Advantages and Opportunities in Geothermal Energy
Mary H. Dickson and Mario Fanelli: “Heat is a form of energy and geothermal energy is, literally, the heat contained within the Earth that generates geological phenomena on a planetary scale. ‘Geothermal energy' is often used nowadays, however, to indicate that part of the Earth's heat that can, or could, be recovered and exploited by man”. (Dickson & Fanelli, 2004)
Experiments with geothermal energy first began when De Gensanne performed measurements by using a thermometer in 1740 in a mine near Belfort in France (Buffon, 1778). It is expected that all modern thermal models work with the heat continually generated in many years of the long-lived radioactive isotopes of uranium (U238, U235), thorium (Th232) and potassium (K40), which are shown in the Earth (Lubimova, 1968). It was then in 1980 that it was possible to access on realistic models that demonstrated there was no equilibrium between the radiogenic heat generated in the Earth's interior and the heat dissipated into space from the Earth, and it indicated that our planet is going to be slowly cooling down. Stacey and Loper (1988) cited a heat balance from in which the total flow of heat from the Earth is approximated at 42 x 1012 W (conduction, convection and radiation).
In this sense, 8 x 1012 W come from the crust, which indicates only 2% of the total volume of the Earth, 32.3 x 1012 W come from the mantle, which indicates 82% of the total volume of the Earth, and 1.7 x 1012 W come from the core, which represent 16% of the total volume and contains no radioactive isotopes. (See Figure 1 for a sketch of the inner structure of the Earth). In terms on estimating radiogenic heat of the mantle which is 22 x 1012 W, the cooling rate of this fraction of the Earth is 10.3 x 1012 W. (Dickson & Fanelli, 2004)
Recently estimations illustrate based on a greater number of data, the total flow of heat from the Earth is about 6 percent...