Geothermal Power Plants

The source of geothermal energy.

• The solid crust of the earth is an average of 32 km deep. Under the solid crust is the molten mass, the magma.

• The heat stored in the magma is the source of geothermal energy.

• The hot molten magma comes close to the surface at certain points in the earth and produces volcanoes, hot springs, and geysers.

Hydrothermal Source

• This is the most developed source. Power plants, up to a capacity of 2000 MW, are in operation worldwide.

• Heat from the magma is conducted upward by the rocks. The groundwater drifts down through the cracks and fissures to form reservoirs when water-impermeable solid rock bed is present. The water in this reservoir is heated by the heat from the magma.

• Depending on the distance from the magma and rock configuration, steam, hot pressurized water, or the mixture of the two are generated.

• The reservoir is tapped by a well, which brings the steam-water mixture to the surface to produce energy.

The geothermal power plant concept

• The hot water and steam mixture is fed into a separator. If the steam content is high, a centrifugal separator is used to remove the water and other particles. The obtained steam drives a turbine. The typical pressure is around 100* psi and the temperature is around 200 ° C .

• The water is returned to the ground, the steam drives the turbine. Typically the steam entering the turbine has a temperature of 120 to 150 °C and a pressure of 30 to 40 psi.

• The turbine drives a conventional generator. The typical rating is in the 20- to 100-MW range.

Concept of a geothermal power plant

problems with geothermal power

• Major problems with geothermal power plants are the minerals and noncondensable gases in the water. The minerals make the water highly corrosive, and the separated gases cause air pollution.

• An additional problem is noise pollution. The centrifugal separator and blowdowns require noise dampers and silencers.

Measuring units conversion• Pounds per square inch (psi, PSI, lb/in2, lb/sq in)

Commonly used in the U.S., but not elsewhere. Normal atmospheric pressure is 14.7 psi, which means that a column of air one square inch in area rising from the Earth's atmosphere to space weighs 14.7 pounds

• Atmosphere (atm) Normal atmospheric pressure is defined as 1 atmosphere. 1 atm = 14.6956 psi = 760 torr

• Pascal (Pa) 1 pascal = a force of 1 Newton per square meter (1 Newton = the force required to accelerate 1 kilogram one meter per second per second = 1 kg.m/s2; this is actually quite logical for physicists and engineers, honest). 1 pascal = 10 dyne/cm2 = 0.01 mbar.

• 1 atm = 101,325 Pascals = 760 mm Hg = 760 torr = 14.7 psi.