Av Henrik Holmberg, stipendiat ved Fakultet for ingeniørvitenskap og teknologi, Institutt for energi- og prosessteknikk, NTNU
Geothermal energy has received increasingly international interest
during the recent years. One example of this is the yearly geothermal conference
at Stanford University in USA where both the number of publications and participating
countries has increased rapidly during the last 5 years. Geothermal energy is
commonly used both for heating demands and for electricity production and the
theoretical potential is enormous. In a MIT-rapport from 2006 it is estimated
that the resource can contribute with up to 100.000 MW electricity
in USA within the next 50 years [1].
Geothermal energy referrer to the thermal energy that is produces in
earth’s crust through breakdown of radioactive isotopes and the heat that is
transported outwards from earth’s interior.
The concept geothermal energy includes both deep geothermal energy systems
where heat is mined from depths of several kilometers and shallow geothermal
systems where wells with depths of a few hundred meters are used in ground
source heat pump (GSHP) systems. While shallow geothermal energy is indeed an
important part of the geothermal sector, deep geothermal energy is the focus
for this text.
Deep geothermal energy has long been tightly associated with the
geographically constricted and naturally occurring hydrothermal systems in
volcanic active regions, see figure 1. In recent years it has been pointed out
that engineered geothermal systems (EGS) can provide a way for geothermal
energy to grow outside its geographical constraints and thereby to reach a
significant share of its huge global potential.
Figure 1. Manifestation of hydrothermal system in
Iceland.
