How does a geothermal plant work?
In a geothermal power plant thermal energy coming from hot rocks which are located inside the earth, transmitted to water which has been absorbed by the ground. The thermal energy of the rock comes either directly or indirectly from nuclear radiation.
The water emerges at the surface in the form of steam. This hot water is used to heat water in the secondary circuit which is converted to water under pressure that means it obtains kinetic energy. The steam is used to turn the turbine. Only  part of the kinetic energy of the steam is converted into kinetic energy in the turbine.
A part of the kinetic energy of the turbine is converted into kinetic energy to the generator and finally to electrical energy.
After rotating the turbine the temperature of the steam falls and can not be used to rotate a second turbine. Though the water is still hot enough and it is used for heating homes in the nearby area, as hot water in houses, for hot water in swimming pools, for heating greenhouses, etc.

Do geothermal factories
affect the environment?  more info 

Geothermal factory in detail.

How the water is heated? 

Low temperature geothermal areas.

Is geothermal energy renewable? 

more info
more info
© 2003, Despina M. Garyfallidou Athens-Greece