We can not depend on the limited reserves of fossil fuels for the sources of energy. The fossil fuels reserves are expected to last for nearly 100 years.
There is a huge source of geothermal energy in our earth. It is environment friendly and renewable sources of energy. To overcome the energy crisis, it can be used to produce electricity.
Principle (for high temperature):-
Underground water forms steam when it comes in contact with hot rocks. The pressure of steam becomes very high. It is taken out through pipe from inside the earth. The stream is used to rotate the turbine to produce electrical energy.
Principle (for low temperature) :-
When underground hot water comes through rocks on the surface of the earth, it forms hot spring. Its temperature is lower than that of the underground hot water. Organic liquid isopentane is kept in a boiler and heated by the heat of the hot spring. The boiling point of isopentane is 280C (approx). The vapour of isopentane is allowed to fall on the turbine with high pressure .In this way, dynamo connected to turbine produces electrical energy.