1.1 INTRODUCTION AND DEFINITION
Geothermal energy is the utilization of heat present in the deep earth for the purpose of power generation or other direct use application. In general terms, geothermal energy consists of the thermal energy present in the Earth’s crust. Thermal energy in the earth is distributed between the constituent host rock and the natural fluid that is contained in its fractures and pores at temperatures above ambient levels. Globally, the most commonly used geothermal resources for power generation are convective hydrothermal systems that are found in high heat flow and volcanic regions associated with tectonic plate boundaries such as west coast of the USA, New Zealand, and Indonesia. These resources …show more content…
For the case of hydrothermal systems, one normally needs to have large amounts of hot, natural fluids contained in an aquifer with high natural rock permeability and porosity to ensure long-term production at economically acceptable levels.
Geothermal energy is considered a renewable resource because the heat emanating from the interior of the Earth is unlimited. Mainly this heat is extracted by circulating a fluid through the reservoir to bring the heat to the surface where it can be used mainly in three ways:
I. Electricity Production
II. Direct use applications
III. Geothermal heat pumps
I. Electricity Production – The process of electricity production from geothermal energy is same as that of conventional coal fired power plant except the generation of steam in the former is from natural geothermal resource. Generated steam powers the turbine/generator to produce electricity. Geothermal energy is tapped by drilling wells into the reservoirs and piping the hot water or steam into a power plant for electricity production. The temperature, pressure, and fluid content of reservoir determine the type of power plant. There are three types of geothermal power plants:
Dry …show more content…
Economics can be improved with this approach, since the capital cost plays an important role for setting up the cost of electricity of geothermal systems.
1.3 TYPES OF GEOTHERMAL RESOURCES
Geothermal energy comes from the natural generation of heat mainly due to the decay of the naturally occurring radioactive isotopes of potassium, thorium and uranium in the earth. The estimated total thermal energy above mean surface temperature to a depth of 10 km is 1.3 x J, equivalent to burning 3.0 x barrels of oil. Since the global energy consumptions for all types of energy, is equivalent to use of about 100 million barrels of oil per day, the Earth’s energy to a depth of 10 kilometers could theoretically supply all of mankind’s energy needs for millions of years.
On average, the temperature of the Earth increases about 30˚C/km above the mean surface ambient temperature. Thus, assuming a conductive gradient, the temperature of the earth at 10 km would be over 300˚C. However, most geothermal exploration and use occurs where the gradient is higher, and thus where drilling is shallower and less costly. These shallow depth geothermal resources occur due