Posted by Robert on May 21, 2008, 5:31 pm
On May 21, 7:46 am, d...@04.usenet.us.com wrote:
Interesting point, more hours of daylight in the summer, but the
azimuth is farther away in degrees from the panels in early morning
and late evening. What is the source of your figures? What do you
think the azimuth is today at your latitude at 7:28 A.M. PST, 8:28
A.M. PDT? Don't know if there's on online calculator for this. I
will have to figure out how to calculate this, or else measure shadows
at 8:30 A.M. tomorrow.
Posted by dold on May 21, 2008, 7:15 pm
http://www.gcstudio.com/suncalc.html provides a web page. I can copy that
to a spreadsheet where I have worked up a poor "vector offset" chart from
my PV panels, watching as the combined azimuth and elevation angles change.
7:28 am PST today? Why is that interesting?
7:28:00 civil, 07:21:15 solar, 28d10'01" elevation, 85d38'04" azimuth.
Sunrise at 04:52:41
Measuring shadows is cool, too. If I watch for the shadow to fall exactly
along one wall of my house, I can determine what the azimuth is for my
solar panels. Today, 12:58 PST is about my azimuth. The panel elevation
is directly to the sun at 10:43 and again at 13:28.
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5
Posted by Robert on May 22, 2008, 12:25 am
On May 21, 12:15 pm, d...@04.usenet.us.com wrote:
I was comparing sunrise on Jan 6 to the same clock time on May 21, but
that was not very interesting.
On May 21 the sun is always farther north than on Jan 6, except at
high noon when the azimuth is 180 degrees. Using the suncalc link
(great site) with the default settings for Pacific Grove, one hour
before high noon on 5/21 azimuth is 137 degrees. (Today a shadow
moves about 45 degrees in one hour in the middle of the day at these
latitudes, that is interesting, have to check that out.) On 1/6, one
hour before high noon the azimuth is 164 degrees, 27 degrees farther
south than at the comparable time on 5/21. So if your panels are
facing 180 degrees, this effect gives you less insolation (in the same
number of hours) in summer than in winter. But the increase in solar
altitude more than makes up for this in most cases.
Posted by stevey on June 9, 2008, 10:40 am
Dear Bob, ones who wanders about his array performance,
Your inverter numbers can be off by +/-5%.
For a quick instant performance check anyone (PV owner, or else)
can visit our FREE public service site--www.pvperformance.com.
By entering a few essential parameters about your solar array,
you'll get a number, or a range of numbers that indicates how
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specified date-time). Our number had demonstrated to be accurate
to +/-1% with Googleplex PV farm output. See--
Fourth posting, as validated by an engineer from EI Solutions.
For those in Silicon Valley, the Jasper-Ridge BIoPreserve on the
Stanford U campus has a well instrumented solar site, including good
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Please check our site out and give us brutal critique as you can.
We aim to refine it so that PV owners can get an instant assessment
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Posted by Bob on May 9, 2008, 12:59 am
On May 3, 2:48 pm, d...@02.usenet.us.com wrote:
There's no such thing as no interest, any more than there is a free
lunch. If you didn't take a loan, you could invest the money at least
at 4% Using $0,000 as the cost of the system (actually somewhat more
according to a later post) gives the following:
$0,000 @6%, payment $42/month = more than 20 year payoff
$0,000 @4% (to take your tax deduction into effect), payment $42/
month = almost 16 year payoff.
If you want to take rising rates into account, then it definitely
wouldn't be fair not to consider the compounded interest on your
$0,000 investment. I made a "what if" spreadsheet, rates rising 4%
per year, 4% interest on the $0,000, and payback would be about 13