What is co-generation? Co-generation, an efficient method of generating energy,
involves producing electricity at the same time as creating heat and steam for ...
CO-GENERATION What is co-generation? WHAT IS CO-GENERATION? Co-generation, an efficient method of Co-generation is the of electricity in generating energy,production involves producing combination with industrial process. electricity at theanother same time as creating heat Co-generation plants are often thermal and steam for industrial purposes, such as generators installed in industries drying timber in kilns or drying that milk produce powder. or require heat. In effect, the heat is used twice – In large factories, wood waste, gas or once to generate electricity and once forcoal another is usedresulting to generate for the factory. purpose, in aelectricity very efficient process Surplus electricity can be exported to the overall. National Grid. Co-generation can produce both Zealand, electricityco-generation and hot steamplants for factory use. In New are found in the wood processing, dairy and steel indusWhat types of co-generation are there? tries. In New Zealand, the main types of WHAT TYPES OF CO-GENERATION ARE THERE? co-generation are open-cycle gas Co-generation can work in one of two turbines andsystems steam turbines. ways. How is electricity generated through co-generation?
THE CARTER HOLT HARVEY PULP AND PAPER MILL IN KINLEITH IS A GOOD EXAMPLE OF A CO-GENERATION SCHEME. SOURCE: GENESIS ENERGY
Bottoming cycle at a paper mill (open-cycle Co-generation Heat produced in the form of high-pressure gasisturbine) steam and used in the industrial process. Co-generation uses heat from The leftover heat is thenthe recovered andanused to open-cycle gasdrives turbine in a boiler, which make steam that a turbine and generator. produces steam. This steam is used in two ways: Topping cycle This works the other way around. First, electricity is • to dry fres hly milled pa per in the fa ctory generated, usually through an open-cycle gas • to turn a s tea m turbine turbine, then the waste heat is used to produce The steam turbine drives a generator. steam for industrial purposes. The generator then produces electricity. The power paper stations mill usesnow the use electricity to efficient run Many the more its business and the rest to thespeaking, combined-cycle gasexports turbines. Technically National Grid for to themselves use. combined-cycle gaseveryone turbines are examples of co-generation. First, gas is ignited. Co-generation at a dairy factory It expands as it burns in a gas turbine connected (steam turbine) to an electrical generator, then the leftover heat from thisofprocess is used to make Some the heat produced by steam, a dairywhich factory drives a steam turbine secondThe generator. is used to turn waterand intoasteam. steam The second generator is not as efficient as the first, turns a turbine, driving a generator. The but still produces what could have generator then electricity produces from electricity. The dairy been waste heat. factory uses the electricity to run its business and exports the rest to the National Grid for WHAT ARE THE ADVANTAGES OF everyone to use. CO-GENERATION? What are the advantages of co-generation? Co-generation makes use of excess heat, which helps to improve the overall the Co-generation makes use efficiency of excess of heat, process. canoverall save businesses which Co-generation helps to improve efficiency of money, as they can generate their own electricity the generator. In comparison to other ways and steam supply at the same time. They can of generating energy, it’s more efficient, as it sometimes also and sell electricity to the national grid, uses the heat energy generated by fossil which New Zealand.can save fuelsprovides or woodpower waste.to Co-generation businesses money as they’re generating their
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own electricity and steam supply. What are disadvantages WHAT AREthe THE DISADVANTAGES OF of co-generation? CO-GENERATION? Even though co-generation produces electricity Even though co-generation uses electricity efficiently on site, it burns non-renewable generated efficiently in the business, it can sources that produce carbon dioxide emissions. burn non-renewable sources which produce carbon dioxide emissions. HOW CAN CO-GENERATION BE USED IN NEW How ZEALAND? is co-generation used in New Zealand? Although co-generation is a relatively new Co-generation is a relatively new technology technology in New Zealand, several of our in New Zealand. It has the potential to be primary industries are being made more used throughout the country due to our efficient by installing co-generation plants. primary industries, such as dairy, paper, For example, a timber mill or paper mill might and steel production. burn waste wood scraps to produce heat. This might used to driveschemes a steam operate turbine and A few be co-generation in generate electricity for the mill. The excess New Zealand today. The Fonterra Plant in heat from the turbine be further used, such as Te Awamutu andmight the Carter Holt Harvey for drying purposes, any electricity Pulp and Paper Mill while in Kinleith are two that is not neededCombined, could be fed into co-generation the national grid. examples. these This would extremely efficient use of plants havebea an capacity of 67MW, enough what mayto have been unwanted waste. capacity power 60,000 homes.
ACTIVITY Small group that brainstorming activity. For industries require heat for drying, such as• the Thidairy nk of industry a t lea s t owhen ne otdrying her busmilk inespowder, s tha t it can be economical to produce their own could use co-generation. Look at the electricity bywaste running small generating plant, types of theabusiness is creating andand thenhow to use waste heatbe from the thethe waste could used to turbine for theenergy. drying process. generate • Do you think co- ge ne ra tion is a n ACTIVITY environmentally-friendly type of Small groupgeneration? brainstorming activity energy Explain. • Dis cus s whether s ma ll or medium s ized Think of at least one other business that could enterprises could pool their resources use co-generation. Look at the types of waste and use co-generation as a method of the business is creating and how the waste generating energy. could be used to generate energy. Do you think co-generation is an environmentally-friendly type of energy generation? Explain. Discuss whether small- or medium-sized enterprises could pool their resources and use co-generation as a method of generating energy.
The steel industry uses huge amounts of energy in its iron melters. In the steel-making process, there is a lot of waste gas from the furnaces. In a co-generation plant, this waste gas would be recovered and burnt, and the heat used to produce steam to drive a steam turbine and generator.
SUPPORTING RESOURCES - Energy Efficiency and Conservation Authority: www.eeca.govt.nz - Ministry of Economic Development: www.med.govt.nz - Genesis Energy: www.genesisenergy.co.nz
