Geothermal Energy: A Clean and Renewable Energy

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What is Geothermal Energy?

The term geothermal comes from the Greek geo meaning earth and therine meaning heat thus geothermal energy is energy derived from the natural heat of the earth. The heat that flows from the Earth's hot interior due to crustal plate movements, zones of high heat flow, may be located close to the surface where convective circulation plays a signifcant role in bringing the heat close to the surface (World Bank Group, 2012).

The Earth's crust, on which we live and depend, is in large part the product of millions of once-active volcanoes and tremendous volumes of magma that did not erupt but instead cooled below the surface. Such persistent and widespread volcanism has resulted in many valuable natural resources throughout the world. ... Groundwater heated by large, still-hot magma bodies can be tapped for geothermal energy. -- Excerpt from: Brantley, 2014, Volcanoes of the United States, USGS General Interest Publication

Deep circulation of groundwater along fracture zones will bring heat to shallower levels, collecting the heat flow from a broad area and concentrating it into shallow reservoirs or discharging as hot springs. These reservoirs may contain hot water and/or stream. By drilling into these reservoirs, the hot water and/or steam is piped to the surface where it is used for direct use applications, or the high pressure steam is separated to drive turbines for power generation. The low energy waste water form such power generaiton is then usually re-injected back into the reservoir, or further utilised for direct heat applications. This technology enables it to be utilised to generate electricity and provide domestic and industrial heat. Geothermal energy has proven to be reliable, economic, environmentally friendly and renewable (World Bank Group, 2012).

In general there are two main categories, (1) the high temperature resources and (2) the moderate/low temperature resources. The high temperature geothermal resources - 220 degrees Celsius and up - are predominantly found in volcanic regions and island chains. The moderate to low temperature resources are found on all continents. The high temperature are almost always used for power production while most of the low temperature resources are used for direct heating purposes or agriculture and aquaculture.

How does Harnessing Geothermal Energy Work?

Deep wells, a mile or more deep, can tap reservoirs of steam or very hot water that can be used to drive turbines which power electricity generators. There are 3 types of geothermal power plants in use today, and they are:
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