GEOTHERMAL

Geothermal Energy: **  Heat from deep within the earth is called "geothermal energy." In some locations, geothermal energy is close enough to the surface that, by drilling a well to reach the heat source, the energy can be extracted and used for heating buildings and other purposes. The centre of the Earth is around 6000 degrees Celsius - easily hot enough to melt rock. Even a few kilometres down, the temperature can be over 250 degrees Celsius. In general, the temperature rises one degree Celsius for every 36 metres you go down. In volcanic areas, molten rock can be very close to the surface, sometimes we can use that heat. Geothermal energy has been used for thousands of years in some countries for cooking and heating. Geothermal energy is literally heat from the Earth. Resources of this energy range from the shallow ground, to hot water and hot rock a few miles beneath the Earth's surface, and even deeper to the extremely high temperatures of molten rock. 'Hot rock' energy is a vast, environmentally friendly, economically attractive energy source which is clean and sustainable. ** Hot rocks underground heat water to produce steam. We drill holes down to the hot region steam comes up, is purified and used to drive turbines, which drive electric generators. **Where its being used:** The first geothermal power station was built at Landrello, in Italy, and the second was at Wairekei in New Zealand. Others are in Iceland, Japan, the Philippines and the United States.
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 * How it Works:


 * Geothermal technologies include:**
 * 1) [|Conventional geothermal]
 * [|Binary cycle power plants], which pass moderately hot geothermal water by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to flash to vapor, which then drives the turbines. This is the most common type of geothermal[|[][|5][|]], both [|ORC] and [|Kalina] cycles are used.
 * [|Hot dry rock geothermal energy]: Using deep wells into hot rock, a fluid is heated and used to generate power. Also known as EGS or [|Enhanced Geothermal Systems]
 * Dry steam plants, which directly use geothermal steam to turn turbines;
 * Flash steam plants, which pull deep, high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines; and
 * 1) [|Direct heat]: Hot water near Earth's surface can be piped directly into facilities and used to heat buildings, grow plants in greenhouses, dehydrate onions and garlic, heat water for [|fish farming], and pasteurize milk. Some cities pipe the hot water under roads and pavements to melt snow. [|District heating] applications use networks of piped hot water to heat buildings in whole communities.[|[][|5][|]]
 * 2) [|Geothermal heat pump]: Almost everywhere, the upper 10 feet (3.0 m) of Earth's surface maintains a nearly constant temperature between 10 and 16° celsius (50 and 60° F). A geothermal heat pump system consists of pipes buried in the shallow ground near a building, a heat exchanger, and ductwork into the building. In winter, heat from the relatively warmer ground goes through the heat exchanger into the house. In summer, hot air from the house is pulled through the heat exchanger into the relatively cooler ground. Heat removed during the summer can be used as no-cost energy to heat water.[|[][|5][|]]
 * [|Direct exchange geothermal heat pump]: A heat pump without a heat exchanger, which circulates the working fluid through pipes in the ground.


 * **ADVANTAGES** || **DISADVANTAGES** ||
 * Requires no fuel, isn't affected by fluctuating fuel prices || Geothermal fluid is corrosive ||
 * Emission free || Lots of heat energy lost ||
 * Unlike solar and wind energy, doesn't rely on a transient source of energy || Can negatively affect land stability in surrounding region ||
 * Inexhaustable, replenished from deep in the earth || Water from geothermal sources may contain dangerous chemicals, unsafe to drink ||
 * Minimal land use requirements || Geothermal sites may cool down, take a long time to replenish; have to be left alone for a hwile to recover lost heat ||
 * Scaleable; large plant to power big city, small plant to power more remote areas ||  ||