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4.4 Geothermal

Geothermal energy is thermal energy generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials. The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.
(Source : https://en.wikipedia.org/wiki/Geothermal_energy#Types Links to an external site.)

Geothermal energy comes in either vapor-dominated or liquid-dominated forms. Hot water from the earth may be extracted to heat homes and buildings by directly circulating the hot water through buildings or  through a heat exchanger that transfers the heat to the building. And to generate electricity there are 2 ways:

 

  • Direct steam systems/vapor-dominated resources
    When the geothermal resource produces a saturated or superheated vapor (from 240 to 300 °C), the steam is collected from the production wells and sent to a conventional steam turbine. Before the steam enters the turbine, appropriate measures are taken to remove any solid debris from the steam flow, as well as corrosive substances contained in the process stream.
  • Flash steam systems/liquid-dominated resources
    In a single-flash cycle, a separator is used to separate the fluid phases, with the steam phase being sent to a turbine. In this cycle, the fluid pressure is reduced, which results in additional flashing of the liquid phase and produces additional steam flow. Once the steam leaves the separator, the cycle is very similar to that for a vapor-dominated resource. The saturated liquid brine leaving the separator is reinjected along with cooling tower blowdown and excess condensate.
    (Sourse : http://petrowiki.org/Converting_geothermal_to_electric_power Links to an external site.)

 For more theories please check Chapter 3.1 Thermodynamics

 

(Source : https://www.studentenergy.org/topics/geothermal Links to an external site.)

For the basic theories of generators please check Chapter 3.3 Electromagnetic Theory

 

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