[aprssig] Shack backup power

Bob Bruninga bruninga at usna.edu
Thu Jun 9 09:41:26 EDT 2011

>> in the summer when the sun rises in the NE and sets in the NW.

> I hope you mean SE and SW respectively. 
> No one North of latitude 23.5deg N (Tropic of Cancer) 
> will ever see a northerly component of the sun's azimuth. 
> See HO-249, or the overhead figure-8 on most globes.

Nope, I meant NE and NW in the Northern Hemisphere above the tropic off
cancer. Actually it is closer to rising to the ENE and sets to the WNW in
the summer here in Maryland.  Remember, in ALASKA above the arctic circle it
even goes from NORTH around all 360 degrees and back to North in the summer.

That is why I share this solar information, since it has been so revealing
to me and counter-intuitve.  I wanted to share this with other hams who only
think solar panels must be south (that ONLY applies to off-grid battery

Grid-tie is completely different because it does not need to guarantee some
minimum winter power.  The only thing that counts with grid-tie is annual
total power, and directions other than due south still produce significant
power.  Even a 20 degree pitch NORTH facing roof in my area (Maryland) will
produce 60% of the total annual energy as the ideal south-facing array.

That is why you no longer see solar panels mounted on odd-angle-stilts on
roofs anymore to point south.  Becuase just about any orientation will
produce plenty of solar power during the time of year that is best for that
roof, and that makes up for other months of the year when it is less than
optimum.  Now you see arrays just mounted flat on whatever direction the
roof points.

You can do an instant analysis of any angle and any direction using the
"PVWATTS" calculator that you can find by googleing.

Bob, Wb4APR

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