[amsat-bb] Re: Solar Power (I was wrong)

Doug Kuitula ka8qcu at pasty.net
Fri Oct 2 15:03:56 PDT 2009

Hi Bob,
While I'm at my summer place in the Upper Peninsula of Michigan (EN56), I
run my satellite station purely by solar power. It is not by any means a
high tech setup, but it works for me. I bought my  15watt solar panel from a
RV (recreational vehicle) center, and charge up two 26 amp hour gel cell
batteries. I also use one of those " $10 Dayton specials" power units with a
17ah battery and 400 watt inverter. This runs the laptop and rotator. But
not for long. I think I've got less than $250 into the whole system. This is
not by any means the most effective or efficient system to have, but it is
portable and works for Field Day.
 So if I make contact with you from EN56, it's done from solar power.
 73 de Doug KA8QCU

----- Original Message -----
From: "Robert Bruninga" <bruninga at usna.edu>
To: "'Greg D.'" <ko6th_greg at hotmail.com>; <ptrowe at yahoo.com>;
<amsat-bb at amsat.org>; <wb3jfs at cox.net>
Sent: Friday, October 02, 2009 14:27
Subject: [amsat-bb] Re: Solar Power (I was wrong)

> > ... I have... a roof angle exposure that is
> > not solar-friendly...
> That was another error I had made in my situation.
> Again, there is a BIG difference between solar design for
> stand-alone battery systems (must point south, optimum angle,
> etc) and grid-tie systems that can be anything from SE to SW and
> even FLAT and still be only a few percent off peak!.
> The economics are entirely different.
> The remote/battery system, MUST provide a minimum power on the
> worst winter days and weather of the year.  It MUST be optimized
> for winter.
> On the other hand, the grid tie system only has to have a good
> AVERAGE power averaged over a year.  And you can make more money
> in a month of summer sun making money at HIGH payback rates than
> you can get all winter (3 months).
> Even a FLAT array makes more power in the 3 summer months than
> the optimum tilt angle array does.
> And lastly, anything pointed SE to S to SW is about the same for
> a grid-tie system.  You lose at most about 5% SE or SW compared
> to South.  Again, the reason is not obvious.  But any tilted
> array is only going to see the sun for 180 degrees of path
> across the sky.  Even the ideal South facing tilted array does
> not see the morning sun nor the evening sun in the summer when
> you are getting your most payback..  It only sees the midle 6
> hours.  Since the  sun is up much longer than that most seasons,
> then getting those 6 hours averaged before noon (SE) or getting
> them in the afternoonn (SW) makes little difference for a
> grid-tie array, though, I'd favor SW, since peak electric rates
> apply longer in the afternoon than in the morning.  So you want
> to maximize your power when electricity rates are highest.
> Again, I am sharing this off topic with everyone, because I too
> learned that my thinking was all wrong based on my previous
> experiences with stand-alone power systems and that a
> grid-tie-system has completely diffeerent economics to my normal
> thinking...
> You can play with all the angles and directions for grid-tie
> systems on-line with the solar energy calculator here:
> Yes, SOUTH with a latitude tilt is best... But based on annual
>  Southeast only lost 5%
>  Southwest only lost 5%
>  Droping the tilt to the angle of my roof 25 deg only lost 1%!
>  Droping the tilt to FLAT on the ground only lost 14%
>  (but if I tilt them up to 45deg Sept to April) I GAIN 20%!  And
> that is a +5% over optimum south.
> http://www.nrel.gov/rredc/pvwatts/version1.html
> On the other hand, ANY shade will significantlly cut into your
> power budget.
> Bob, Wb4APR
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