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222 J. L. Renner
researchers are investigating methods to improve the productivity of natural
geothermal systems. If they are successful, the number of geothermal systems
available for production will dramatically increase. Tester et al. [3] suggest that
in the USA alone a modest research program could lead to 100 000 MW e of geothermal
generation online by 2050.
Ongoing research projects in the USA, France and Germany have indicated
that technology is available to enhance systems with low or no natural productivity
so that artificial or ‘ enhanced geothermal systems ’ can be engineered.
The researchers, however, have not yet demonstrated that sufficiently productive
and large systems can be created to ensure economic development. In order
to make geothermal a universal energy source, drilling engineers will need to
develop low-cost drilling capable of reaching usable temperatures in areas of
near-normal geothermal gradient.
10 . Sources of Additional Information
Further general information concerning geothermal energy is available on
many worldwide web sites. Among the more informative are Refs [18–23] .
Technical literature from many geothermal conferences, including publications
of the Stanford geothermal program and their annual geothermal workshop, is
available from a Stanford web page [24] . Stanford also hosts the International
Geothermal Association (IGA) Geothermal Conference Papers Database [25] .
References
1. Birch , F. , R. F. Roy and E. R. Decker ( 1968 ). Heat Flow and Thermal History New
England and New York . In Studies of Appalachian Geology: Northern and Maritime
( E. Zen , W. S. White , J. B. Hadley and J. B. Thompson , eds) , pp. 437 – 451 . Interscience
(John Wiley) , New York .
2. Diment , W. H. , T. C. Urban , J. H. Sass , et al. ( 1975 ). Temperatures and Heat Contents
Based on Conductive Transport of Heat . In Assessment of Geothermal Resources of the
United States – 1975 ( D. E. White and D. L. Williams , eds) , US Geological Survey
Circular 726 , pp. 84 – 103 .
3. Tester, J. W., B. J. Anderson, A. S. Batchelor, et al. (2006). The Future of Geothermal
Energy . Idaho National Laboratory External Report INL/EXT-06-11746, Idaho Falls,
ID, 396 .
4. Wisian , K. W. , D. D. Blackwell and M. Richards ( 1999 ). Heat Flow in the Western
United States and Extensional Geothermal Systems . Proceedings: 24th Workshop on
Geothermal Reservoir Engineering , SGP-TR-162, p. 219 , Stanford University , Stanford,
CA .
5. Blackwell, D. D. and M. Richards (2004). Calibration of the AAPG Geothermal
Survey of North America BHT Data Base. AAPG Annual Meeting , Dallas, TX, Poster
session, paper 87616.
6. Kearey , P. and F. J. Vine ( 1996 ). Global Tectonics , 2nd edn , p. 333, Blackwell Science ,
London .
7. Griggs, J. (2004). A Re-evaluation of Geopressured-geothermal Aquifers as an Energy
Resource , p. 81. M.S. thesis, Louisiana State University, Baton Rouge, LA.