Summaries
Technical Summary
Electric or Thermal [EJ/yr]
Electricity
4.3
Thermal
Technology and applications
1200
Geothermal energy is currently extracted using wells and other means that produce hot fluids from: (a) hydrothermal reservoirs with naturally high permeability, or (b) Enhanced or engineered geothermal systems (EGS) with artificial fluid pathways (Figure TS.4.2). Technology for electricity generation from hydrothermal reservoirs is mature and reliable, and has been operating for about 100 years. Technologies for direct heating using geothermal heat pumps (GHPs) for district heating and for other applications are also mature. Technologies for EGS are in the demonstration stage. [4.3]
1000
800
600
400 Max
200
Electric power from geothermal energy is especially suitable for supplying base-load power, but also can be dispatched and used to meet peak demand. Hence, geothermal electric power can complement variable electricity generation. [4.3]
Min
0 10
5
3
Direct Uses
Depth [km] Figure TS.4.1 | Geothermal technical potentials for electricity and direct uses (heat). Direct uses usually do not require development to depths greater than about three km. [Figure 4.2]
potentials for each country, and then countries are grouped regionally. Thus, the present disaggregation of global technical potential is based on factors accounting for regional variations in the average geothermal gradient and the presence of either a diffuse geothermal anomaly or a high-temperature region associated with volcanism or plate boundaries. The separation into electric and thermal (direct uses) potentials is somewhat arbitrary in that most higher-temperature resources could be used for either, or both, in CHP applications depending on local market conditions. [4.2.2] The heat extracted to achieve the technical potentials can be fully or partially replenished over the long term by the continental terrestrial heat flow of 315 EJ/yr at an average flux of 65 mW/m2. [4.2.1]
Since geothermal resources are underground, exploration methods (including geological, geochemical and geophysical surveys) have been developed to locate and assess them. The objectives of geothermal exploration are to identify and rank prospective geothermal reservoirs prior to drilling. Today, geothermal wells are drilled over a range of depths up to 5 km using conventional rotary drilling methods similar to those for accessing oil and gas reservoirs. Advanced drilling technologies allow for high-temperature operation and provide directional capability. [4.3.1] The basic types of geothermal power plants in use today are steam condensing turbines and binary cycle units. Condensing plants can be of the flash or dry-steam type (the latter do not require brine separation, resulting in simpler and cheaper plants) and are more common than binary units. They are installed in intermediate- and high-temperature resources (≥150°C) with capacities often between 20 and 110 MWe.
Table TS.4.1 | Geothermal technical potentials on continents for the IEA regions. [Table 4.3] Electric technical potential (EJ/yr) at depths to: 1
3 km
REGION
5 km
Technical potentials (EJ/yr) for direct uses
10 km
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
OECD North America
25.6
31.8
38.0
91.9
69.3
241.9
2.1
68.1
Latin America
15.5
19.3
23.0
55.7
42.0
146.5
1.3
41.3
OECD Europe
6.0
7.5
8.9
21.6
16.3
56.8
0.5
16.0
Africa
16.8
20.8
24.8
60.0
45.3
158.0
1.4
44.5
Transition Economies
19.5
24.3
29.0
70.0
52.8
184.4
1.6
51.9
Middle East
3.7
4.6
5.5
13.4
10.1
35.2
0.3
9.9
Developing Asia
22.9
28.5
34.2
82.4
62.1
216.9
1.8
61.0
OECD Pacific
7.3
9.1
10.8
26.2
19.7
68.9
0.6
19.4
117.5
145.9
174.3
421.0
317.5
1,108.6
9.5
312.2
Total
Note: 1. For regional definitions and country groupings see Annex II.
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