To elaborate on the earlier comments, latitude +15 is usually employed to
provide maximum WINTER performance on a stand alone application, when days
are short, atmospheric interference is at it's greatest, and cloudy days are
more likely. This array angle positions the surface of the solar panel at a
right angle with the sun (angle of incidence), so the panel works best in
the middle of winter. During the summer, when the sun is more intense, days
are longer and less cloudy, you do lose some power, but it is of no
consequence, as the system will generally be fully changed by noon.. A
stand alone PV system designed to work year round is always designed with
winter conditions in mind, not summer or average annual insolation.
I don't know of any maps that define insolation or wind speed by zip code,
that would be too site specific, and almost impossible to account for micro
climate conditions. Most people make the fundamental mistake of trying to
size a PV system too closely, thinking they are making the best economic
choice. Wrong. You must take into account system losses, battery aging,
less than perfect site conditions, and gradual degradation of system
performance, on the order of .5% to 1% per year.
The most economic choice for a system will most likely be the most
troublesome and costly over it's lifetime. We do offer a sizing matrix on
our website for PV sizing that is based on old National Weather Service data
collected by the University of Wisconsin. Although newer data shows greater
insolation levels than we present, we have taken a conservative design
approach, as we place greater emphasis on reliability and dependability than
cost. This map and matrix have worked well for 15 years, as our systems
have never failed due to sizing errors. You may view this map and our
method at www.solarcraft.net/uni-pak/selection.html
My point is, you should NEVER size a PV system without a safety margin, and
searching for very local weather information may lead you down the wrong
system design path.
----- Original Message -----
From: "C.C. Foster" <c_c_foster@...>
Sent: Thursday, November 07, 2002 8:25 AM
Subject: Re: [hreg] FW: Installation
> Here is a brief discussio regarding angle of solar panel orientation.
> Please reply to c_c_foster@... if you prefer to get more data
> without clutter on the common site.
> The orientation (15 + latitude) has been generally accepted to be a good
> comprimise to achieve high solar energy harvest. One corrloary that is
> important is the highest solar intensity is when the sun is directly in
> with the solar receptor.
> Consider this example: your body can sense the solar energy is less early
> the morning or late in the afternoon and greatest about noon. A body can
> sense, also, that the solar energy is greater when the sun is high above
> southern horizon (summer).
> Although the solar receptor (photovoltaic) uses a different form of solar
> input, the energy produced by a solar harvestor in highest about noon when
> it receives direct rays from the sun.
> An active system that includes sun tracking to keep the solar receptor
> at the sun is slightly more effective and much more expensive to build and
> maintain on earth. In some applications like the space vehicles, the value
> of aiming more than offsets the complexity and cost.
> >From: Robert Bruce Warburton <warbur2@...>
> >Reply-To: email@example.com
> >To: firstname.lastname@example.org
> >Subject: Re: [hreg] FW: Installation
> >Date: Mon, 04 Nov 2002 14:46:23 -0600
> >Do the maps do a detemination of where a site by zip code or county
> >would be viable for wind or solar power? I realize that in terms of
> >average daily total radiation falling on a horiontal surface, that far
> >west Texas south of New Mexico and or near the New Mexico border has
> >over 20,000 kilojoules per square meter. Are there other considerations?
> >Also, why is an angle of roof incline ideal if it is 15 degrees above
> >the latitude and facing due south?Mike Ewert wrote:
> > > Virtus is the company that did the fine renewable energy resource maps
> > > featured on www.infinitepower.org If you can help them locate solar
> > > projects in east Texas, please e-mail Steve directly at the address
> > > below.
> > > -----Original Message-----
> > > From: Steve Lain [mailto:lain@...]
> > > Sent: Friday, November 01, 2002 4:17 PM
> > > To: hreg@...
> > > Subject: Installation
> > >
> > > Hi,My name is Steve Lain and I work with Virtus Energy Research
> > > Associates in Austin (Mike Sloan). We are doing research on small
> > > scale renewable projects in TX. Can you contact me about any
> > > installations you know about in the E Tx area? Thanks, Steve
> > >
> > >
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