Design Article
AC/DC: Not just a rock band anymore
Junko Yoshida
10/2/2008 1:42 AM EDT
You'll recall that it started back when Thomas Edison promoted direct current power generation while Nikola Tesla invented a relatively simple AC induction motor and advocated a alternating current distribution system.
At the Ceatec Japan show here, Sharp showed what the company calls its "DC Eco House," a concept illustrating carbon-neutral living.
Sharp created a miniature house equipped with crystalline solar modules on its roof, generating power in DC, which can be directly distributed throughout the house to power up "the next-generation" refrigerator, air conditioner, LCD TVs and power LED lights, all featuring a DC input.
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The TDK mock-up showed a flow of energy from multiple energy sources not only to the home but throughout the home, with Home Energy Management System installed inside the home.
Both companies are advocating foregoing multiple conversions of DC-to-AC and AC-to-DC. They believe such a step will prevent energy losses by up to "several percent."
They are asking: Isn't it about time for DC power delivery systems to replace, or at least augment, the current AC distribution system " at home?
Some active discussions are already taking place in the United States to promote the use of DC power in facilities such as datacenters.
What's new at Ceatec, a Japanese consumer electronics show, is that the similar debate now includes power to the home.
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Doofus
10/2/2008 11:59 AM EDT
Reminds me of when the Swiss wanted everyone to switch to decimal time so they could sell everyone on the planet a new watch.
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b0110x
10/2/2008 3:18 PM EDT
There are health reasons too. A small percentage of the population is sensitive to AC fields, both RF and ELF. The Japanese seem to be more culturally aware of this, judging from their stringent radiation limits on consumer communication devices.
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Abarafi
10/2/2008 3:28 PM EDT
AC and AC distribution is a throwback to the first industrial revolution. First, we had big steam engines turning a main shaft to which pulleys and belts were attached to power individual machines. The fractional horsepower motor and AC distribution got rid of the steam engine and main shaft, replacing it with outlets and individual motor-driven machines. But there was still a big engine (the power plant) producing electrical energy. There was a compelling reason to go AC back then - the cost of producing the energy was a lot less than the cost of distributing it. Today, the costs of producing are going through the roof. In a world in which a lot of electrical energy is being produced, locally, via photovoltaics, wind or whatever, it makes sense to get rid of the DC-to-AC conversion process and have a DC distribution system feeding DC-ready appliances. With short runs, and high enough DC voltages, the IR losses can be kept low, and an AC-humless world can ensue.
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Chris_Gammell
10/9/2008 8:37 AM EDT
I had written about a similar idea a while back (http://chrisgammell.com/2008/06/12/can-dc-power-an-entire-home/). I am interested in the idea, but am still worried about replacing low cost AC motors with potentially more expensive DC motors (I always think of my coffee grinder). I'm sure as more devices shrink and become power conscious, the DC home model will become more feasible.
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KPL
10/11/2008 12:37 PM EDT
There will still need to be multiple voltages for long distance, intermediate, and local distribution. Even within the home or office, each appliance needs different internal voltages. Numerous DC-DC converters will be needed where we presently use AC-DC converters or transformers.
So why should DC-DC converters be inherently more efficient than AC-DC converters or transformers ?
High Voltage DC lines have been used for years. But the cost is prohibitive except for long distances, because of the cost of the terminal equipment.
Also, high power AC motors are much more economical and reliable than DC motors. Even many electric cars, like the Tesla, use AC motors.
Even if a all-DC system had advantages, any large scale conversion would be prohibitive.
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Etmax
10/12/2008 7:00 PM EDT
Let's just hope they standardise both the distribution voltage and the power sockets globally this time.
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daleinaz
12/5/2008 7:26 PM EST
DC power has issues with galvanic corrosion, ask BART in San Francisco. Also inductive spikes due to load dumps, and potential oscillation due to the negative resistance slope of DC/DC converters. Personally, I'd be happy if we could get most of the world to agree on a common ac outlet.
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