[Power] Haiti power questions

[scott at solarnetone.org]

Hi Tony,

On Sun, 5 Dec 2010, forster at ozonline.com.au wrote:

> Scott
>
>> Full charge for XO1 measured at 156 minutes at 7.75 amps DC, but the voltage was a bit low
>
> sorry I meant 0.775A

That must be continuous current draw then.  I though you gave me a number 
for total current used during that period.  Sorry, I should have read your 
linked description of the experiment.

>
>>
>> So that gives us, @12V, 93Wh per XO delivered over a period of 2.6h, or
>> 35.77Wh per XO per hour, to achieve a full charge on the XO.
>
> 9.3 Wh per hr or 24.2Wh per charge?
>

That sounds right if you drew .775A continuously for 2.6h.


>> Our total load of 50 XO's for 2.6h is 4650 Wh.
> 1209 Wh?

Yep.

>> We must deliver 1788.5Wh per hour for the 2.6h charging period,
>
> 465W?

Yep.

>
> assuming
>> all 50 XO's a) started in a completely discharged state and b)
>> were connected and charging simultaneously.  The latter is tough on your
>> batteries.  If the school day is 6 hours, and two "shifts" of student
>> charging can be accomplished, then the LA batteries will last MUCH longer,
>> and our wiring can get much smaller.
>>
>> According to the wunderground.com solar calculator:
>> http://www.wunderground.com/calculators/solar.html
>>
>> a hypothetical deployment of 1.4kW of solar panels in Matelgate, Haiti
>> would produce an annual average of 7.3kWh generated per day, with a
>> december minimum of 6.44kWh/day being collected. Similarly,
>> 1400Ah of battery will provide 3 days of backup.  I would consider these
>> to be bare minimums for a system of this scale.
>
> 4 hrs per day equivalent is a good rule of thumb

I would guesstimate a system for the corrected load at 350-400W worth of 
panels, 400Ah worth of battery, and you shouild not need any cabling 
larger than #4 AWG, although there will be segments where dual #4 runs 
would be advisable, due to the short time period in which you will be 
drawing the current.  A single charge controller should suffice for this 
configuration as well.


Cheers,
Scott

>
>>
>> Apart from the panels, other components include combiner boxes, where each
>> panel is individually breakered, a few charge controllers in parallel, a
>> main breaker enclosure with busbars, breakers, lightning suppression, etc,
>> batteries of course, all the cabling and interconnects, and some output
>> bus bars with terminations that the XO's can be connected to.
>>
>> Cheers,
>> Scott
>>
>>>
>>> Done with an XO1.5 running Turtle Art
>>> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Measuring_DC_Amps
>>>
>>> Tony
>>> _______________________________________________
>>> Power mailing list
>>> Power at lists.laptop.org
>>> http://lists.laptop.org/listinfo/power
>>>
>>
>> _____________________________________________________
>> This mail has been virus scanned by Australia On Line
>> see http://www.australiaonline.net.au/mailscanning
>
>