[Power] Haiti power questions

[scott at solarnetone.org]

Hi Richard,

A couple of points inline...

On Thu, 2 Dec 2010, Richard A. Smith wrote:

>
> Updated Chart.
>
> XO	 AC
> --	 --
> 4  W	  6   W
> 5  W	  7.5 W
> 6  W      9   W
> 7  W     10   W
> 8  W	 11   W
> 9  W	 12.4 W
> 17 W     23.5 W

Here we area showing a waste to heat of 30-35% of our power in a 
conversion step not always necessary.

>
>> Are these numbers appropriate for both power-grid systems and solar
>> to marine battery systems?
>
> If you are on a solar power set then there is one more set of efficiency
> numbers you have to factor in.

I agree with this part.

> Thats the eff% of the AC inverter.
> Typically those are 90% or more.  That means that you should take all
> the numbers above and divide them by .9 if you are on solar.  Thats the
> juice that your batteries will have to provide.

I disagree with this part.  There is no need to run the XO load through an 
AC inverter, and incur the additional waste therein, on top of the wall 
wart conversion waste.  We have no real utility for switching to 
alternating current in this application, then back down to DC.  The XO's 
have regulated power supplies.  Voltage swings will not effect them so 
much, so we only need a charge controller and battery between the XO and 
the solar panels, assuming the voltage range is correct... nominal 12V 
panels.


> The concern with generators is the power factor.  Generators are
> specified at a power factor of .8 . That's a good number to use if you
> are powering a house.
>
> Switching power supplies however don't behave nicely.  They are
> non-linear in their operation so they don't map well on to the
> "standard" power factor estimate.

One could always correct the power factor to the load with a 
tuned capacitor bank.

Cheers,
Scott