Australia's low emission energy future
Key text
This topic is sponsored by Queensland Resources Council.
The Australian Government wants to reduce greenhouse gas emissions by at least 5 per cent of 2000 levels (and possibly up to 25 per cent) by the year 2020. But with a growing population, increasing energy requirements, and a past reliance on cheap energy sources how could this be achieved?
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You will get more from this topic if you have mastered the basics of energy – these links will take you to an annotated list of sites with helpful background information. |
Like many countries, Australia is facing a dilemma in meeting its commitment to control greenhouse gas emissions beyond the Kyoto protocol. The Australian population is expected to swell from the present figure of 21 million to around 35 million by 2056, and demand for energy is surging with it. So, with a growing demand for energy, how are we going to achieve the goal of a low emission, cost-effective energy future?
Well, there are four main strategies Australia could adopt, which involve:
- continuing to use fossil fuels, while developing the use of low emission fossil fuel technologies;
- encouraging the use of low-emission renewable sources of energy such as solar, wind and geothermal power;
- improving the energy efficiency of Australian households and businesses and managing energy demand (Box 1: Reducing emissions by increasing energy efficiency) and;
- placing a price on carbon through an emissions trading scheme (ETS).
The introduction of an ETS such as the one in place in the European Union places a cap on greenhouse gas emissions, with companies that emit significant amounts of greenhouse gases having to buy permits to do so (Box 2: How an emissions trading scheme works).
Reducing emissions from fossil fuels
A movie and interactive resource on
low emission energy. The movie includes
a good introduction to low emission fossil
fuel technologies.
(Queensland Resources Council, Australia)
Around ninety-four per cent of Australia’s energy requirements come from burning fossil fuels such as coal, oil and natural gas (Box 3: Electricity generation).
Although burning fossil fuels releases greenhouses gases (mainly carbon dioxide or CO2) Australia is likely to continue relying on them for energy, at least in some capacity, because of their availability and relatively low cost.
Cleaner coal?
Developing low emission fossil fuel technologies (sometimes referred to as 'clean coal' technologies) is seen as one way to lower emissions, while still using our abundant fossil fuel resources. Several methods are being investigated or trialled around Australia, with the technology still developing and not yet competitive with conventional power generation.
Some of the technologies being investigated for coal in Australia include:
Integrated gasification combined cycle (IGCC)
The integrated gasification combined cycle is a two-step process designed to reduce CO2 emissions from a coal-fired power station.
The first stage involves turning coal into a gas, in what’s called coal gasification. This involves feeding the coal into a heated, pressurised container with steam and oxygen. The resulting synthesis gas, or ‘syngas’ mixture consists of mainly hydrogen (H2) and carbon monoxide (CO). This gas mixture is reacted with additional water to convert it into a mixture of additional hydrogen and carbon dioxide (CO2). In a process known as pre-combustion carbon capture, the CO2 can be removed, compressed to a liquid and stored, usually deep underground.
The second stage of the process involves burning the remaining hydrogen in a gas turbine that turns a generator to produce electricity. The resulting hot exhaust (mainly steam) is then used to make more steam, that then turns a steam turbine producing more electricity. The dual use of a gas and steam turbine, gives the process its 'combined cycle' name.
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Integrated gasification combined cycle (IGCC) with carbon capture and storage
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The basic IGCC process without carbon capture and storage (CCS) is more efficient and produces fewer carbon emissions than conventional coal-fired power stations. With the additional reaction to produce CO2 and then remove and store it, the efficiency of the process reduces. However, it can reduce CO2 emissions to the atmosphere by up to 90 per cent. An added advantage of the IGCC/CCS method is that it produces hydrogen, which can be used to provide low emission energy in stationary fuel cells or as a fuel for hydrogen powered vehicles.
IGCC has yet to be proven on a commercial scale in Australia and costs will initially be higher compared to conventional coal-fired power stations. The introduction of a cost on carbon emissions, by an ETS would help to make the technology more competitive.
Underground coal gasification
Underground coal gasification (UCG) is another way of turning coal into a gas, but this time it’s done underground.
A bore hole is drilled down into the coal seam and by feeding oxygen or air down to the coal, it is ignited and burned underground. The resulting syngas is then piped to the surface through another bore hole where it is used to produce electricity using a combined cycle gas power station.
It is claimed that UCG extracts a lot of energy for a relatively small footprint (compared to coal and coal seam gas), but its environmental impact on groundwater and the surrounding environment is being investigated. The process does produce CO2 that will need to be captured and stored appropriately to qualify as a low emission technology.
 The underground coal gasification process burns coal underground to produce syngas. (Image: courtesy of Linc Energy Ltd) |
Oxyfuel combustion
In conventional coal-fired power stations, coal is burned in air. With oxyfuel combustion, instead of using air, the coal is burned in oxygen and recycled flue gas. This produces a flue gas that is mainly water and CO2. The water is removed by cooling the flue gas, and the remaining CO2 is then compressed into a liquid which can be stored eg, underground (see Carbon capture and storage below). This technology is being tested at the Callide oxyfuel project at Biloela in central Queensland.
The advantage of this method is that it can be fitted to existing coal-fired power stations. By producing flue gas that has a high concentration of CO2, it is easier to capture the CO2. As with IGCC, oxyfuel combustion is still being developed for commercial scale operations.
Reducing emissions with gas
Both natural gas and coal seam gas are mostly methane (a greenhouse gas, CH4) and strangely enough, can play a key role in generating electricity with fewer greenhouse gas emissions. A power station fired by gas produces about half the greenhouse gas emissions of a normal coal-fired power station, because methane contains less carbon per unit of energy than coal. Australia is well placed to use gas technology having large gas reserves eg, in the Carnarvon Basin in Western Australia (natural gas) and the Surat and Bowen basins (coal seam methane) in Queensland.
Low-emission gas technologies being investigated in Australia include:
Coal seam methane gas (CSG) is found associated with underground coal deposits. Traditionally, coal mines have vented the gas into the atmosphere because it poses a health and safety risk during mining. But methane is a powerful greenhouse gas in the atmosphere.
The methane in some underground coal deposits is now being collected and used to generate electricity by burning it in gas turbines. There is particular potential for coal seam gas as a source of energy in New South Wales and Queensland with nearly six per cent of Queensland's energy needs coming from this source. The Dawson mine in Queensland, for example, is one of the world’s largest producers of coal mine methane power.
To extract coal seam gas, water is pumped up from the coal seam to lower the pressure and encourage the gas to flow to the surface. The environmental impact of the large volumes of water with varying salinity levels that are produced, as well as the effect of operations on groundwater, need to be considered when designing CSG plants.
Combined cycle gas turbine (CCGT)
As with IGCC, combined cycle gas-fired power stations burn gas in a turbine to produce electricity, then use the waste heat to generate steam that turns a steam turbine to generate more electricity. These power stations, such as Pelican Point power station just outside Adelaide, operate more efficiently than older coal-fired stations, and with fewer greenhouse gas emissions.
dioxide capture
(©CO2CRC 2008)
(Click on image for a
larger version)
The Australian Government and industry are supporting the development of commercial-sized carbon capture and storage (CCS) projects, where CO2 emissions from burning fossil fuels are captured and stored deep underground. The CO2 can be collected at either the pre-combustion stage (as in IGCC) or the post-combustion stage.
The post-combustion capture process involves burning fossil fuels in a power station and then collecting the CO2 from the flue gases. The CO2 can then be liquefied, transported and stored underground (geosequestration). Australia has established a demonstration geosequestration plant near Warrnambool, in south-west Victoria. The viability of CCS technology on a commercial scale still remains to be proven.
Renewable energy sources
Renewable energy sources are those that don’t run out or are quickly replenished such as solar, wind, geothermal and ocean energy.
Renewable energy sources currently account for only 5 per cent of Australia’s total electricity, but the government has legislated to increase this to 20 per cent by 2020. Emissions from renewables are minimal compared to fossil fuels, but their uptake has been limited by issues with cost, variability, location and the status of the technology.
 Greenhouse gas emissions and cost of producing electricity using selected technologies. (Sources: National Academy of Sciences 2009; CSIRO 2006. Life-cycle emissions, approximate only, varies widely depending on technology and site). |
Solar
Although we don’t yet make the most of it, Australia receives more sunshine that almost any other country. Under the government’s $1.6 billion Solar Flagships Program, four large solar power stations (with a total capacity of an average coal-fired power station) are due to be constructed by 2015 to demonstrate the feasibility of solar technology.
Solar energy can be generated from solar thermal energy or by photovoltaic cells. Solar thermal systems use the sun’s energy to heat a liquid like water or oil. These can be small rooftop systems or, on a larger scale, collections of mirrors that focus the Sun’s rays to heat water to steam, to generate electricity. Photovoltaic solar energy involves flat panels that turn sunlight directly into electricity.
The main disadvantages of solar energy are cost and variability of supply. Obviously, the sun doesn't shine at night and the radiation we receive varies throughout the day and with cloud cover. The development of technology to store the heat from solar thermal systems, then use it to generate electricity at night, may make the supply of energy from these systems less variable.
Wind power
Wind power, where wind drives giant turbines to generate electricity with minimal greenhouse gas emissions, is a rapidly growing form of energy production in Australia. Most wind power sites are currently in South Australia, Victoria and Western Australia.
Although one of the more promising renewable technologies, issues with wind power include aesthetics of the turbines, bird strikes, noise and variability of supply with wind conditions.
Geothermal energy
Geothermal hot rock energy is created from the hot granite rocks several kilometres below the Earth’s surface. Water circulated through the fractured rocks, is heated and then pumped back to the surface to generate electricity with few emissions.
Although Australia has enormous geothermal resources and a growing interest in using them, the remote location of most of the resources can be an issue, and the technology is still developing. There is currently only one small, operating geothermal power station in Australia, at Birdsville in Queensland.
Bioenergy
Bioenergy is a renewable form of low-emission energy made from biomass (organic or vegetation matter). Probably the best known form is bagasse, which is crushed sugar cane waste. Bagasse has been used as a fuel to generate electricity for sugar mills in Queensland for more than 100 years. However, biomass can also come from other crops and waste materials. Some refuse stations capture methane gas produced from decomposing rubbish; the gas can then be burned to produce energy. Competition from biomass crops for farming land and water resources has prompted research into alternative sources of biomass, such as algae.
Ocean power
Another form of energy being developed is ocean power, which can either use rising and falling tides, or the surging power of waves, to turn turbines to make electricity.
Despite having a long coastline and some of the best wave energy in the world, ocean power is a largely untapped energy source in Australia, with significant technical challenges. The location, high cost and amount of energy generated has attracted limited investment to date. There is one wave-powered pilot plant operated by Oceanlinx at Port Kembla in NSW, while other ocean-powered generators are being developed in Western Australia, Victoria and Queensland.
Hydroelectricity
Hydroelectricity schemes, which use flowing water to turn turbines to generate electricity, are an established technology currently providing 17 per cent of Australia’s renewable energy supplies. There are large hydroelectric schemes operating in Tasmania, the Snowy Mountains in New South Wales, north-east Victoria, Queensland and the Ord River in Western Australia.
Although hydroelectricity is a relatively inexpensive, low-emission form of energy, schemes across Australia have been affected by drought conditions, and there can be concerns regarding the damming of rivers to supply sufficient quantities of water. Because of Australia’s relatively flat landscape and uncertain water supply there is little scope for the development of additional hydroelectric generation.
Other low-emission energy sources
Hydrogen
Researchers in Australia and many other countries are looking to hydrogen to replace fossil fuels for powering turbines, fuel cells and vehicle engines.
Hydrogen is the most abundant element on Earth but is mostly combined with other elements, such as oxygen, in the form of water. It is an energy carrier, rather than a primary energy source such as oil. So it has to be produced from other sources. Most hydrogen is currently produced from fossil fuels, principally natural gas. Hydrogen can also be produced from renewable energy sources but these aren't cost-competitive. Most of the hydrogen produced in Australia is used in the petrochemical and fertilizer industries, not for power generation.
Uranium
Uranium is a low-emission source of energy that has not been used for energy purposes in Australia, mostly due to the abundant fossil fuel reserves, safety concerns and the challenges of storing waste for long periods. However, the mining of uranium for export is well-developed. Australia has some 40 per cent of the world’s easily recoverable uranium resources and supplies about 19 per cent of the international market.
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Putting it all together
With a growing demand for energy, there is no simple way of achieving Australia's goal of reducing carbon pollution by up to 25 per cent of 2000 levels by 2020. Like other countries, we are likely to continue using coal for energy, to some degree, into the future. The development of low emission fossil fuel technologies, increasing the use of gas and alternative energy sources, and adopting more energy efficiency measures, are all expected to play an important role in reducing Australia’s emissions from energy.
Boxes
1. Reducing emissions by increasing energy efficiency
2. How an emissions trading scheme works
3. Electricity generation
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Posted February
2010, edited August 2012.