12 volts electrical systems?
Just wondering the other day:
Wouldn't it make sense to start having 12 volts (or 24 volts for that matter) circuitry in a household / office these days.
I mean: I just started noticing that something close to 70% of the electrical equipment I have, needs a transformer (either external or internal) to convert 220 volts (here in europe) to something between 3 and 12 volts.
And these transformers seems to eat electricity even when the machine connected to it is turned of, since they always seem to be warm.
Wouldn't it make sense to have one high-quality centralized transformer and get rid of all the other small ones (saving a few $ on every machine you buy).
Ofcourse, something like this only makes sense if the industry follows up on it by offering low voltage equipment.
I mean: yesterday I was in another one of these typical server-rooms, where the computers (old and new) were just stacked on top of eachother. Each and everyone of these machines had a transformer (each worth a few $$$) and -like always- there's a huge fan trying to cool the transformer. So basically something like 50% of the heat in that room was generated by these transformers, and also 50% of the noise. At the seem time, they need a huge airco system to try and cool the place, again eating electricity and generating noise.
I can only see advantages, if it would be followed by a large community: less cables, less equipment, less electricity consumption, less heat production, less resources waisted, less money waisted...
what's your idea?
Wouldn't it make sense to start having 12 volts (or 24 volts for that matter) circuitry in a household / office these days.
I mean: I just started noticing that something close to 70% of the electrical equipment I have, needs a transformer (either external or internal) to convert 220 volts (here in europe) to something between 3 and 12 volts.
And these transformers seems to eat electricity even when the machine connected to it is turned of, since they always seem to be warm.
Wouldn't it make sense to have one high-quality centralized transformer and get rid of all the other small ones (saving a few $ on every machine you buy).
Ofcourse, something like this only makes sense if the industry follows up on it by offering low voltage equipment.
I mean: yesterday I was in another one of these typical server-rooms, where the computers (old and new) were just stacked on top of eachother. Each and everyone of these machines had a transformer (each worth a few $$$) and -like always- there's a huge fan trying to cool the transformer. So basically something like 50% of the heat in that room was generated by these transformers, and also 50% of the noise. At the seem time, they need a huge airco system to try and cool the place, again eating electricity and generating noise.
I can only see advantages, if it would be followed by a large community: less cables, less equipment, less electricity consumption, less heat production, less resources waisted, less money waisted...
what's your idea?
Comments
V=I*R (Ohm's Law)
P=I*V (P=I^2*R)
The first thing to notice is that Power loss (power lost in a wire due to its resistance) is proportional to the square of the current. This is the reason that power is transmitted from the power plant at very high voltage--10's of thousands of volts. For the same amount of Power, a high voltage means you need less current (P=I*V). Because transmission lines have resistance, the higher the current, the more power that would be lost. This is a big deal, since power loss goes up with the *square* of the current. For this reason, power companies will transmit power as high as they can safely, and take it down to 120V only right at your block.
The second thing to notice--as was also mentioned above--is that to get a certain amount of power, you need more current if you provide less voltage.
So: let's say you have a 100A service to your house (like I do, as my house is 70 years old). Assume I'm only talking about one phase, the power provided to my house is P=100A*120V (120V=I'm a yank). That's 12,000 Watts. Now, let's assume we converted that with a transformer to 12 V. Now, instead of 100A, after the transformer we have I=12,000W/12V=1000A coursing through those wires if I used my full 12,000W. First, that's one honkin' bigazz transformer to handle that kind of conversion. secondly, that nice 12AWG wire (if you're lucky--many people have 14AWG which is smaller) you have running through your house can only handle about 23A. That means that, at 12V, you can only have a 275W load at the end: three 100W light bulbs and you're overloading the circuit. So, you'd likely need a single wire to each outlet, (rather than one wire to 4 or 5 outlets as is typical) so that's much more wiring for you to pay the Electrician to do! Btw... if you have AWG14 wire, you're limited to 192W.
Ok, so now let's take a look at what we're wasting by using low-voltage wiring. Say you need 300W for your Dell. At 120V, this is 2.5A. 12AWG wire has a resistance of ~1.58 Ohms/Km... so assume we have 100M of wire from the transformer at the street and your Dell. That means the power lost is P=(2.5^2)*0.158=0.987W. So, we loose a Watt. Not too much waste. At 12V, however, we'd need 25A to power the Dell, so now the power loss in the wire is P=(25^2)*0.158=98.75W. Whoa... almost 100W is lost in the wiring alone. Oh, and that's above the capacity of 12AWG wire, so you'd need 10AWG, which is very heavy and hard to work with. Even if we do the conversion in the house and have only, say 10M of wire, the loss is still 6W--and that's just for one computer--and remember that this only takes into account wire resistance: every time you wire-nut two wires together in a junction box, you're adding more resistance, not to mention the plug contacts, etc., so the losses are even higher.
Yes, EEs, I am oversimplyfing this somewhat, but there are some fun lessons in here. Why does the power company put a big transformer near almost every house? If they transmitted 120V throughtout a neighborhood, they'd be losing a tremendous amount of power due to wire losses: Transmitting high voltage, and only stepping it down right where you need it is much more efficient. (Transformers are one of the most efficient devices around, so lots of conversions using them wastes nearly nothing).
For more trivia, do some research of how Edison, who espoused DC transmission, was beaten out by Westinghouse (with much help from Tesla) with his AC system. Here's a hint: you can't step down DC current with a simple transformer!
hope this helps!
Originally posted by Fawkes
That's a very good question; the answer lies in Ohm's Law--the relationship between Current (I), Voltage (V), Resistance (R) and Power (P):
V=I*R (Ohm's Law)
P=I*V (P=I^2*R)
hope this helps!
hey, thanks Fawkes...
I think i got the big picture.
I'll read through it again (4 or 5 times) to get the details...
but that all seems to make sense!
tnx
b.
Originally posted by Fawkes
For more trivia, do some research of how Edison, who espoused DC transmission, was beaten out by Westinghouse (with much help from Tesla) with his AC system. Here's a hint: you can't step down DC current with a simple transformer!
That wacky Tesla, I tell ya.
Any ways, what fun would DC be, if you can't hear transformers popping in the summer, when everybody kicks on their air conditioners? It's funny, that is, if you have your computer connected to a UPS when that happens.