Geothermal handbook: PlanninG and Financing power Generation t e c h n I c a L r e p o r t 2 / 2

F I g u r E 1 . 3
Schematic View of an Ideal Geothermal System
Source | Dickson and Fanelli 2004.

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G e o t h e r m a l H a n d b o o k : P l a n n i n g a n d F i n a n c i n g P o w e r G e n e r a t i o n 
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Figure 1.3 shows the components of a typical hydrothermal (steam or water based) volcanic-related 
geothermal system, which are, from bottom to top: 
• 
The magmatic intrusion (also called hot body, where hot magma intrudes exceptionally far
into the Earth’s crust) is often caused by tectonics of the continental plates.
• 
The actual geothermal reservoir is where hot steam or water are trapped under high pressure
beneath a tight, non-permeable layer of rocks and is heated by the magmatic intrusion below.
• 
The geothermal wells tap into the geothermal reservoir and access the hot steam or fluid,
then transfer it through pipelines to the power plant, after which the fluids are usually returned
into the reservoir.
• 
Fresh water or precipitation comes from recharge areas like lakes, rivers or the seas and
provides cold meteoric waters, which slowly seep through the ground to lower layers through
cracks and faults in the rocks.