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[aprssig] Special GPS

Brian B. Riley brianbr at mac.com
Tue Jul 26 14:45:29 UTC 2005


For solar PV panels a tracker is generally an exercise in ego in other words
a complete waste of time and money. The cost of a tracker to reliably
track/rotate say a rack of 8 panels is generally 2-3 times the cost of the
extra non-tracking solar panels that would supply the extra power that
tracking would gain you. The generally accepted figure is that a tracker
will gain you about 9% at the most. On a rack of 8 75 watt Siemens SP-75's
that means two extra panels at $400/each. You would be lucky to build a
tracking rack for that many panels for $800 doing it all yourself, you would
be lucky to buy such a rack for anything under $1500 unless there have been
some serious breakthroughs since I last looked at them.

Another point; Now, I didn't see the original post here but any system
involving reflective surfaces to focus additional energy to boost the
insolation from 900 watts/square meter forgets the fact that you are going
to cook the panel. I have one word on this subject, TANSTAAFL!

Back in the late 80's there was the huge "Solar One" project out in the
California desert. When the government funding ended a huge number of
surplus "quad-lams" flooded the solar market. A "quad-lam" was a four panel
ARCO unit. People bought them up like hotcakes. They were immediately
identifiable from a great distance by the brown color of these blue panels.
They had had baked into oblivion out in the California desert by the
reflective concentrators. They all died early deaths, their outputs trailing
off to under 50% of spec by  the 10-14th year of their lives. On the other
hand I have here at Wulfden Manor some Solarex MSX-60's (used without
concentrators) I bought in 1989 that are still putting out at 90-95% of
original spec.

I looked at this 'redrok' website and he seems to have done some interesting
things, but I question his figures very much. There is no way tracking can
get a 50% gain unless he is is in some physically constraining arrangement
that reduces his available sunlight somehow. As I said above in a free open
area the concensus opinion is 9% gain from tracking over fixed azimuth.

I live in NW VT at 1600 feet on the western slope of Mount Mansfield and am
totally off grid here since 1989. I have two Two Seas racks (hand adjustable
in elevation) of 8 panels each wired series parallel for 24 VDC output each
to separate RV Products SB-50  MPPT controllers configured for 24 vdc in to
a 12vdc battery bank output. They run an older Trace 2012 2 KW(6KW peak
intermittent) modified sine wave inverter and a Prosine 1KW sine wave
inverter. I had set the elevation once a month on or about the 20th skipping
June 21st and Dec 21st of course.

-- 
Cheers ... 73 de brian, n1bq, underhill center, vermont



On 7/23/05 6:14 PM, "Tyler Allison" <tyler at allisonhouse.com> wrote:

> 
>> I actually want to build a parabolic trough and make it track the sun.
>> 
>> Everything we do here in the states is in inches, and I can get sheets
>> of stainless steel in 48x96 inches.  I've cut a template of wood in the
>> shape of a parabola that the curve is 96 inches long (thanks solver in
>> excel).
>> 
>> I'm actually not too keen on using an expensive GPS, my fall back is to
>> use a simple op-amp comparing the light falling on two photo transistors
>> inside a long tube.  As the sun moves, it will cast a shadow on one of
>> the photocells causing an imbalance.  The op amp will then drive a motor
>> forward a little.  I suppose it could be done better with a PIC.... that
>> would sense darkness at the end of the day and drive the array back to
>> home in the east.  My plan is to mount the trough at the angle of my
>> lattitude so that it is perpendicular to the sun, and adjust the
>> elevation near noon every day.... it would just take a little bump in
>> elevation everyday as the seasons change.
> 
> Check out this guy.
> 
> http://www.redrok.com/main.htm
> 
> I have a spare LED3X (I accidently purchased 2). I'll sell it to you below
> cost if you want it. Send me a private email.
> 
> You plug it into a 12V source and it has pin outs for a left and right
> dish actuator.
> 
> The one Im playing with works great..I just dont have strong enough
> actuators to move my solar panel tracker yet :)
> 
> Or you can use his schematics to build your own of course.
> 
> -Tyler
> 
> 
> 
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