1. How does the geothermal energy work ?
Maximilien CARRE
Angele VANBECELAERE

2. Content Introduction Geothermal reservoirs
Extraction and uses of Geothermal energy
Electricity generation
Geothermal energy in Roumania
Conclusion

3. Introduction
Geothermal Energy has been around for as long as the Earth has existed. "Geo" means earth, and "thermal" means heat.
Below the crust of the earth, the top layer of the mantle is a hot liquid rock called magma.
For every 100 meters you go below ground, the temperature of the rock increases about 3 C. So, if you went about 10,000 feet below ground, the temperature of the rock would be hot enough to boil water.
Deep under the surface, water makes its way to the hot rock and turns into boiling hot water or steam. The hot water can reach temperatures of more than 300 F (148 C). It doesn't turn into steam because it is not in contact with the air.
When this hot water comes up through a crack in the earth, we call it a hot spring. Or, it sometimes explodes into the air as a geyser.
In other places around the world, people used hot springs for rest and relaxation. The ancient Romans built elaborate buildings to enjoy hot baths, and the Japanese have enjoyed natural hot springs for centuries.

4. Geothermal reservoirs
A subsurface region where the rocks contain hot water and/or steam that can be withdrawn using wells and put to practical use for direct heating or for generating electricity
Essential Elements of a Geothermal Reservoir
High temperature
Working fluid (water and/or steam)
Permeable flow channels
Geothermal reservoirs are usually found in fractured volcanic rocks.
Permeability of a geothermal reservoir is usually found in discrete fractures, not intergranular pores.
Vertical dimensions of permeable reservoir zone can be large (comparable to horizontal dimensions).
Natural condition is dynamic, not static.
Geothermal reservoir is in a continuous state of convective flow, which carries heat from deep underground to exploitable depths.
Resource is heat, not mass. Brine acts as a working fluid which can carry energy stored in hot rock to the surface through wells.
In most liquid-dominated reservoirs, over 80 percent of the total heat is stored in rock— vapor-dominated, over 95 percent.
Production/injection wells create artificial circulation system to mine energy from the rock.
Geothermal reservoirs
A subsurface region where the rocks contain hot water and/or steam that can be using and put to practical use for direct heating or for generating electricity
Essential Elements of a Geothermal Reservoir :
- High temperature
- Working fluid (water and/or steam)
- Usually found in fractured volcanic rocks.
- Resource is heat. Brine acts as a working fluid which can carry energy stored in hot rock to the surface through wells.
- In most liquid-dominated reservoirs, over 80 percent of the total heat is stored in rock— vapor- dominated, over 95 percent.

5. Extraction and uses of geothermal energy
The heat energy can be brought to earth surface by following ways :
Directly from hot springs/geysers
Geothermal heat pump
Uses are bodly classfied as :
Direct use (use hot springs to heat the greenhouse)
Indirect use (electricity production)

6. Electricity generation
There are 3 types of power plants:
Dry steam power plant
This plant use the steam to make turbines tourned and the steam return in the earth.
Flash steam power plant
This plant use steam and water to make turbine rotating and the steam and the water return in the earth.
Binary cycle power pant
This plant use two cycle. One with hot water which heat the other one. And this other one make turbine rotating. The hot water of the primary cycle return into the earth.

7. Geothermal energy in Roumania

8. Conclusion
Using geothermal energy reduce annual cost of heating house by more than 60 %
Most of geothermal plants are situated in the US
Geothermal energy have a good efficiency