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The War of the Currents: AC vs. DC Power

November 20, 2013 - 3:52pm

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Electrical transmission lines cross a snow-covered field in Dallas Dam, Oregon. | Photo courtesy of the Energy Department Flickr page.

Electrical transmission lines cross a snow-covered field in Dallas Dam, Oregon. | Photo courtesy of the Energy Department Flickr page.

This week on Energy.gov, we’re revisiting the storied rivalry between two of history’s most important energy-related inventors and engineers: Thomas Edison and Nikola Tesla. Check back each day to learn more about their lives, their inventions and how their contributions are still impacting the way we use energy today. Support your favorite with the hashtags #teamedison and #teamtesla on social media, or cast your vote on our website. And be sure to submit questions about the inventors for our live Google+ Hangout with Tesla and Edison experts, happening Thursday, Nov. 21, at 12:30 p.m. ET.

Starting in the late 1880s, Thomas Edison and Nikola Tesla were embroiled in a battle now known as the War of the Currents.

Edison developed direct current -- current that runs continually in a single direction, like in a battery or a fuel cell. During the early years of electricity, direct current (shorthanded as DC) was the standard in the U.S.

But there was one problem. Direct current is not easily converted to higher or lower voltages.

Tesla believed that alternating current (or AC) was the solution to this problem. Alternating current reverses direction a certain number of times per second -- 60 in the U.S. -- and can be converted to different voltages relatively easily using a transformer.

Edison, not wanting to lose the royalties he was earning from his direct current patents, began a campaign to discredit alternating current. He spread misinformation saying that alternating current was more dangerous, even going so far as to publicly electrocute stray animals using alternating current to prove his point.

The Chicago World’s Fair -- also known as the World’s Columbian Exposition -- took place in 1893, at the height of the Current War.

General Electric bid to electrify the fair using Edison’s direct current for $554,000, but lost to George Westinghouse, who said he could power the fair for only $399,000 using Tesla’s alternating current.

That same year, the Niagara Falls Power Company decided to award Westinghouse -- who had licensed Tesla’s polyphase AC induction motor patent -- the contract to generate power from Niagara Falls. Although some doubted that the falls could power all of Buffalo, New York, Tesla was convinced it could power not only Buffalo, but also the entire Eastern United States.

On Nov. 16, 1896, Buffalo was lit up by the alternating current from Niagara Falls. By this time General Electric had decided to jump on the alternating current train, too.

It would appear that alternating current had all but obliterated direct current, but in recent years direct current has seen a bit of a renaissance.

Today our electricity is still predominantly powered by alternating current, but computers, LEDs, solar cells and electric vehicles all run on DC power. And methods are now available for converting direct current to higher and lower voltages. Since direct current is more stable, companies are finding ways of using high voltage direct current (HVDC) to transport electricity long distances with less electricity loss.

So it appears the War of the Currents may not be over yet. But instead of continuing in a heated AC vs. DC battle, it looks like the two currents will end up working parallel to each other in a sort of hybrid armistice.

And none of that would be possible without the genius of both Tesla and Edison.

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