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anagami
Light Sweet Crude
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Location: Sudavasa Abodes
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 Posted: Thu May 01, 2008 11:59 pm Post subject: AC/DC |
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I've not read much on AC/DC conversion, on wikipedia there aren't many percentages of energy lost due to ineffiency in conversion. But there are cases where efficiency can be made easily.
I'm thinking mostly of:
1) an UPS that converts AC to DC for a battery, and then to AC, where an electronic product will convert again to DC. What is the inefficiency penalty of converting twice energy?
2) Basically the same but with a house with solar or wind energy. From DC to AC cabling and from AC to DC for electronic products.
In both cases, if only DC energy is used, the energy lost in each conversion is conserved.
To ad to this, as far as I know, AC wastes energy in heat instead of electricity (the "power bricks"). But I think that is also due to AC to DC conversion.
Not to turn this into cornucopian wishful thinking, but on a talk with a friend (...I think he is cornucopian), there was the proposal of using light as it is for energy source. AFAIK, light transmission has only 1 way of distribution, and standarizing on light distribution over fiber as energy source... or using low to medium voltage products that just need light (and have batteries for the night) may be quite nice.
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SolarDave
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Joined: May 19, 2005
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| Posted: Fri May 02, 2008 12:34 am Post subject: Re: AC/DC |
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This is by no means 100% accurate, but it follows the principles you have listed:
Circuit Configuration Application
Check the box "Show Efficiencies" and then play around. You can assemble both a DC TV and an AC TV with all the required "transformation" steps as you have described and see how that affects end-to-end efficiency.
I built this and I used actual measurements I had made on a range of equipment as the basis for the calculations. HOWEVER, there can still be wide variations between different brands of TV's, inverters, voltage regulators, etc etc etc. Nevertheless, generally speaking I believe this will give you some good basic data, and you can experiment a little.
SolarDave
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SolarDave
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| Posted: Fri May 02, 2008 12:38 am Post subject: Re: AC/DC |
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Also - re: using light - it's not very efficient to make light or to turn it back into electricity. Both are worse efficiency-wise than even a cheap inverter (DC->AC).
If we could make light efficiently, we would replace all our lightbulbs and cut lighting energy in half or better.
If we could convert light into electricity efficiently, a 3 KW Solar array would be three feet wide and nine feet long. Right now they are about 4-5 times that large do to the inefficiency of the conversion.
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smallpoxgirl
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Joined: Nov 08, 2004
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| Posted: Fri May 02, 2008 12:48 am Post subject: Re: AC/DC |
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| zensui wrote: | | In both cases, if only DC energy is used, the energy lost in each conversion is conserved. |
There certainly is loss in AC/DC conversion. The problem with straight DC is that it is generally 12 volts or sometimes 24. AC is 120v at least.
Electricity lost in wiring supplying a given load goes up quite dramatically as the voltage decreases.
Electrical codes for example a 5% wiring loss would be a common limit. For 120v, that would be 6 volts. Say you wanted to supply a 1000 watt tool, 100 feet away. At 120v, that would be 8.3 amps. So that's a wiring resistance of 0.72 ohms/100'. That's an 18 gauge wire.
By comparison....at 12volts, 5% would be 0.6 volts. The tool would require 83 amps, so the resistance has to be below 0.0072 ohms/100'. That's 000 gauge wire.
100' of 18/3 wire is about $16.
100' of 000/3 wire is about $1500.
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anagami
Light Sweet Crude
Joined: Jul 26, 2006
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Location: Sudavasa Abodes
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| Posted: Fri May 02, 2008 11:21 am Post subject: Re: AC/DC |
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Thanks for the information 
| SolarDave wrote: | Also - re: using light - it's not very efficient to make light or to turn it back into electricity. Both are worse efficiency-wise than even a cheap inverter (DC->AC).
(...) |
I was refering to using light as energy instead of electricity.
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Troyboy1208
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Joined: Apr 26, 2006
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Location: Orlando FL
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| Posted: Fri May 02, 2008 7:29 pm Post subject: Re: AC/DC |
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| What a great Band! Woo hoo |
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SolarDave
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Joined: May 19, 2005
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| Posted: Fri May 02, 2008 8:55 pm Post subject: Re: AC/DC |
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| zensui wrote: | Thanks for the information
| SolarDave wrote: | Also - re: using light - it's not very efficient to make light or to turn it back into electricity. Both are worse efficiency-wise than even a cheap inverter (DC->AC).
(...) |
I was refering to using light as energy instead of electricity. |
Sorry, I misunderstood your original question.
Did you mean something like this?
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