Skip to Content.
Sympa Menu

homestead - Re: [Homestead] [Fwd: Re: Alternative inventory:Solar]

homestead AT lists.ibiblio.org

Subject: Homestead mailing list

List archive

Chronological Thread  
  • From: Don Bowen KI6DIU <don.bowen AT earthlink.net>
  • To: homestead AT lists.ibiblio.org
  • Subject: Re: [Homestead] [Fwd: Re: Alternative inventory:Solar]
  • Date: Tue, 25 Dec 2007 09:13:33 -0800

At 12/24/2007, you wrote:
The line losses for DC are greater than for AC.

Not the case, the current flowing in a wire does not care is it is AC or DC, it cares only for the amount of current and the amount of resistance. This is known as I squared R losses. To continue from the power formula, P=IE (power in Watts equals current in Amps times Voltage). A much more important formula is Ohms law I=ER (current in Amps = Voltage times resistance in Ohms). Substituting around yields the formula used for line losses P=I^2R (Power in Watts equals current in Amps squared times resistance in Ohms)

Wire has resistance so you can see in the above the losses rise by the square of the current. Using the 12V to 120V example. Current flow in the 12V circuit will be 10 times the current in the 120V circuit. The line loss in the above example at 12V is 1000 times line loss at 120V. Notice polarity has no input.

Many RE systems are going to 24 and even 48 volts to reduce line losses. From 12 to 24, the line losses are cut to one quarter and 48 is another 75% cut.

The advantage of AC is the ease of changing voltages. The line to your house is often 7200 Volts while to the house is 240. The transformer on the pole does this reduction easily. Your 200 Amp house hold system only needs 6 Amps to the pole so not only are line losses reduced but significantly smaller wire is needed.


Don Bowen Awl Knotted Up KI6DIU
http://www.braingarage.com




Archive powered by MHonArc 2.6.24.

Top of Page