Geothermal energy and strategies to
reduce greenhouse gas emissions
C. Fouillac
Research Direction
ENGINE LAUCHING CONFERENCE ORLEANS 13-02-2006
The climate challenge for the 21st century
« Business as usual »  ΔT > 6°C
 ΔT < 2°C
Special report «Carbon Dioxide Capture and Storage »
IPCC, September 2005
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For the next 50 years: the stabilization triangle
Pr Robert H. Socolow (Princeton University)
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What is a Wedge?
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It is a strategy which allows the reduction of carbon
emissions; its effects grow in 50 years from 0 GtC
avoided/year to 1 GtC avoided/year. To count in the next fifty
years, this strategy must have been demonstrated somewhere
today ,even at a small scale
Total = 25 Gt of Carbon
1 GtC av.
/yr.
50 years
In a cumulative way, a wedge, during its first 50 years
of functioning, divert from the atmosphere ,
a carbon flux of 25 Gt
A « solution » to the CO2 problem should provide a Wedge
or a noticeable fraction of a wedge
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Geothermal energy contribution to CO2 emission
stabilisation
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In 2003,the World running capacity of Geothermal power
plants accounted to 8 GWe and produced 57 000 GWh
(Bertani WGC 2005)
Substituting a similar production to coal fired power
plants during 50 years would account for 1/25 of a wedge
According to Stefanson (WGC 2005), the to day installed
capacity is probably not much than 5% of the actual
resource.
Direct uses are difficult to estimate but are very important
and rapidly growing.
This preliminary figures do not take the potential impact of
EGS into account.
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Geothermal energy: Heat and power generation
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Extrapolated temperatures at 5km depth in Europe
< 60° C
60°- 80°C
80°- 120°C
120°- 140°C
140°- 160°C
160° - 180°C
180°- 200°C
200°- 220°C
220°- 240°C
> à 240°C
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Pannonian Bassin : T°C at 5000m depth
(Genter et al 2004)
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Locating the EGS resource :
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3D predictive modelling of lithology, temperature,
permeability and stress distribution
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Resource assessment: “Changing the Scale”
•
•
•
Europe has produced in the nineties a” European Atlas of geothermal
resources”
Though very useful, this document has not the appropriate scale to reduce
the geological risk to an acceptable level for the promotion of EGS
projects
European Commission must encourage the member states to refine their
geothermal potential assessments. This can produce a digital map (GIS)
,compatible with other information levels,easy to modify and improve,
where detailed knowledge can be added as soon as it will be available.
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Drilling to the HDR / EGS reservoir : costs repartition
100%
90%
80%
Opération
Operation et
and
maintenance %
%
Unité
de productions
Power
plant %
%
70%
60%
50%
Reservoirdu
Stimulation
stimulation
réservoir
%%
Forage
%%
Drilling
40%
30%
20%
10%
0%
1
2
1 : gradient 20°C/km
3 : gradient 60°C/km
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2 : gradient 40° C/km
4 : gradient 80°C/km
Modified after A. J. Tester (1994)
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Drilling geothermal wells
> Difficult and challenging: hot, hard, fractured
rocks, corrosive fluids
> Compared to oil and gas well drilling, it’s a
very small market (~3 Geothermal wells for
1000 Oil and Gas wells)
> Foreseen improvement
•
•
•
M.W.D. for inclined wells
Cutting tools
Particle impact drilling
•
•
Thermal spallation drilling?
Laser drilling ?
> Technological breakthrough
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Nikola Tesla ’s patent: an ancestor for Hot Dry Rock
geothermal exploitation
« All that is necessary to open up
unlimited resources of power
throughout the world is to find
some economic and speady way
of sinking deep shafts »
Nikola Tesla 1931
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Stimulating the reservoir
> Develop a heat exchanger large enough to
sustain the production during say, 25 years
without thermal decline
> Keep water losses below acceptable levels
1% ,5% ? (depends on water availability and
supply cost)
> Keep hydraulic impedance below 1l/s/bar
•
this threshold is a site specific function of the energy output
and of the pumping energy penalty; it is more or less
directly related to the temperature of the reservoir
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Efficient and Optimal use of E.G.S.
> Thermal energy extraction from the reservoir
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•
•
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Develop new concepts for injection/ production well position
and completion
Develop innovative approaches of chemical stimulation
Develop new concepts of heat extraction “Supercritical CO2
for down hole circulation fluid and working fluid”
Heat and power production schemes
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•
•
From site to site, it could be more appropriate to deliver
power or heat , or both
Improve the cost and efficiency of heat- power conversion
schemes( heat exchangers, binary cycles, low cost turbines)
Develop hybrid schemes (ex: Hybrid EGS- fossil fired power
plant, with high energy efficiency and reduced CO2
emissions)
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Conclusions
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Geothermal energy can play a very significant role among the
CO2 reduction strategies.
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Today, many geothermal direct uses provide very efficient
ways for CO2 reduction but, only hydrothermal reservoirs of
high grade resources are used for power production
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On the long term (50 years, 100 years) EGS technology has a
high potential in continental Europe to increase the
contribution of geothermal energy to the reduction of CO2
emissions
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Engine Coordination Action will allow to develop a
development of European research efforts and support
international cooperation
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