Page 921 - Basic Electrical Engineering

hence the water surface of the ocean works as a solar collector. The warm
surface water of the ocean can be used to generate electricity. The warm
water of the ocean can be used to vaporize a working liquid of low boiling

point such as amonia. The vapour will expand and can run a gas turbine
which will drive a generator.

13.7.7 Electricity from Geothermal Energy

Heat energy is trapped in rocks inside the core of the earth. Water absorbs the
heat from these rocks and gets converted into steam. This steam when

available on earth’s surface at specific places can be used to run steam
turbines, and thereby generate electricity. Not much has been achieved in

tapping geothermal energy so far. In India, in Ladakh area, feasibility study
for construction of a 1 MW power station has been made. Geothermal means

heat from the earth’s interior.
Geothermal energy is generated in the earth’s core about 6400 km below

the surface of the earth. Temperatures higher than the temperature of the sun
is produced in the core of the earth by slow decay of radioactive particles.
The centre of the earth is of solid iron core and its outer is made of very

hot melted rock called magma. The magma is surrounded by rock and magma
which is also called mantle. The crust is the outermost layer of the earth. The

crust forms the land and ocean floors. See Fig. 13.5.
The crust on land area is about 25 to 55 km thick and on oceans 5 to 8 km
thick.

Inside the earth the rocks and water absorb heat from the magma. When
magma comes closer to the surface it heats up the water trapped in porous

rocks or the water running along fractured rocky areas. Such naturally formed
hydrothermal resource is called a geothermal reservoir.

Electricity generation in power plants requires steam at very high
temperature.