Thursday, 10 November 2011

Renewable Energy

This special issue of four stamps illustrates the diversity of renewable energy production in Australia . The stamps issued on March 30, 2004 and designed by Sean Pethick .
Renewable energy is produced from sustainable sources such as the sun (solar), wind, water (hydro) and organic matter (biomass). Sustainable sources are those that are essentially inexhaustible or that are replenished quickly through natural processes.
Each of the renewable production methods featured on the stamps has been used in some form in Australia for some time. Yet renewable energy generation accounts for just nine per cent of our total power generation. More than 80 per cent of our energy comes from coal.

Energy production using sustainable sources generally is safer and cleaner than production using fossil fuels, such as coal, oil and natural gas. For example coal-fired power plants release large amounts of carbon dioxide into the atmosphere and contribute to greenhouse gas emissions.
Today it costs more to buy and use energy from renewable sources, but costs have fallen and will continue to fall as more efficient technologies are developed and the demand for renewable energy increases.
Even with just nine per cent of total energy generation coming from renewable sources, renewable energy production has the potential to save Australia thousands of tonnes of greenhouse gas emissions every year.
Solar energy makes direct use of the sun’s radiant heat. It is the least polluting and most inexhaustible energy source known, and its potential is only just beginning to be utilised.
In Australia today solar energy systems range from small household systems to large, grid-connected solar powered suburbs. It is most commonly used for domestic hot water.
Solar (photo-voltaic) cells are also used to convert solar energy into electrical energy.
These systems are silent, effective and relatively non-polluting, so they are suitable for urban areas. In Australia solar power has great potential to provide power to remote locations, such as outback telecommunications stations and lighthouses, and to remote communities not connected to the main electricity grid.
The stamp shows a Solar Systems CS500 dish, one of ten that makes up a solar station serving a remote Aboriginal community in central Australia. The dish tracks the sun from sunrise to sunset, capturing the sun’s energy, concentrating it and converting it to electricity.
The solar power station will reduce diesel consumption, which in turn can save the community money and reduce its greenhouse gas emissions.
Wind energy is one of the fastest growing technologies in the world. Global wind power capacity has quadrupled over the past five years.
Windmills have been used in Australia for nearly a century. The new way of harnessing wind energy is using ‘wind farms’ of turbines.
The wind turns the blades of the turbines. That mechanical energy is converted into electricity, which in turn is fed in to the local electricity network for distribution to homes. Wind generated electricity is produced without greenhouse gas emissions.
Wind farms already contribute power to electricity grids in Australia. Crookwell Wind Farm in New South Wales was the first grid connected wind farm in Australia.
There are about 16 wind farms operating today and at least as many again being planned. The stamp shows a wind turbine, typical of those erected in today’s wind farms.
Hydro power harnesses the energy produced by moving (often falling) water. The moving water turns the blades of a turbine and that mechanical energy is converted to electricity.
Unlike solar or wind energy, which depend on daylight or minimum wind speeds respectively, hydro schemes can produce power continuously, or water can be stored in dams and released when required to produce energy on demand.
About eight per cent of our electricity is already produced from hydro schemes. The Snowy Mountains Scheme is Australia’s largest and best known supplier of hydro electric power. It supplies ten per cent of New South Wales’ electricity needs as well as providing power for the evening rush hours of Sydney, Brisbane, Canberra, Melbourne and Adelaide.
Large hydro-electric projects require dams, which are expensive. Dams also have a large impact on the environment because they change the fl ow of rivers and flood large areas of land.
So there is increasing interest in alternative, smaller hydro schemes, such as pumped storage systems, and ‘run of river’ systems.
A number of micro-hydro units are in use for domestic power supplies in remote areas.
The stamp shows water being released from a dam in the Snowy Mountains Scheme.
Biomass is organic matter that can be used to produce electricity and supply heat and fuel. Biomass comes in different forms such as bagasse (the waste plant fibre left after the juice is removed from sugarcane); greenwaste (the tree clippings from gardens, parks or plantations); food processing waste (such as nut shells and grain husks, fruit and vegetable peel and other waste from canneries); and vegetable oils.
Although carbon dioxide is released when biomass is burned, the continued growth of biomass takes an equivalent amount of carbon dioxide from the atmosphere. So unlike burning coal, using biomass to produce energy does not add to overall carbon dioxide levels in the atmosphere. Biomass also has negligible levels of pollutants.
Another advantage of using biomass for energy production, is that it often recycles the waste products from other processes, such as sawmilling or food processing.
For example bagasse is used to fire boilers in sugar mills. The high-pressure steam produced by the boilers is used to turn turbine blades. The mechanical energy of the turning blades can be converted to electricity.
Much of the steam and electricity from bagasse is used directly by the mill in the sugar making process. The excess electricity is sold on the state’s electricity grid.
Sugar mills have been exporting power to electricity grids to varying extents for decades.
The stamp depicts bagasse use, with a sugar cane field in the foreground and a sugar mill in the background.


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