealand’s other geothermal power stations are all in the Taupo Volcanic Zone and the Northland geothermal field. In total they account for 635 MW or nearly ACTIVITIES 7% of our generating capacity. ACTIVITY ONE ACTIVITIES Research project: What are carbon-dioxide ACTIVITY ONE emissions and why are they bad for the Research project: environment? What are carbon-dioxide emissions and why are they bad for the ACTIVITY TWO environment? Divide the class into seven groups. ACTIVITY TWO Assignthe each group of the following Divide class intoone seven groups. Assign energy sources: each group one of the following energy sources: • Co-generation • WindCo-generation • Hydro Wind • Thermal Hydro Thermal • Nuclear Nuclear • Ocean • SolarOcean Solar Each group presents a case for why their Each group presents casetofor their energy source is the abest thewhy class. energy source is the best to the class. SUPPORTING RESOURCES - New Zea la nd Geotherma l As s ocia tion: www. nzgeotherma l. org. nz Energy Efficiency a nd Cons erva tion Authority: www. eeca . govt. nz Minis try of Economic Development: www. med. govt. nz Wikipedia: http://en.wikipedia.org/wiki/Electricity_sector_in_New_Zealand