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Installing a grid intertied
solar electric power system

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Overview System
Financing Panel
Hardware Grounding Rail
Part of the problem solving for my site has to do with the fact that none of the roofs are south facing.  As you can see, I had to build on to the south end of my workshop to mount the solar collectors that I use to heat the building.  So I originally envisioned mounting the panels to a 2 axis tracking array.  But that proved to be problematic, partly because its size would make it a giant eyesore in the garden.  I made a composite image (at left) and decided that this would not do.

By using a tracking array the modules always face directly toward the sun increasing the performance by over 30% per module.  But my friendly local solar dealer, Naoto Inoue at Solar Market,  advised me against that because the motors don't hold up well under heavy wind and snow load with a very large array.  Also the number of panels I would need could not fit on the largest tracking system available, so I would need 2 trackers at a cost of over $8000 each.  Even if I had room in the yard the money would be better spent on panels!

Just to get a sense of scale I built a model of my workshop in Google SketchUp and then a simple scale model of a tracking array.  Wow, that thing is huge!  And as shown it would only meet about 2/3rds of my needs!  This was my first attempt at using SketchUp and I could not figure out how to get the sun positioned correctly - so it is shining from the north in these images!  The pain of learning new software - at least it's free!

If you want to see an equally detailed installation blog of a ground mounted system, (left) then look at Gary Reysa's self-installed system that he put up in November 2009 in Montana.  Gary's web site, is THE site to see for all the DIY (do it yourself) projects you can imagine that relate to solar and sustainable energy.
SketchUp Shadow Settings toolbarSo my next thought was to install the panels on the roof, but since the ridge line is oriented to magnetic north-south I felt it would be best to try and tilt the panels up and mount them on both sides of the roof.  I got the sun position right and was able to move the virtual sun through the daylight hours and seasons to evaluate the shading issues and to optimally space the panels.  This is a really cool feature of SketchUp and I learned a lot about the shading issues arising from the stove pipe.  By moving the sliders around I could watch the shadows move across the model and see when there were shadows on the solar panels at different times of day and year (see movie below).
While this design could work, it would have a lot of trade-offs such as wind loading, not to mention it makes my workshop look like a giant Space Bug!  Not shown in this model is the tree-lined road on the east side of the building (near the car port) that would shade the east panels for much of the morning.  Notice that I refined the model with architectural details and modeled all of my solar collectors.  It took a few hours to learn the software, but it's worth it to see a nicely rendered preview.

So then based on advice from Naoto (my solar dealer) I decided to look at covering the entire west facing slope with panels.  This faces about 18 degrees south of due (solar) west, so it is acceptable.  Using the PV Watts calculator I learned that 30 panels would achieve the desired power rating and it seems that this is the best option for my site.  The panels have no shading from trees or other obstructions at all.  (We later decided to install only 21 panels to start with, based on fiscal realities).
The movie below was taken from the SketchUp screen, by saving "scenes" you can create transitions from one scene to the next.  Here I do a fly-around from noon to dawn on a June day, then show the sun arc from sunrise to sunset in June so you can see the shadows changing and the solar exposure hours of the panels.  If you pause the movie and grab the timeline slider (at top) you can move through time back and forth to watch the blue slider changing the time of day as the movie plays.

The roofing shingles are curling up at the corners, indicating that they are due for replacement.  The building is nearly 20 years old and the shingles were not high quality.  Since it would be more expensive to re-roof the building after installing panels I called some local roofers for estimates.  They confirmed that it would be wise to re-shingle the roof now rather than wait since it is nearing the end of its lifespan.  The lowest bidder ($2800) offered to install architectural shingles at no extra cost, and he will install them right over the existing shingles.  Architectural shingles are thicker and more durable and easier for the roofer to install.  I also chose a light gray because lighter colors last longer and reduce the heat buildup in the summer.  For more information look at the Cool Roof Rating Council site.

March 2013 update.   As I have been adding panels, I have been updating my Google SketchUp model  to pre-visualize shading issues before I install them.  The image at left was created before I installed the two panels tilted out on the South facing wall above my solar collectors.   I was able to learn that the  new panels would not adversely shade my solar collectors, particularly since I drain those during the summer months.

January 2014 update:  A study released in November 2013 shows that west facing solar arrays (in the northern hemisphere) are better at cutting peak electric demand on the grid because demand peak falls later in the day than solar peak in warm climates.  This validated my decision to use the available roof space.