Thomas Edison – The Ultimate Winner of The Current War

The competition between Nikolas Tesla and Thomas Edison to supply electricity to cities in the late 1880s is often called the ‘War of Currents’, as this battle ultimately decided what type of current became the standard for the generation of electricity today. The battle between Edison’s direct current (DC) and Tesla’s alternating current was initially won by Tesla, as his method was easier to step up and down between high and low voltages and was more easily transmitted over longer distances. ‘War of Currents’, however, is far from over as each method has both advantages and disadvantages.

Direct current was first produced in 1800 by the Italian physicist Alessandro Volta, in his battery called the Voltaic pile. It is the direct flow of an electric charge through a conducting path, hence the name. A clear example of DC power is in a battery or fuel cell. In t he late 1870s and early 1880s, electricity began to be generated at power stations and was used to power street lighting running on direct current. Edison powered this industrialisation of electricity and used direct current to transmit electricity between power stations and devices that used the power. However, there were two problems: direct current could not be easily converted between higher and lower voltages and it was hard to transmit it over long distances. Tesla, who was one of Edison’s students, believed that he had the solution to this problem: alternating current instead of direct current. Alternating current is a type of current in which the electric charge periodically switches directions back and forth and is based on the principles devised by Michael Faraday in 1832. AC can be converted to different voltages relatively easily using a transformer. A simple transformer consists of two or more coils of insulated wire wound on to a laminated steel core. When a voltage is introduced to the first coil (called the primary coil), the iron core becomes magnetized. This induces a voltage in the other coil (called the secondary coil or output coil). The number of times the second coil is wound around the core of the transformer regulates the size of the voltage output.

With Tesla and Edison each having different ideas on what the future of electricity should look like, a war began. Edison was earning great royalties from his direct current patents, and therefore set out to discredit Tesla’s ideas on alternating current. He spread rumours that alternating current was more dangerous, even going so far as to publicly electrocute stray animals using alternating current to prove his point. The decisive moment in the ‘War of Currents’ took place in 1893 at the Chicago World’s Fair. Using Tesla’s alternating current, the fair could be powered for $399,000, whilst Edison’s direct current could power the fair for $554,000. In terms of cost and efficiency, Tesla’s AC was the clear choice and since then, AC has been the method of power transmission. However, both AC and DC had advantages and downfalls.

DC’s major problems were, as stated earlier, transmitting it over longer distances successfully and stepping up and down the voltage. According to Regoli (2016), to upgrade or downgrade the DC voltages requires complicated circuitry and, because the wires lose power quickly, additional circuitry is required to ‘rejuvenate’ the voltage when transmitting electrical energy over long distances. Regoli continues by explain that in contrast to DC, AC is easily transmitted over long distances and can be converted between high and low voltages using a simple transformer. However, DC current does have one very large advantage: DC power can be stored (such as in batteries) whilst AC cannot.

Although AC won The Current War in the time of Edison and Tesla, the age of semiconductors forced the return of direct current. A semiconductor a solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. The most commonly used semiconductor is silicon and is predominantly used to power electronic devices, mostly ones that functions in only two states: on and off (such as phones, computers etc). Due to modern society’s reliance on computers, tablets and other portable devices that all use semiconductors, DC has made a comeback. These devices that use semiconductors require a consistent flow of electricity and therefore rely on direct current. In AC, the voltage periodically reverses itself, and hence so does the direction of the current flow, meaning that there is an infinitesimal amount of time per period in which there is no power. This period of no power is is something that constantly power-hungry electronic devices can’t handle and hence DC is used. As well as being used in electronic devices, DC is also used in solar panels. All solar cells are based on semiconductor substrates and they generate or operate on DC power.

Today, power is relied upon for many things, and therefore having a sustainable, affordable, reliable power source is critical. To achieve this, both AC and DC work in tandem. Alternating current runs through power lines, providing the electricity we require to homes and businesses and is pushed to high voltages to overcome energy loss through resistance. When the electricity arrives at its destination, the AC voltage then is converted to DC with a rectifier to power household devices, such as lightbulbs, lamps and other appliances. However, the efficiency of rectifiers is questionable, and they are expensive. The solution to this would be to use DC instead, which would eliminate the current ‘switch’ between current transmission type before use. However, the simplicity with which AC voltages can be controlled and transported is still unmatched by simple DC, meaning that AC is still the preferred method. There is, however, a new technology that could be the solution to this problem: High Voltage Direct Current (HVDC).

When it comes to transmitting large amounts of power over long distances, HVDC is much more efficient than the conventional AC lines. HVDC lines deliver more of the power put into them than regular AC lines regardless of the distance that the electricity travels; can transmit up to 3 times more power than AC systems of equivalent voltage and whilst they are often more expensive to build, they are more cost effective in the long term in comparison to AC (Barnard, 2018). The future of electricity relies on renewables and because HVDC is able to transmit large amounts of remotely generated electricity over long distances to cities, it could play a key role in the future of electricity. Already in Brazil, HVDC is being used to transfer ‘clean energy’. According to Plas (2017), the Rio Madeira 10-gigawatt hydroelectric HVDC project transports two-thirds of the energy produced from the hydro plant in the Amazon basin across more than 1,475 miles (the world’s longest power transmission link) to 44 million residents living in the south-eastern populated areas around São Paulo. However, according to Circuit Globe, HVDC transmission is only less expensive for long distance transmission, with transmission lines needing to be at least 600kms long and underground cables needing to be at least 50kms long. Therefore, HVDC is not the solution for short distance electricity transmission.

Both AC and DC power have benefits and downfalls and both play an important role in electricity production and transmission now. The future of electricity production is in renewable energy sources, so how that electricity gets transferred from a wind a wind or solar farm to homes and businesses all around the globe is an important issue to consider. Currently, majority of high voltage electricity transmissions are done through alternating current, but the future lies in high voltage direct current. It is cheaper, more efficient and carries electricity in a form that is easily stored and used. Therefore, whilst Tesla’s AC may have initially won ‘The War of Currents’, advancements in direct current technology have proven that HVDC is the future and therefore the ultimate winner of ‘The War of Currents’ will most likely be Thomas Edison.

References

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