Geothermal Energy Sources

Hot Spring

Geothermal energy is clean and sustainable source of energy. Heat obtained from the earths crust can be used in many ways, from large power station to relatively small pumping system.Resources of geothermal energy is found in shallow ground to hot water and hot rock found few miles beneath the earth.
The energy present in the earth's crust which is in the form of heat such energy is called geothermal energy.
The uppermost crust up to 10 km or so of the earth's crust constitutes a potentially useful and almost inexhaustible source of energy.

Heat Extraction

In the above  representation of geothermal energy, at depth of 5-10 km or so lies impermeable magma and the magma are impermeable crystalline rocks which are overloaded by pockets of permeable rock . This localized pockets are founded by the fracture zone or faults around which some relative motion of rock has occurred.
Water is circulated along with the fault lines and moves in the earth's interior path. It is heated by permeable rock or layer which is in term heated by conduction of heat from the magma. The hot water comes out through another fault and forms a hot spring.
Availability of Geothermal Energy:-

Depending on the temperature and depth of the the permeable rock the natural hydro thermal systems can be divided into three categories:

1. Dry Steam System:- The temperature of permeable rock is very high. The whole of the water is converted into steam which is converted into steam which gets superheated by the time comes out on surface.
2. Wet Steam System:- The temperature of permeable rock is not very high.By the time water comes out on the surface only a part of it is get converted into steam therefore the eruption gives a water-steam mixture. 
3. Hot water System:- The temperature of permeable rock is rather low, therefore the surface eruption provides hot water. 

Vapour Turbine Cycle

Vapour Turbine Cycle

Recently in Geothermal plants heat exchanger and vapour turbine cycle have been proposed for generation. The geothermal hot water is used to heat for low boiling point fluids (Propane/Freon). This fluid expands in turbine which drives the generator. The fluid is condensed and reused to form a closed circuit system in vapour turbine cycle system. The low enthalpy geothermal water can also be profitably used.
It should be noted that electricity generated by California based Geothermal Power Plants(USA) is almost half of electricity generated by Geothermal Power Plants.

Geothermal Electricity Plant - California (USA)

Geothermal energy is also used for heating purposes.There are many examples of direct using of geothermal energy for heating purposes as for drying out fish, to heat greenhouses, for improving oil recovery, fish farms, etc. Around the world, people also used hot spring for relaxation and rest.

Advantages:

Geothermal energy has many advantages as follow:

1. Reliability:- Unlike other Non Conventional energy sources such as Wind, Tidal and Solar, Geothermal energy is reliable as it provides constant power.
2. Geothermal energy is environment-friendly. There is a very less or we can say no pollution is produced by Geothermal Plant. Although fumes are not produced while drilling the earth. Therefore there is no adverse effect on environment.
3. The pollution can be reduced somewhat by increasing use of Geothermal as well as other non conventional energy sources which is caused by use of many conventional fuels like oil, coal, etc.
4. Geothermal energy has many application. For instance it can be used to generate electricity as well as for providing heat to home and businesses.