geothermal energy
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Description of geothermal energy use
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geothermal energy
- 2. Geothermal Geo the Earth Thermal Heat Geothermal energy is the natural heat of the Earth. It is a renewable energy source for electricity generation
- 3. Why Geothermal? • Our planet is a huge source of energy. In fact 99.9 per cent of the planet is at a temperature greater than 100°C; so geothermal energy is a significant renewable resource(c). • Geothermal energy has the advantage that it can be available 24/7 all year round providing constant power with minimal visual and environmental impacts that other low carbon form of energy production cannot.
- 6. Geothermal reservoirs • Geyser • Boiling mud pot • Volcano • Hot springs
- 9. Energy Sourse used in 24 countries Geothermal reservoirs can reach temperatures of 700oF.
- 11. History • Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904 in Larderello, Italy. It successfully lit four light bulbs. • Later, in 1911, the world's first commercial geothermal power plant was built there. • Italy was the world's only industrial producer of geothermal electricity until 1958. • In 1958, New Zealand became the second major industrial producer of geothermal electricity. • In 1960, Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States at The Geysers in California. • The binary cycle power plant was first demonstrated in 1967 in Russia and later introduced to the USA in 1981. • Worldwide, 11,400 megawatts (MW) of geothermal power is online in 24 countries in 2012.
- 13. Direct use of Geothermal Energy • Hot springs, used as spas. • Heating water at fish farms. • Provide heat for buildings. • Raising plants in greenhouses, drying crops. • Provides heat to industrial processes.
- 14. Resources • Electricity generation requires high temperature resources that can only come from deep underground. • The heat must be carried to the surface by fluid circulation, either through: Magma conduits Hot springs Hydrothermal circulation Oil wells Drilled water wells or a combination of these. • Away from tectonic plate boundaries the geothermal gradient is 25- 30°C per km of depth in most of the world, and wells would have to be several kilometers deep to permit electricity generation. • The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries
- 17. Dry Steam Plant
- 22. Cost Direct use of geothermal energy is absolutely cheaper than other energy sources. Cost of electricity generation depends upon certain factors: • Temperature and depth of resource • Type of resource (steam, liquid, mix) • Available volume of resource • Size and technology of plant The initial investment is high. But after certain time period, the cost of electricity becomes comparable to other resources of energy. US $0.05 to $0.08 per kWh. Once the capital cost is recovered, the price can decrease to below US $0.05 per kWh.
- 23. Advantages • Available all the year around • Does not involve any combustion of fuel • Independent of weather • Clean Resource – Very little emissions or overall environmental impact • Economically Sound Alternative – The fuel is free, rate / KWh likely to be competitive
- 24. Disadvantages • Not widespread source of energy • High installation costs • Can run out of steam • May release harmful gases • Transportation • Earthquakes
Editor's Notes
- Heat flows outward from Earth's interior. The crust insulates us from Earth's interior heat. The mantle is semi-molten, the outer core is liquid and the inner core is solid. Earth's crust is broken into huge plates that move apart or push together at about the rate our fingernails grow. Convection of semi-molten rock in the upper mantle helps drive plate tectonics. When plates meet, one can slide beneath another. Plumes of magma rise from the edges of sinking plates. Thinned or fractured crust allows magma to rise to the surface as lava. Most magma doesn't reach the surface but heats large regions of underground rock.
- The deeper you go, the hotter it is !!! It’s simply the heat energy of the earth, generated by various natural processes, such as: 1. heat from when the planet formed and accreted, which has not yet been lost 2.decay of radioactive elements 3.friction etc……
- Rainwater can seep down faults and fractured rocks for miles. After being heated, it can return to the surface as steam or hot water. When hot water and steam reach the surface, they can form fumaroles, hot springs, mud pots and other interesting phenomena. When the rising hot water and steam is trapped in permeable and porous rocks under a layer of impermeable rock, it can form a geothermal reservoir.
- Many areas have accessible geothermal resources, especially countries along the circum-Pacific "Ring of Fire," spreading centers, continental rift zones and other hot spots. Volcanoes are obvious indications of underground heat. Geologists explore volcanic regions to find the most likely areas. Geologists and drillers study the data to decide whether to recommend drilling. Geothermal reservoirs suitable for commercial use can only be discovered by drilling. First, a small- diameter "temperature gradient hole" is drilled (some only 200' deep, some over 4000 feet deep) with a truck-mounted rig to determine the temperatures and underground rock types
- Direct Sources function by sending water down a well to be heated by the Earth’s warmth. Then a heat pump is used to take the heat from the underground water to the substance that heats the house. Then after the water it is cooled is injected back into the Earth.
- To harness energy, large holes have to be dug into the earth until a geothermal hotspot is found. Pipes are inserted inside these holes through which water is sent and steam output is obtained. The production involves two process: 1) Converting Geothermal energy into Mechanical energy 2) Converting Mechanical Energy into Electrical Energy The water is sent through the injection well and reaches the rocks and then hot water comes from the production well. The steam that comes out of the mixture might have dissolved brine and some dust particles. Due to the high pressure when it reaches the topmost of the earth surface it is converted into steam. The high pressure and low pressure steam runs the turbine. The generator is coupled with turbine to produce electricity. The condensor is a phase changer where the steam output of the turbine is given to the condensor and gets converted to hot water. This hot water is then sent to the cooling tower where it loses it heat and then sent to the geothermal reservoir for further production of steam.
- Like all steam turbine generators, the force of steam is used to spin the turbine blades which spin the generator, producing electricity. But with geothermal energy, no fuels are burned.
- Dry steam plants are the simplest and oldest design. They directly use geothermal steam of 150°C or greater to turn turbines. The Dry Steam technology allows for the steam from a geothermal production well to be fed directly to a steam turbine without a secondary heat exchanger. The turbine then coverts the change in steam pressure to mechanical rotational energy, which is converted to electrical energy by a generator.
- The boiling point of a fluid increases as its pressure is increased. When the pressure is reduced the water flashes to steam. Superheated water pumped from the ground at temperatures of 175 °C or more. It can be flashed to steam in a separator or flash tank to drive a turbine directly. Surplus water from the flash plant is reinjected into the ground. This is the most common type of plant in operation today.
- Binary cycle power plants are the most recent development, and can accept fluid temperatures as low as 57°C. The moderately hot geothermal water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to flash vaporize, which then drives the turbines. This is the most common type of geothermal electricity plant being constructed today. The thermal efficiency of this type plant is typically about 10–13%.
- In ground that is hot but dry, or where water pressure is inadequate, injected fluid can stimulate production. Developers bore two holes into a candidate site, and fracture the rock between them with explosives or high pressure water. Water travels through fractures in the rock, capturing the rock's heat until forced out of a second borehole as very hot water. The water's heat is converted into electricity using either a steam turbine or a binary power plant system. All of the water, now cooled, is injected back into the ground to heat up again in a closed loop. This approach is called hot dry rock geothermal energy in Europe. EGS systems are currently being developed and tested in France, Australia, Japan, Germany, the U.S. and Switzerland.
- The main disadvantage is that few locations on the planet are suitable for a good geothermal power plant. The reason is that the location must be close enough to the earth’s crust that a hole can be dug to access the heat. Most regions are not this close, making the most suitable locations those near fault lines or volcanoes. Another disadvantage is that nothing lasts forever. Some plants will generate a lot of electricity for 10 years then one day stop producing. As the earth’s crust shifts with small earthquakes, the heat source can disappear, making that geothermal plant useless.