Re: [pvusers] Question for "solar sizer" users

[cor_van_de_water@dolfijn.nl (Cor van de Water)]

John D'Angelo was almost right.
Rounding 3.26 up gives 4 strings of 225Ah batteries.
Each string is 4 batteries of 6 Volts, so 16 batteries in total.

However, I would approach this problem from the other side:
How *LITTLE* power do you actually need to survive a day?
This poses a challenge to your ingenuity to be clever with
power - use efficient appliances, find alternatives and in
general: reduce before opting for alternative ("preferred")
energy sources.
After you reduced your demand as much as you can, you should
size your system and add in a little extra for future growth.

This approach is much friendlier to your wallet than going for 
the big system and then find out that you don't need it all
when you live smart.

I went down from 9 to 4 kWh dayly before installing solar.
Even buying a heat-pump drier of $1000 is cheaper than 
installing the extra 8 panels or so, to generate the energy
for this single appliance. (NOTE that even on grid power,
the heat-pump drier is "investment-neutral" compared to a
regular drier + cost of electric energy difference)

Anyway, try to keep your system as small as you allow
yourself with your own level of comfort.

Hope this helps,
Kind regards from the Netherlands,
Have a great power-independence day!
Cor van de Water

> on 7/2/01 13:44, Tom Cathcart at tc@abe.msstate.edu wrote:
>  
> Tuesday, July 3, 2001 8:49
>  
> > I am a bit confused about how the number of batteries is computed in
> > "solar sizer." I have a daily AC power demand of 7.5 kWh (24 V PV
> > system, 6 V batteries, 225 rated Ah). The computed 1-day storage
> > requirement from "solar sizer" is 20 batteries (50 % draw down, 90 % of
> > rating due to temp, 90 % inverter efficiency). I don't have a clue how
> > solar sizer arrived at 20 batteries. Five strings of 4 batteries each
> > gives a rated 1125 Ah. After that, nothing that I do to get to 7.5 kWh
> > works. Any suggestions?
>  
> A 7,500 watts @ 24V DC is a daily load of 312 maps hrs per day.
> One days storage at 50% DOD is 612 AH. COnsidering that the inverter may be
> 95% efficient and the battereis themselves are  about 80% efficient
> then you have a 20% loss. So 612AH x 1.2 is 734 AH. IF you have a 225 rated
> 6 volt battery you need 4 batteries per 225 Ah. You divide 225 into 795 and
> you get 3.26. Trouble is you can't have .26 of a battry bank, so Solar sizer
> rounds up. So you need 4 battery bank hooked in series - parellel. Four 6
> volt battery per 24V @ 225AH will give you a total of 20 - 6 volt batteries.
> The solar sizer software works fine.
>  
> I hope this is clear.
>  
> --
> Sincerely,
>  
> John D'Angelo
>  
> Renewable Energy Technologies
> 877 S. Cole Dr.
> Lakewood, Colorado 80228-3021
> USA
>  
> 720-299-4254 Voice mail
> 509-562-9579 Fax
> 720-299-4254 Direct Phone Line
> Direct email: retjohnd@home.com
>  
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