homework [RE-wrenches]

Sun Apr 13 11:41:46 PDT 2008

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Max:

I am using Microstation.  There is no switch-- this is a drawing 
construction procedure.  My understanding is that you wanted to know the 
azimuth of the panels.  Your description of the project is not entirely 
clear so I may be completely off-base on what answer you are looking for.

Here is how I drew this:

1. I laid a solar panel flat on a plane (the roof).
2. I drew a line 90 deg from the panel. I call this the incidence line.  I 
rotated the panel (and line)15 deg from flat to the south.
3. I rotated the roof (and panel and incidence line) 22.6 deg to the west.
4. I rotated the entire contents of the drawing 26 degrees clockwise.
5. I drew a line south from where the incidence line intersects the panel.
6. I drew a line from where the incidence line intersects the panel flat 
and directly below the incidence line.  I call this the azimuth line.
7. I measured the angle from the azimuth line to the south line.  I added 
180 to this number.

WM

PS:  The next questions to ask are:  1. If there are multiple rows, how far 
apart should they be spaced to prevent inter-row shading?  And, 2. How much 
roof area will be lost to row spacing that could be used to add modules, if 
they were laid flat?

WM

At 10:28 AM 4/13/2008, you wrote:

>The reason for the tilt is simple, those paying for my design time have 
>asked that the panels be tilted..... The tilt will, in fact increase the 
>production value of the system (although I don't think the increased 
>production value is worth the extra cost of mounting hardware and labor, 
>but, I just work here. The important question for me is where in Autocad 
>3D did you find the info of the deg of tilt of the vector? I'm using 
>Autocad 2007, but I think a lot of the switches are in the same place as 
>the earlier versions....
>
>   Max
>
>William Miller <wrmiller at charter.net> wrote:
>
>Max:
>
>I guess you miss my point: Why tilt the panels up and incur aesthetic,
>structural and geometric headaches when there is so little to gain by doing
>so in a grid-tie system?
>
>Or, maybe I miss your point: Try this logic: If the roof slopes to 296 T
>and your rows are flat on the roof, the azimuth of your modules is 296. If
>the row is tilted up to vertical (even if it is running down the pitch)
>your orientation is 206. The azimuth sweeps between the two orientations
>depending on the tilt. My 3d cad shows the azimuth of the panels as 81 deg
>west of south (261). This is the orientation of the modules when viewed
>from overhead, ignoring tilt.
>
>Or, you are not explaining your question in a manner that I understand....
>
>William Miller
>
>At 10:46 PM 4/12/2008, you wrote:
>
>
> >The azmuth shifts because the panels are on a roof that is tilted 22.6
> >degrees to the west (296 degrees).
> > The panels are also tilted 15 degrees to the s/w (202 degrees) on the
> > roof that is tilted at 22.6 deg to the west (296 DEG)
> >
> > max
> >
> >William Miller wrote:
> >
> >Max:
> >
> >Isn't the azimuth you are looking for, uh, 206 degrees?
> >
> >Instead, consider this idea: I ran the CSI EPBB calculator for Beverly
> >Hills using 20 Solar World SW175m modules flat on the roof you described,
> >with an inverter to match. The calculator indicated the flat-against-the
> >roof system would provide 93% of the production of a south facing array. I
> >would avoid trying to tilt modules up and instead add approximately 7% more
> >modules and lay them flat.
> >
> >In my own humble opinion, tilting modules up in saw tooth fashion is
> >old-school.
> >
> >William Miller
> >
> >PS: You could run this model also in the PV Watts web based calculator. I
> >think you will find that the result is a bit more pessimistic, but still,
> >add even a few more modules and again, lay them flat on the roof.
> >
> >WM
> >
> >At 09:41 AM 4/11/2008, you wrote:
> >
> >
> >
> >
> > > I need help with my homework. I've got a project in Beverly Hills
> > > that is going to be sitting on a roof facing 296 deg at a 22.6 deg pitch.
> > > On this roof we will set rows of modules in landscape to the south at 15
> > > deg tilt and a bearing of 206 deg. I do all my drawings in cad, but I
> > > don't use the 3D component much. I thru it in cad and came up with the
> > > coordinates for the vector coming off the plane of the panel. However, I
> > > can't figure out how to find the angle that the vector is pointing in
> > > reference to the compass.
> > >
> > > Madd Max (been chewing on this for 2 days now)
> >
> >
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