[This followup was posted to sci.electronics.design and a copy was sent
to the cited author.]
I have a small 10x10 foot room I am considering cooling with a small
12000
btu AC, but I am wondering if it's possible to set this up to be powered
by
solar? The AC would not be run continuously, just long enough to cool
the
room off for sleeping, maybe 2 hours per day. I'm thinking a car battery
with an inverter and the battery charged by solar cells, but I don't know
if
this would work or even how to begin. I also want to keep this as low
cost
as possible and stick with a simple design that works.
Any suggestions would be appreciated.
Thanks,
AA
Some considerations, The 12000 BTU AC unit listed here:
http://www.lg.com/us/air-conditioners/lg-L1210ER-window-air-conditioner
..shows that it has a rating of 115VAC/60Hz with a draw of 10.2 Amps.
They also quote a rating of 1110 Watts.
If you were to use an inverter such as the following:
http://www.donrowe.com/inverters/sw1220.html
..the "optimum" efficiency is listed at ~90%. It would be more likely
that you may see 85% efficiency. That would take an input power of
1110 Watts / 0.85 = 1306 Watts.
Converting the wattage requirement to Amps at a nominal 12VDC would be
1306W / 12V ~= 110 Amps. This amperage delivered for the two hours that
you specified is 220 AmpHour.
A possible battery may be the Trojan model T-145 shown in this brochure
on page 11 of the PDF. The quoted 5-Hr rate is 215 AH.
http://www.trojanbatteryre.com/PDF/TRJN0159_RESeriesColl.pdf
To re-charge the battery from a solar array will require an array
capable of restoring the 220 AmpHour of energy during one summy day
period of time.
The solar panel showen here:
http://www.saferwholesale.com/High-Quality-280-Watt-Solar-Panel-p/dsp-
280_watt_panel.htm
..is good for 280 Watts on a good sunny day. One could estimate that you
have say 8 hours of sunlight on days when you would like the air
conditioner to function. Also let us guess at solar battery charger
efficiency of 85%. Some simple math shows that:
(1306W / 0.85) / 8 hr = 192
It looks like one of the above panels could keep your battery charged.
Two panels would give you a nice extra capacity in case you wanted to
swipe some system power for something else besides the AC unit.
--
Michael Karas
Carousel Design Solutions
http://www.carousel-design.com