ABSTRACT
The geothermal resources of the earth are huge. The part of geothermal energy stored at a depth of 3 km is estimated to be 43,000,000 EJ corresponding to 1,194,444,444 TWh (Bijörnsson et al. 1998). Even this small part (<1%) that corresponds to the currently available share, and can be extracted economically using existing technology, is vast compared to the total world net electricity generation, which is expected to grow from 16,424 TWh in 2004 by 85% to reach 30,364 TWh in the year 2030 (EIA 2007). Geothermal resources are also much larger compared to all fossil fuel resources put together, whose energy and electricity equivalents are 36,373 EJ and 1,000,400 TWh, respectively corresponding to (1) oil: 1317.4 billion barrels (corresponding to 8062 EJ or 223,900 TWh), (2) natural gas 6183 trillion cubic feet (corresponding to 6678 EJ or 185,500 TWh), and (3) coal: 998 billion short tons (corresponding to 21,634 EJ or 600,900 TWh) (EIA 2007). If we consider that only a small part of the geothermal energy resources can be tapped for example, from either low-enthalpywet geothermal systems (WGS), or enhanced geothermal systems (EGS) applying artificial fracturing of the geothermal reservoir in both cases using advanced heat exchanger technologies which reduce the minimum fluid temperature required for power generation, the world geothermal resource will remain available for future generations long after the last drop of oil is exploited. Continuous development of innovative drilling and power generation technologiesmakes this source the best future option available to meet the required future electricity demand of the world, drastically reducing greenhouse gas emissions and mitigating global climate change.
