Environmental Engineering Reference
In-Depth Information
Figure 7.3
The Geothermal Power Plant Fuel Cycle
Power plant
development
Exploration
Field development
Reclamation and
waste disposal
Electricity production
and transmission
Utilization
2007, 12). The environmental costs of utility-scale geothermal power plants include significant
land disturbance and land use impacts, air emissions, hazardous materials disposal, noise pollu-
tion, and potential impacts on water and other resources, depending on the location of the resource
and the geothermal technology design employed. The environmental costs of geothermal electric
power production are on a par with more conventional technologies for bulk electric power pro-
duction in use today. Electricity generation using geothermal power plants entails much greater
and more concentrated environmental costs than those from geothermal heat pump use, which
are less severe and more dispersed.
Exploration
Exploration and reservoir evaluation activities include geological, geophysical, and drilling sur-
veys for exploratory drilling and reservoir testing (IFC 2007, 12). The objective is to locate areas
underlain by hot rock; estimate the volume of the reservoir, the temperature of the fluid in it, and
the permeability of the formation; predict whether the produce fluid will be dry steam, liquid, or
a mixture; define the chemical nature of the fluid; and forecast the electric power potential for a
minimum of twenty years. To accomplish this, a survey of published literature, an airborne survey,
and surveys of geology, hydrology, geochemistry, and geophysics must be undertaken in a target
area (DiPippo 2008, 20-21). Drilling of test wells must be undertaken, with construction of roads,
well pads, and pipelines having impacts similar to those described for oil and gas in
Chapter 4.
Power plant buildings and a substation must be constructed.
Production field development after a geothermal resource has been located and characterized
involves drilling steam or hot water production wells and reinjection wells and processing reservoir
output for use in a power plant. Drilling continues throughout the life of a project, as production
and injection wells need to be periodically renewed to support power generation requirements
(IFC 2007, 12).
Air Pollution and Hazardous Waste
Operational activities include operation and maintenance of the geothermal power generating
plant, well field monitoring and maintenance, periodic drilling of production and injection
wells, geothermal fluid processing, and pipeline maintenance. Superheated geothermal fluids
typically contain a number of dissolved metals and gases, including methane, ammonia, hy-
drogen, and nitrogen (Armaroli and Balzani 2011, 249; Barbier 2002). The main toxic gases
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