The temperature on the surface of the earth is relatively cool compared to the temperature of the rest of the planet. Heat can be obtained directly from the Earth from a shaft as shallow as 100 feet (30 metres). The deeper one digs, the more heat one encounters, and technologies such as heat exchangers and heat pumps can convert the heat from beneath the surface of the earth into usable energy. When this energy takes the form of hot water, steam or hot compressed air, it can be used to produce electricity in the exact same fashion as energy produced by steam turbines.