Geothermal

= = toc =Geothermal Energy= = =

What is geothermal energy?
Geothermal energy (from Greek roots geo, meaning earth, and thermos, meaning heat) is the energy stored as heat in the earth.

Energy is brought to the surface by extracting hot water that is circulating amongst the sub surface rocks, or by pumping cold water into the hot rocks and returning the heated water to the surface, to drive steam turbines to produce electricity. Alternatively geothermal energy can be used directly for heating and cooling; in industry and agriculture, and domestically.





[|How it works]
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[|How it is used in Australia - Cooper Basin]
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Ergon Energy's hydrothermal power generation system at Birdsville

[|Geothermal Energy in Iceland]
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[|Cooling, Heating and Hot water] [small scale]
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SWOT Analysis

 * <  ||< **Strength** ||< **Weakness** ||< **Opportunity** ||< **Threats (risks)** ||
 * < Cost ||< * Geothermal power is cost effective, reliable, sustainable, and environmentally friendly ||< * Historically been limited to areas near tectonic plate boundaries
 * Drilling and exploration for deep resources is very expensive.
 * System efficiency does not materially affect operational costs as it would for plants that use fuel, but it does affect return on the capital used to build the plant.
 * Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. A typical well doublet (extraction and injection wells) in Nevada can support 4.5 megawatts (MW) and costs about $10 million to drill, with a 20% failure rate. ||< * Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, and interest rates. ||< Catastrophic failure ||
 * < Reliability ||< * Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor can be quite large – up to 96% has been demonstrated. ||< * In order to produce more energy than the pumps consume, electricity generation requires relatively hot fields and specialized heat cycles. ||< Which applications (in heating/electrical loading) does it fit well? ||< Fuel shortages/ sustainability issues ||
 * < Longevity ||< * The long-term sustainability of geothermal energy has been demonstrated at the Lardarello field in Italy since 1913, at the Wairakei field in New Zealand since 1958, and at The Geysers field in California since 1960. ||< * Extraction must still be monitored to avoid local depletion. ||< Might we see Tech improvements? ||< * Possible depletion of sources in certain areas ||
 * < Track Record ||< * Direct systems of any size are much simpler than electric generators and have lower maintenance costs per kW·h, but they must consume electricity to run pumps and compressors.
 * The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in online capacity since 2005. IGA projects growth to 18,500 MW by 2015, due to the projects presently under consideration, often in areas previously assumed to have little exploitable resource. ||< * Plant construction can adversely affect land stability. Subsidence has occurred in the Wairakei field in New Zealand and in Staufen im Breisgau, Germany. Enhanced geothermal systems can trigger earthquakes as part of hydraulic fracturing. The project in Basel, Switzerland was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection.
 * Even though geothermal power is globally sustainable, extraction must still be monitored to avoid local depletion. Over the course of decades, individual wells draw down local temperatures and water levels until a new equilibrium is reached with natural flows. The three oldest sites, at Larderello, Wairakei, and the Geysers have experienced reduced output because of local depletion. ||< * Geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels. ||< Price volatility ||
 * < Efficiency ||< * Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels.
 * Existing geothermal electric plants emit an average of 122 kilograms (269 lb) of CO2 per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust.
 * Geothermal has minimal land and freshwater requirements. Geothermal plants use 3.5 square kilometres (1.4 sq mi) per gigawatt of electrical production (not capacity) versus 32 square kilometres (12 sq mi) and 12 square kilometres (4.6 sq mi) for coal facilities and wind farms respectively. They use 20 litres (5.3 US gal) of freshwater per MW·h versus over 1,000 litres (260 US gal) per MW·h for nuclear, coal, or oil. ||< * The thermal efficiency of geothermal electric plants is low, around 10-23%, because geothermal fluids do not reach the high temperatures of steam from boilers
 * In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals such as mercury, arsenic, boron, and antimony. These chemicals precipitate as the water cools, and can cause environmental damage if released. ||< Job creation? ||<  ||
 * < Versatility ||< * Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation.
 * Geothermal power is highly scalable: from a rural village to an entire city. ||< * Direct geothermal heating systems contain pumps and compressors, which may consume energy from a polluting source. ||< Economic growth? ||<  ||
 * < Intermittency ||<  ||< * The thermal efficiency and profitability of electricity generation is particularly sensitive to temperature. ||< IP development? ||<   ||
 * < Fuel Scarcity ||< * Geothermal power requires no fuel (except for pumps) ||<  ||< Will deployment substantially drive E-curve? ||<   ||