Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments 3.0 Renewable Energy Technology Options
3.9 Geothermal
Geothermal resources can provide energy for power production or a wide variety
of direct use applications. Geothermal power plants use heat from the earth to generate
steam and drive turbine generators for the production of electricity. There are three basic
types of geothermal technology: dry steam, flash steam, and binary cycle steam. Dry
steam power plants are suitable where the geothermal steam is not mixed with water, and
operate at high temperatures of between 356º to 662ºF (180º to 350ºC). Flash steam
power plants tap into reservoirs of water with temperatures greater than 360ºF (182ºC).
Binary cycle power plants operate on water at lower temperatures of 225º to 360ºF (107º
to 182ºC).
Figure 3-20. Geothermal District Heating Equipment.
As of 2002 the global installed capacity for geothermal power plants was
8,227 MWe (megawatt electrical). An additional 15,580 MWth (megawatt thermal) was
used in direct heat applications. It is estimated that geothermal resources using today’s
technology could support between 35,500 and 72,000 MWe of electrical generating
capacity. Using enhanced technology that is currently under development (permeability
enhancement, drilling improvements) geothermal resources have the potential to support
between 65,500 and 138,000 MWe. 43
43 Renewable Energy World, 2002
21 March 2005 3-74 Black & Veatch