Geothermal Energy–What’s Its Source?

What is the source of geothermal energy? According to Terrestial Energy, written by William Tucker, if you drill a 1000 feet (305 meters) deep hole, the temperature at the bottom of the hole is 16F (10C) higher than at the top.  Tucker says that the average temperature of the ground is 54F (11C) so the bottom of that hole would be 70F.

The Homestake Gold mine in Lead SD, discovered in 1876, produced 40 million ounces of gold and 9 million ounces of silver. At the time of its closure in 2002, the mine was more than 8000 feet below the surface   Based on Tucker’s formula, the temperature at the 8000 foot level would be around 180F unless cooling air was introduced. .  At one time, one of my relatives (by marriage) was the engineer responsible for keeping the temperature in the mine at a level that would allow people to work.  And his description of what was needed to do that was pretty impressive.

Tucker goes on to say: “At 80 miles down we hit the Mohorovicic Discontinuity, discovered by Yugoslav seismologist Andrija Mohorovicic in 1909. At this point the temperature reaches 900o C and rock turns to liquid “magma.” At 1500 miles deep the temperature rises to 3700o C and another discontinuity – the Gutenberg – marks the place where molten rock becomes pure iron and nickel. Below that tremendous pressures turn the iron core solid once again and temperatures reaching 7,000o C – hotter than the surface of the sun.”

He explains that the source of this heat energy as follows: “Some of it is due to gravitational forces. As the earth is pulled inward, some of this force is translated into heat. Another portion is residual heat from the earth’s formation. According to the commonly accepted theory, originally proposed by Immanuel Kant, the solar system precipitated out of a huge swirling dust cloud, where particles kept colliding with each other until they agglomerated into the sun and the planets.

In the later stages, this involved huge collisions among very large objects. These impacts generate large amounts of heat, some of which still remains in the earth’s core. Together gravitational forces and residual heat probably account for about 40 percent of the earth’s temperature – the exact figure has still not been determined.

The other half of the earth’s heat, however, comes from a remarkable diminutive source – the slow breakdown of two of the 90 elements, uranium and thorium. With 92 protons, uranium is the largest natural atom, while thorium (90) is the third largest. Because of their size, they are unstable, meaning they are “radioactive.”

The internal “binding energy” that overrides the mutual repulsion among positively charged protons is occasionally overcome itself. This releases large quantities of energy, which sets subatomic particles in motion, creating large amounts of heat. Incredibly, the slow breakdown of these two radioactive elements, uranium and thorium, is enough to raise the earth’s internal temperature beyond the level of the surface of the sun.”

Tucker draws some conclusions from this when he says: “Why don’t we just take the source of that heat – the uranium or thorium – bring it to the surface, and reproduce or even accelerate the process that produces this heat in a controlled environment?

This is what we do in a “nuclear reactor.”  “A nuclear reactor is nothing more than terrestrial energy brought to the surface. There is nothing sinful or diabolical about it. We are not defying the laws of nature. Rather, we are working with a process that already takes place in nature.”

h/t Master Resource


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