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Posted by j on February 16, 2012, 12:53 pm
 
   Having previously had no interest in PV solar, I am now somewhat
intrigued.

I've noticed a huge number of tabbed and untabbed cells. Some that are
advertized as almost whole for prices under $.50/W. Some that are grade
A whole for ~$.70/W.

I am not sure what you do with these. Does it need glazing over it?

I've got a couple of potential uses. One is that I know of a few people
living off grid, who struggle with simple things like getting cell
phones charged. Or recharging AA and AAA batteries. Voltage input
tolerance for 12V source chargers is wide.

The other is that I have a location here where I was going to set up
domestic hot water, I have about 120SF of such. Solar could run the
pumps, although low power DC pumps are pricey.

But it seems a bit crazy, but it is little money crazy. Throwing a
couple hundred bucks at crazy is not the same as throwing a couple thousand.

Thoughts?

   Jeff

Posted by Winston on February 16, 2012, 2:53 pm
 
j wrote:

advertized as almost whole for prices under

Leave them on the shelf until prices become less insane.  :)

off grid, who struggle with simple things

input tolerance for 12V source chargers is

hot water, I have about 120SF of such.

hundred bucks at crazy is not the same as

You are headed in the right direction.

Advise do the arithmetic and base your decision on the
total situation, sans any regard to the romance of alternative
energy.  PV is still about 10x too expensive for those
of us who enjoy grid power *for most applications*.

I have three little 10W PV panels on the house right now.
They power fans that exhaust hot air out of the attic
and garage. I have about $50 in them, so they were an
extravagance. However, they have made a night-and-day
difference in my comfort and will extend the useful life
of my hideously expensive roof by several years.
I also like the fact that they will continue to work
during a summer power blackout.

The low hanging 'solar fruit' is space heating and
domestic hot water.  Payback for those systems is much
quicker than that of PV, which will not 'pay back' at
all, for most folks.

--Winston

Posted by danny burstein on February 16, 2012, 3:00 pm
 

hot water, I have about 120SF of such.

That's where a trip to your local auto junkyard comes in handy.

Plenty of 12 VDC (and you might even find one of the 24 V ones
 used on some trucks) water pumps around. Cheap enough to
 replace them every couple of years...

--
_____________________________________________________
Knowledge may be power, but communications is the key
             dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

Posted by Jim Wilkins on February 16, 2012, 3:06 pm
 
I set up a Harbor Freight solar kit and a batch-type solar water heater to
experiment.
http://www.harborfreight.com/45-watt-solar-panel-kit-90599.html

The water heater is a tank at ground level with no external plumbing, fill
it with a hose through a backflow preventer and carry hot water to the
washing machine in a bucket. In addition to being much cheaper to build this
way it causes no damage when it leaks and it can't contaminate the household
water supply.

Both are at best only marginally worth the cost and effort. The water heater
saved about 5-7 cents of electricity per laundry load, the difference
between meter readings before and after. It is nice to have free hot water
in the garden hose to wash sap and bird crap off the car. The solar panels
produced only enough power to run this laptop during a week-long power
outage. I still needed a generator to run the washing machine.

I seriously doubt that the electricity saved would ever make up for wear on
the 12V batteries or the gasoline to hunt down cheap second-hand ones, even
if the solar panels were free. A 105A-H 12V battery that cost $0 holds less
than $.20 worth of grid electricity. That's over 400 full discharge cycles
to break even.

The controller in my HF kit cuts out at 14.2V, a reasonable setting to fully
charge a battery without damage if you don't leave it connected too long.
You could use it to maintain the batteries on unused equipment over the
winter.

For experimenters the controller needs a charging current meter to aim the
panels and show you the output.
http://www.futurlec.com/Panel_Meters.shtml
http://www.adafruit.com/products/574

jsw



Posted by news on February 16, 2012, 3:44 pm
 On Thu, 16 Feb 2012 10:06:38 -0500, "Jim Wilkins"


Simpler than the digital ammeters that require power - an analog meter
that is inserted in the line from the solar panels:
http://www.ebay.com/itm/DC-10A-AMP-Analog-Current-Panel-Meter-Ammeter-0-10A-SHUNT-/250995579619?pt=LH_DefaultDomain_0&hash=item3a70809ae3

And it's $.45US includng shipping.

Is it 1% accuracy?  Unlikely, but in this qpplication absolute
accuracy isn't important -  you're just looking for the maximum
reading as you adjust the position of the solar panel(s).

John

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