On Friday, December 1, 2017, 10:56:48 AM PST, John <[email protected]> wrote: >If you are not familiar with Tesla's theories in his later years, he explored >fantastic topics like free energy, anti-gravity, invisibility, and time >travel.
In my opinion, Tesla's main claim to fame was his recognition that the electrical grid could not possibly be implemented using DC (direct current) but had to be AC (alternating current). The simple reason for that it that even a wire, as efficient as it is for transporting electrical energy, would be inefficient if it transported (say) 120 volts more than a distance of 100 yards. There is no simple, reliable mechanism (at least, there wasn't in the late 1800's) for converting DC voltages. (the motor-generator isn't too complex, but it is only of limited reliability.) Why Edison didn't immediately understand this is baffling. There was, and is, however, an amazingly simple way to convert AC voltages: The transformer. No mechanical moving parts, and it can be used to nearly 1 million volts. That's why AC worked, and DC would never have worked. The loss of transmitting power is proportional to the square of the current: Power = I(squared) times R, where R is the resistance of the link. Thus, loss is inversely proportional to the square of the voltage. That's why today, voltages at least as high as 760KV are used over long distances. About 10 years ago, I realize the role that MCNT (metallic carbon nanotubes) will play in the future electrical grid. Despite the name, there is no "metal" in MCNTs. They are called "metallic" simply because they are seen to conduct electricity as well as common metals, like copper. But even that underestimates things:A single MCNT fiber, 1 nanometer in diameter, has a resistance of about 7600 ohms, NO MATTER HOW LONG IT IS! That is weird! But true. It's very close to the concept of superconductivity, but it will work at room temperature. A rod of copper, area 1 square centimeter, one meter long, would have a resistance of about 170 microohms. https://www.google.com/search?q=copper+resistivity&oq=copper+resistivity&aqs=chrome..69i57j0l5.4596j0j7&sourceid=chrome&ie=UTF-8 A bundle of one hundred trillion, area 1 square cm, 1 nm diameter MCNTs, each MCNT 1 meter long, would have a resistance of: 7600 ohms/(1E14), or 76 picoohms. Thus, those MCNTs would have a resistance of about 1/2,000,000 that of the copper. And if the individual MCNTs fibers were 10 meters long, the resistance of the bundle would be 1/20,000,000 that of the equivalent-sized copper rod. And so on. Why is it very important to develop a manufacturing process to make long, cheap MCNT's? There is a band of land, about 300 miles wide and over 1000 miles long, from North Dakota, South Dakoa, Nebraska, Kansas Oklahoma, and northern Texas, that has an enormous amount of wind energy. https://www.nrel.gov/gis/wind.html When you look at this map, keep in mind that the amount of extractable wind energy is proportional to the cube (third power) of the airspeed. Why not plant a million, 5-megawatt wind turbines there? The problem is that transmitting that electrical energy to places where it is needed efficiently is very difficult. The coast is 1500 miles away, in either direction. And using high voltages requires wide rights-of-way, which are very limited in availability. Using MCNT cables would allow the transmission of this power at far lower voltages (say 60,000 volts), buried by the side of small roads. Jim Bell
