Thomas Alva Edison holds 1093 patents on his inventions, which include such inventions as the incandescent light bulb, the phonograph, and direct current (DC). The latter being one of the most important and influential inventions since it was the first current to be invented. However, like any invention, it got its competition, this time, in the form of Nikola Tesla’s alternating current (AC). The war of currents between Thomas Edison’s direct DC and Nikola Tesla’s AC forever changed electricity and the way mankind lives.
In order to be able to develop a successful incandescent lightbulb, Edison, had to first develop an entire electrical system, which he modeled after the gas lighting systems used in large cities. At the time, gas systems usually included underground conductors, central stations lamp fixtures, and meters. In addition to all of this, Edison also had to create an electrical generator and the network it powered. And so, Edison developed DC, an electrical flow that runs continuously in one direction. DC can be achieved electrochemically by fuel cells and batteries or electromechanically by specific types of generators. It is also possible to produce it using photovoltaic devices. And so Edison created a DC system which was most efficient in very populous cities and for secluded plants generating power for single buildings. The DC system was more efficient and economical within a square mile of its central station. Edison’s DC was, at the start of the electricity industry, the standard in the United States for providing electricity since DC not only work very well with incandescent lamps, but was also able to be used directly with storage batteries, providing valuable load-levelling and backup power during interruptions of generator operation. In addition to that, DC generators could be easily paralleled, allowing for cheaper operation via the use of smaller machines during periods of light load and improving overall reliability. Edison also made a meter so that customers were billed based on how much energy they consumed. The DC system however, had one big problem, the electricity lost energy as it passed through the wires, and once the wires from the generator exceeded two kilometers, there was not enough electrical energy to power a lightbulb. This meant that every customer had to be a maximum of two kilometers away from the power plant. This phenomenon was called line loss, a serious problem for Edison with no obvious solution.
Nikola Tesla, a Serbian electrical engineer arrived in America in 1884, and he brought with him the solution to Edison’s problem. Tesla was an engineer and mathematician, he understood the science of the electricity including Ohm’s law and Jules law, mathematical descriptions of the relationship between voltage, current, resistance and power. Jules law revealed Edison’s problem, the simple formula, shows that the power lost when current flows in a wire is equal to the resistance of the wire times the current squared. Most of the power loss becomes heat, the wire becomes hot. The conductor was one factor in line loss, but current affected line loss exponentially, reducing current without reducing available power would solve the problem. Edison knew that higher voltages and lower currents would resolve the line loss problem, but high voltages were dangerous, there had already been some deaths when experimenting with this solution. It was not possible to safely deliver electricity at a thousand volts or more into homes. The solution that Tesla ended up proposing, a solution that was rejected by Edison, was to abandon DC, and develop an electrical grid using AC. Unlike DC, AC doesn’t flow constantly in one direction, it changes direction surging back and forth. AC could be easily produced with a special type of generator and has some very interesting properties. The surging back and forth motion of the current produces electromagnetic radiation that can induce current flow in adjacent but unconnected conductors. Tesla understood this radiation and perfected a device capable of changing voltage and current in an electrical system, the transformer. This changed everything, suddenly it was possible to deliver electricity hundreds of kilometers using high voltage low current transmission, below current reduced line losses dramatically. The wires carrying the high voltage were suspended on towers at a safe height. The final step in this solution occurred when a step down transformer converted the electricity back to a less dangerous low voltage with higher current for use in the homes and industries of the community. The relatively short distance from the transformer to the homes meant that line loss from the higher current was minimized, Tesla had found a solution to Edison’s line loss problem.
Edison realized he had a problem, his DC systems were in trouble. A company by the name Westinghouse Electric, owned and founded by the American entrepreneur and engineer George Westinghouse, had acquired various of Tesla’s patents, and they intended to use them to distribute electricity. Edison started a rather bizarre campaign to discourage the use of AC, which included the spread of false information on AC accidents resulting in death, publicly killing stray animals, and lobbying against the use of AC in state legislatures. Edison also attempted to make the term “Westinghoused” a popular term for being electrocuted. Although Edison stood against capital punishment, his strong desire to discredit AC led to the invention of the electric chair. Harold P. Brown, who was secretly paid by Edison, built the first electric chair for the state of New York to promote the idea that AC was deadlier than DC.
The Chicago World’s Fair, also commonly referred to as the World’s Columbian Exposition, took place in 1893 at the height of the war. This fair was held in Chicago to celebrate the 400th anniversary of Christopher Columbus’s arrival at the new world back in 1492. General Electric bid to electrify the fair using Edison’s DC for $554,000 but was underbid by George Westinghouse who bid to electrify the fair using Tesla’s AC for only $399,000. Although no profit was made by Westinghouse Electric, they had demonstrated that AC was safe and effective. This led them to getting a contract at the end of that year from the Niagara Falls Power Company to build an AC power station in Niagara Falls to generate power. There were some skeptics who doubted that the falls were able to power all of Buffalo, however Tesla believed it could not only power Buffalo, but all of the eastern United States. On November 16, 1986, electrical power was transmitted to Buffalo from the hydroelectric generators at Niagara Falls. The generators, built by Westinghouse Electric using Tesla’s AC system, had nameplates which bore Tesla’s name. It was pretty clear by now, who had won the war of currents, General Electric switched over to working with AC and soon after AC was standard in the United States.
Most people don’t have to look further than their neighborhood to see Tesla’s AC in action. Transformers are a common sight and most people pass by them every day, converting very dangerous thousands of volts on the supply lines to less dangerous a hundred and twenty volts for it to be used in homes. AC electrical grids cover the globe delivering power from a multitude of sources through an interconnected network of transmission lines and transformers. It would appear to most that AC had completely obliterated, however DC has been making somewhat of a comeback in recent years. Although today’s electricity is still very predominantly AC powered, computers, DC is still used and is also part of most people’s daily lives. DC is still common in electronics including integrated circuits, high power transmitters, computers, vehicle starting, and ignition systems. DC is also used in hybrid and electric cars, which is a very fast growing business, batteries, and in telephone networks. There are also now methods of converting DC to higher and lower voltages. Since DC is more stable, companies are trying to find ways of using high voltage direct current (HVDC) to transport electricity through long distances with less electricity loss.