[GreenKeys] How much juice from a solar array?

[epvgk at limpoc.com]

On Sun, Sep 18, 2016 at 01:43:13PM -0700, Richard Knoppow wrote:
>    The link to Wikipedia includes some storage techniques. Evidently
> batteries can be used as in a UPS system.

I have a set of six panels on my roof. They charge a 400AH bank of 12v lead-acid 
batteries via a charge controller. Going by the wattage ratings on the panel 
nameplates, the rated power output is 700 watts total; this would be what you'd
get with equatorial direct sunlight at a temperature of 20C, which doesn't happen
unless you air condition your panels. In real life, in full San Francisco summer
sun at noon they produce maybe 400W peak. Practically speaking considering
cloudy days, hours of sunlight, inverters, etc, it's sufficient to power a very 
small load 24/7. 

I basically just use the panels to keep the batteries float charged, and use it
as a big UPS for the computers and things that are always running here. In the
summer on sunny days I'll sometimes switch the loads over so they're powered
by solar while the sun is shining, this is a load of about 16A at 13.2V for 
about 6 or so hours until panel output drops enough that it's drawing off the
batteries again... 

Just a practical example....

eric

> 
> On 9/18/2016 1:35 PM, Jones, Douglas W wrote:
> >From: tony.podrasky [tony.podrasky at gmail.com]  Sunday, September 18, 2016 12:13 PM
> >>I'd say the parking lot is equal to 2 football fields.
> >>Above the entire parking lot are huge solar panels.
> >>Does anyone have an idea what kind of power that can
> >>generate?
> >
> >Guestimate  .5 KWH per square meter. per day.  Guestinmate a football field at 5000 square meters,  This gives one WalMart parking lot worth of solar cells as approximately 5000 KWH per day.
> >
> >Given that an average US household uses just under 1000 KWH/month, this is enough to power about 150 houses -- assuming you can figure out how to store the excess daylight power in order to provide power on demand when the sun is down.  I guess you need to combine the solar cells with a pumped storage power plant or some such.  (Or just focus on ofsetting the air conditioning demand, which is mostly a daytime thing).
> >
> >                Doug Jones
> >                jones at cs.uiowa.edu
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> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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