This research paper focuses on the generation of electricity in Australia by the use of geothermal energy. The major areas focused on include the technologies used in the generation of electricity, advantages, problems, and future prospects of geothermal energy in Australia. The approach used to investigate the generation of electricity by Geothermal energy is through assessment of the present geothermal plants in the country and then evaluating their advantages and problems. The information regarding the geothermal plants can be acquired through personally accessing the reports and journals published by these power plants in form of annual reports.
Geothermal energy generates electricity by the use of molten core which is composed of rock of extreme high-temperature liquid referred to as magma. This geothermal heat circulates inside the rock or is transferred to the water reservoirs situated underground that is also involved in circulation beneath the earth’s crust. The high-temperatures aquifers inside the crust of the earth are surrounded by sand or rocks and are heated by the heat from the earth. Hot steam or water within the aquifers could reach temperatures more than 300oC. This heat is normally used for the electricity production. Australian continent has the high potential of these hot sedimentary and hot rock aquifer resources from the recorded temperature database during test drilling of 5700m deep holes around Australia.
There are three major technologies involve in the generation of electricity by the use of geothermal energy, these technologies include binary, steam, and flash power plants. The binary power plans denote 10% of the entire capacity of the world, while dry steam represents 26%, and the flash power plan represents 60% of the total capacity of the world. The major reason why the binary power plant accounts for a minute share of the world’s capacity is due to the minute power per unit production. It is the temperature and property of the geothermal vapour or fluid that governs which technology that should be applied to realize optimum electricity from the resources (Bahadori, 2013).
These technologies of electricity generation by the use of geothermal energy differ in numerous ways, despite the fact that the major electricity generation process is similar. In case the resource is hot-water, there is need to flash it to generate steam, whereas if the resource is dominated with vapour, it can directly be used in the generator-turbine (Barbier, 2009). The figure below shows the general process for the geothermal power plant:
Simplified processes for geothermal power plant (Bertani, 2009)
The geothermal fluid is generated from the reservoir through pumped flow, artesian, flow, or natural flow. Artesian flow occurs when the levels of water naturally rise to the level of ground as a result of hydraulic pressure. Natural flow takes place in wells produced through natural processes in the rock (DiPippo, 2012).
The binary power plants are the most current development and can accept the temperatures of the fluid as low as 57oC. The geothermal water that is hot moderately is delivered through a working fluid with low boiling point compared to water. This results in the flushing of working fluid to vaporize, which then rotates the turbines. It has been proved that the binary power plans are more appropriate technology for reservoirs with temperatures between 70 to 170 degrees. The binary power plants have the capability of operating at lower temperatures compared to other power plants have made them be more significant to the increase in the production of global geothermal energy (Dickson, 2009).
Binary power plant (Dickson, 2009, p. 187)
The major distinction between other power plants and this binary power plant is that instead of the generator being powered by the geothermal fluid, another fluid which may be secondary fluid or working fluid is subjected to a closed-loop cycle and produces electricity. The geothermal fluid is subjected to an exchange of heat with the secondary fluid resulting in evaporation and then pumped back to the reservoir. This denotes that the geothermal fluid does not come into interaction with the turbine or generator units. The technique of applying a working fluid makes this technology to be more complex compared to other power plant and hence this technology is more costly (Franco, 2011).
Nevertheless, this technology extends the lifetime of the equipment as a result of reduced wears of the turbine. The majorly used binary plants are those functioning with Kalina cycles or Organic Rankine Cycles. The Organic Rankine Cycles applies organic refrigerants as secondary fluid and not water steam used by conventional power plants. It is an appropriate technology for producing electricity from geothermal resources of low temperatures and hence majorly used in the majority of the EGS projects currently in Australia (Gupta, 2012).
There are two dissimilar categories of flash power plant, these include double and single flash power plant. All of these categories are applied when a mixture dominant with liquid is generated from the hydrothermal reservoir well. Flashing denotes that the geothermal fluid is subjected to the transitioning process from a liquid pressurized to a vapour mixture and liquid. This is attained by reducing the pressure beneath the saturation fluid pressure. The mixture of liquid vapour is divided into diverse stages in a flash container and the vapour is conveyed to a generator (Huenges, 2011).
Using a double flash plant can be used to achieve more steam at a lower pressure through installing an extra flash system. These plans will produce more power compared to a single-flash plant from a similar reservoir of geothermal power. Since reservoirs that are vapour dominant as more common compared to hydrothermal reservoirs, therefore, it is the technology of flash that is commonly compared to the technology of dry steam. Flash power plant uses geothermal reservoirs of water with temperatures more than 182oC (IBP, 2015).
This power plant in the least complicated technology of geothermal power plants since its uses hydrothermal resources that are vapour dominant by supplying the steam directly through the generator-turbine. This technology is not found normally since it needs a resource that generates dry steam despite being the simplest and efficient power plant. There may be present of water in these reservoirs, however, only steam is generated to the surface and no water is generated to the surface. The dry steam uses geothermal steam directly of 150oC then the steam is released to a condenser where it turns back into the liquid which is involved in cooling the water (Johnston, 2014).
After cooling, the water flows down the pipe that conducts the condensate back into deep wells where it can be heated again and generated again. Currently in Australia, there are no resources where this power plant can be implemented.
One of the major advantages of the geothermal energy is that it is eco-friendly in the sense that there is no form of combustion involved. Flash and binary geothermal plants emit also most close to zero greenhouse gas. The geothermal heat pumps used during cooling and heating buildings are ranked as one of the best efficient heating and cooling system currently due to their low energy requirements. Geothermal energy is also a renewable power source since it offers a reliable and constant source of green energy. There is no source of this energy that will disappear after being used. This energy can constantly be at disposal since the crust of the earth continuously replace the supply of water through rainfall and the interior of the earth is in a constant rate of heat production (Jonasson, 2014).
The establishment of geothermal energy has led to the development of the economy of rural areas which are generally characterized by unemployment. An average of 323 worker were involved in the construction of geothermal energy in Australia, and when these geothermal projects were in operation more than 57 new jobs were created in the areas of administration, engineering, operation, and maintenance. There are also significant savings in the utility bills when the geothermal system is used since it requires high upfront capital investments than other systems. There will be additional cash flow as a result of savings accrued from the utility bills (Manningtonb, 2010).
This system is characterized by high efficiency coupled with low maintenance since the system uses 25% electric power for heating and cooling. Besides geothermal energy systems possessing a long-lasting attribute, they are also friendly to the user and appropriate. There is also free hot water generation in the geothermal systems since modification of the system can be performed on the system to permit hot water delivery which can be stored for use for other purposes. Geothermal energy is also more flexible to bridge the gap caused by the irregular resources of renewable energy such as wind and solar. This is because the production of geothermal energy can easily be decreased or increased depending on the present demand so as to maintain the integrity of the national power grid and also the entire efficiency of the system of electricity generation in Australia. The last advantage of the geothermal energy is that there is no sound pollution since it has similar principles with the refrigerator or freezer (Marc Rosen, 2017).
One of the major challenges facing the geothermal energy system is that it is not widely spread energy source and the majority of states have not implemented the geothermal energy hence resulting in difficulties during the installation for bothering domestic and industrial use. The geothermal energy is also faced with potential emissions of greenhouse gas from the surface of the earth. These gases can migrate to these gases can be emitted to the surface and into the atmosphere and can be dangerous to the lives of plants and animals since they are related to emission of sulfur dioxide and silica. Also, the reservoirs may possess traces of lethal heavy metals such as boron, arsenic, as well as mercury (Tester, 2010).
The construction of geothermal power plans has also interfered with the surface stability in many regions in Australia where these stations are located. It has been proved that these plants may trigger earthquakes with a magnitude of 3.4 just like in Switzerland in 1997 where these plants triggered an earthquake. There have also been sustainability questions regarding the rate at which the reservoirs are currently being depleted. This is because of the high rate at which the fluid is being deplete compared to the rate at which it is being replaced. Additionally, despite being considered a renewable and sustainable energy, the chances are that some places may cool down after a given duration making it difficult for future geothermal energy harvesting. This may not be a concern in the case of residential geothermal cooling and heating since the energy is being utilized differently compared to the power plants (Marc Rosen, 2017).
The future prospect of geothermal energy in Australia is huge. The resources of geothermal energy in states such as Iceland and New Zealand are greatly used in the generation of electricity. These states have plenty of pressurized hot underground water as a result of geothermal activities near the surface. In Australia, the majority of the geothermal energy is extracted through water pumping from the surface through the rocks deep beneath the ground for heat absorption and then circulating this absorbed water back to the surface. This process is referred to as Enhanced Geothermal System (EGS). After approximately 10 years of inventor activity and promises, the Australian geothermal industry peaked in 2010 and to the end of 2013 which realized a cumulative investment of about $900 million (Marc Rosen, 2017).
Despite a successful test plant in central Australia, since then the government and investor sentiment regarding the future viability of the geothermal energy as a source of power generation seems to significantly wane. There is need of harnessing the geothermal energy is three major ways, the first one is the geothermal heat pump such as the one used in controlling the temperature of the Geosciences Australia structure is Canberra. This does not use a lot of geothermal energy since it takes advantage of the thermal mass of the earth to absorb heat during summer and then during winter releases it. The second one is the simple hot spring used for health seekers and tourism such as in Perth (Bertani, 2009).
The last is the generation of geothermal energy which is caused by lack of economic tap and not lack of heat. Just like in the United States, Australia has currently researched on the generation of electricity with enhanced geothermal systems (EGS). This involves the extraction of heat by the creation of the system of subsurface fracture in the hot essential rock to which that can be an addition of water through injection wells (Dickson, 2009).
Conclusion
This report is about the geothermal energy in Australia by majorly focusing on the technology of electricity generation using geothermal energy an also discussing the advantages, problems and future prospects of geothermal energy. There are three major technologies involve in the generation of electricity by the use of geothermal energy, these technologies include binary, steam, and flash power plants. The binary power plans denote 10% of the entire capacity of the world, while dry steam represents 26%, and the flash power plan represents 60% of the total capacity of the world.
Some of the advantages of geothermal energy include does not depend on weather conditions like solar energy, low maintenance cost, the energy can be used directly, non-pollution and environmentally friendly, an also it is a renewable source of energy. Some of the problems facing the geothermal energy include only a few sites have the geothermal energy potential, the total potential of generation is low, dangerous of volcanic eruptions, high installation cost, there is emission of poisonous and harmful gases, and also there is no guarantee n the quantity of energy that can be generated.
Enhanced geothermal energy systems are still considered to be a new technology in Australia and the potential areas for future developments are substantial. There is need of geothermal energy sector in Australia to additionally explore the mass flow technique used to improve the flow between geothermal wells since the potential improvements of these mass flow techniques would facilitate significantly in the creation EGS wells. The Australian government should also forecast of the future price of Large Scale Renewable Energy Certificates (LGC) since it largely affects the profitability of the geothermal power plants through its fluctuations. There is also need of exploring the potential areas of reusing geothermal wells such as old oil and gas wells in Australia can be used to establish the geothermal power systems.
References
Bahadori, A., 2013. A review of geothermal energy resources in Australia: Current status and prospects. Australia: Renewable and Sustainable Energy Reviews, Colorado, vol. 14, pp. 278-315.
Barbier, E., 2009. Geothermal energy technology and current status. Melbourne: Renewable and Sustainable Energy Reviews, vol. 5, pp. 169-173.
Bertani, R., 2009. Long-term projections of geothermal-electric development in the world. New York: GeoTHERM Congress.
Dickson, M., 2009. Geothermal Energy: Utilization and Technology. Perth: Routledge.
DiPippo, R., 2012. Geothermal Power Plants: Principles, Applications, Case Studies, and Environmental Impact. Melbourne: Butterworth-Heinemann.
Franco, A., 2011. Power production from a moderate temperature geothermal resource with regenerative Organic Rankine Cycles. Australia: Energy for Sustainable Development, vol. 13, pp. 358-417.
Gupta, H., 2012. Geothermal energy: An alternative resource for the 21st century. Colorado: Elsevier, vol. 9, pp. 158-214.
Huenges, E., 2011. Geothermal Energy Systems: Exploration, Development, and Utilization. Perth: John Wiley & Sons.
Huenges, E., 2011. Geothermal Energy Systems: Exploration, Development, and Utilization. Melbourne: John Wiley & Sons.
IBP, I., 2015. Australia Energy Policy, Laws and Regulations Handbook Volume 1 Strategic Information and Basic Laws. Perth: Lulu.com.
Johnston, W., 2014. Direct Geothermal Energy Demonstration Projects for Victoria, Australia. Victoria: IPENZ.
Jonasson, K., 2014. Western Australia’s Petroleum and Geothermal Energy Explorers Guide. West Australia: Western Australian Government – Department of Industry & Resources.
Mannington, W., 2010. Renewability of geothermal resources. Australia: Geothermics.
Marc Rosen, 2017. Geothermal Energy: Sustainable Heating and Cooling Using the Ground. Australia: John Wiley & Sons.
Rybach, L., 2011. The advance of geothermal heat pumps worldwide. Perth: IEA Heat Pump Center Newsletter.
Tester, J., 2010. Prospects for Universal Geothermal Energy from Heating Mining. Sydney: Science & Global Security, vol. 12, pp. 147-258.
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