Geothermal energy?? Center of the earth heat utilization
Geothermal energy?? Center of the earth heat utilization
What is geothermal
Earth's interior is very hot, the earth's core temperature is about 4000 , heat flows continuously in the ground, out and away from the surface radiation in space. The average surface heat energy value of 82 mW / m 2, if the Earth's surface area is 5.1 1014 m 2, then this continuous heat loss rate of about 42 trillion MW (thermal).
To the surface energy of the majority is very poor heat, rarely collected and used directly. However, nearly a hundred million years of volcanic activity occurred between the areas, a large number of high-quality heat retention in the crystallization of lava or 2 to 10 km deep rock, with modern technology (such as the rock drilling) can be collected effectively.
Extract heat from the crustal rocks and transported to the surface, heat transfer media needs. Nature through the groundwater to achieve this. Geothermal heat beneath the lava library groundwater heating, hot water through the rocks of interconnected faults, cracks and holes in the surface. Faults, cracks and holes in the rock volume of open space accounts for only 2% to 5%, but when they are filled with water and connected, will form a porous permeability geothermal library.
Geothermal water at a temperature can vary greatly with another. Some places can produce heat above 300 hot water, some are produced below boiling point, (boiling point of water at sea level 100 ) water. Higher than 150 high temperature heat source generally used to generate electricity for direct heating using low temperature heat source, such as industrial processes, district heating, greenhouse heating, food drying, and aquaculture.
Geothermal power
Geothermal power, steam power generation in fact. Wells are found on the jet by the natural heat flow. As the water is from 1 to 4 km deep underground up, so water is at high pressure. A bottom diameter of 25 cm per hour, the wells can produce 20 to 80 million kg of geothermal water and steam. As the temperature difference, 5 to 10 wells and a power output of the steam plant can produce 55 megawatts of electricity.
This power plant has two kinds: steam turbine power generation and binary plant. In order to supply a steam turbine generator, out of the ground water (with pressure) in the flash tank known as the release surface of the container, some water (about 35%, depending on its temperature) flash (boiling) steam into the turbine engine and then drive a generator. Turbine exhaust the traditional cooling tower cooling. Flash tank of water remaining in the boiling hot into the library followed by the edge of the ground, it helps to maintain the pressure and added heat Library hydrothermal convection system.
In the binary power generation device, not the hot flash to steam, but sent to a heat exchanger for heating the working medium, which are usually organic compounds, such as isobutane or isopentane. Working medium is gasification, gasification with steam-driven turbine engine after, and then drive generators. Work after leaving the turbine medium condensate liquid, flow back into the heat exchanger again gasification. Geothermal fluid back underground through injection wells, and the generator in this case are similar. As in the binary geothermal power plant used in the work of the medium is lower than the temperature of water evaporation, so its power generation efficiency higher than the turbine.
These two types of power generation devices have their advantages. Turbine manufacture and operation are not too expensive, but in order to operate in high efficiency, it requires water temperature above 180 ~ 200 . Binary power plant manufacturing and operating costs high, but it can be 100 or more low temperature water power. Most of the world is running geothermal power plant is steam turbine type, but more and more popular binary power plant.
The sustainability of geothermal
Magmatic / volcanic and geothermal activity in the typical life of a minimum of 5,000 years from more than 100 years. Such a long life so that to become a renewable energy heat source. In addition, geothermal natural rate of replenishment of the library from a few megawatts to 1,000 megawatts (thermal) or more.
The first generation of human land use hot water in drag Tuscany, Italy 1904. New Zealand's North Island began in 1958, land heat generation (currently 212 MW); fountain California geothermal field, started power generation in 1960, the current output of 1,300 megawatts. Clearly, geothermal resources are reliable, safe and sustainable way to run.
The sustainability of geothermal production can also be present in the thermal reservoir rocks from (including heat 85% to 95%) in the heat source to judge. The fountain in the geothermal field in California, a conservative estimate the heat content equivalent to burning at least 280 million barrels of oil or 6.2 billion short ton (1 short ton = 907 kg) of coal derived energy.
The prospects for geothermal energy
As the world demand for clean energy will be greater use of geothermal energy. Geothermal resources around the world everywhere, especially in many developing countries, especially rich, they can replace the use of fossil fuel power plant pollution caused. This is very important, because once on the fossil fuel power plants to make investments in the life of the plant during the flow of air pollution will be issued, its period is several decades.
Present in 25 countries around 8000 megawatts of geothermal power will soon put into use. In addition, the Philippines, Indonesia and New Zealand will add 700 megawatts of geothermal power. To the end of 1997, the world's installed capacity of geothermal power 7950 MW.
Last put into use in the geothermal field is the Geysers in the United States, will produce 1,300 megawatts of electricity, enough to meet the 1.3 million households in California's electricity. It is estimated that the volcanic system of the developing world can be made from 80,000 MW geothermal power. Indonesia's geothermal potential of 19,000 megawatts reached. Geothermal power plant the size of about 300 kW to 55 MW (net electric power).
Direct application of geothermal worldwide use in 9000 megawatts (thermal power) above. Ireland almost all of the family land and buildings are hot. Several cities in the United States and New Zealand also use geothermal energy for heating. Many countries have geothermal heating the greenhouse. Food processing is another mature application. Direct application of geothermal resources around the world the great potential of virtually untapped.
On geothermal research and development will eventually make human can use with the rock at different depths and not just the huge volcanic geothermal areas. Once this stage, geothermal energy to supply electricity and heat required for the world of 25% to 50%.
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