DIY Shade Finder Tool Takes The Tedium Out Of Solar Surveys


[Steven Dufresne] does a lot of tinkering with solar-powered applications, a hobby which can be very time consuming if done right. One process he carries out whenever building a solar installation is creating a sun chart to determine how much (or little) sun the target area will get.

The process requires [Steven] to take elevation and Azimuth measurements of many different points, which often consumes about half an hour of his time. While taking measurements recently, he started thinking about how he could improve the process, and came up with a stellar solution that reduces the process down to a one-minute task.

In short, his shade finder tool uses a pulley, a pair of rollerblade wheels, and a pencil to accomplish a full shade survey in under a minute. The science behind the tool is best explained by [Steven], so be sure to check out his site for plenty of details and diagrams.

We have to say that we’re extremely impressed by his shade finder – hopefully his work can help others maximize the efficiency of their solar solutions.

Stick around after the jump to see a short video of the shade finder in action.

20 thoughts on “DIY Shade Finder Tool Takes The Tedium Out Of Solar Surveys

  1. Nice hardware application for this particular geometry problem. I believe that a smartphone App could accomplish the same results even more quickly and accurately and would be more appropriate for the average homeowner whose need of specific site information would be a one time thing.

    Still, a nice piece of kit, especially if you are heavy into solar installation.

    1. My thought as well. He could have simply made a board with a chicken wire fence wrapped around in a circle for the grid, and shot a panorama image with a camera through the grid.

      Some geometric processing later on the computer and you get a nice shade chart.

    2. Needs a wide-angle lens so close to a building, like in the photo.

      In general, a 360° panorama is a rather elegant solution (and self-calibrating as well), especially if the picture includes the sun. Favourable contrast (the lower the sun, the better, with clear skies) could even allow for automatic recognition of the skyline.

      But why, for example, Hugin can’t make a seamless panorama from FinePix F10 photos? I tried a few times, a few months apart, each time reading various tutorials and tips anew, and the seams still were unacceptably visible. (Only a truly seamless panorama by definition automatically provides the scale in degrees per pixel.) Perhaps it can correct distortion by known professional lenses only? Focus-free cameras, then, would be even worse.

      1. Generally the distortion depends on the zoom level.
        There is probably an average level, where the distortion is minimal.
        Try it out with different zoom settings on a brick wall, you will se it.

        Then when using the optimal zoom hugin should work better.

      2. Hugin is really finicky the last time I tried it. It’s almost useless unless you do everything exactly right, and it gets confused easily if you have repeating patterns in the picture.

      3. I don’t know about the Fine-Pix autopanoramic shots, but the Coolpix I have used did most of it’s panorama composition internally. Using it’s guide markers, and stitching the resulting images resulted in a messy panorama, I suspect because the camera uses some internal gyro or accelormeter data when it does it’s own stitching, even a simple compass could help if it’s internals were smart enough. Another reason could be a change in the camera’s focal length as you pan, or an arbitrarily large focal area. I found that Hugin completely failed at assembling screenshots from a video game, because the infinitely small aperture would not let it discern fore, middle, and background.

  2. There is a much easier way to do this job. It was invented by a woman in California at least 30 years ago.

    At the center of a plywood 5″ radius half circle, you put one of those super wide angle door security viewers. You put a round bubble level and a compass to orient the board. A thin sheet of clear plastic wraps around the half circumference, standing up vertically for 6-12″. On that plastic is printed the path of the sun as viewed through the door viewer. There were lines showing the solar path for each month. There were “vertical” lines for noon and the full day in hours. These grids were sold calibrated for every 2 degrees of latitude; you ordered for your area.

    You could hand hold the device as you could see the compass and bubble level thru the viewer, or tripod mount. The sun was safely dimmed by the fish eye viewer. It always appeared at the correct time and date on the grids.

    Solar exposure for your position was viewed as a single image. You could pick any month line, and following it, see at what time the sun “rose” and “set” in that month and what was causing the shading. There were no moving parts, and all the data you wanted in a single view.

    Of course, the patent is long expired. It would be neat if some enterprising person were to calculate the grids and print them! I built mine after she had quit business, but still had grids to sell. It didn’t take much over an hour and cost maybe $5 to make, plus about $15 for grids. My “knockoff” could be documented and posted, once I figure out who I last loaned it to!

  3. I’m glad you guys like this. It was loads of fun to design and build, and as loudnessduck said, worth it even for one solar panel. I wouldn’t patent it since there’d be no market. There’s already one out there, that sounds like what Bob Spafford is talking about above, called the Solar Pathfinder that’s so childishly simple to use that it’d be hard to beat, except maybe with a very smart phone app that uses data from an accelerometer and compass to stitch photos together.

  4. I think I’d just take 3 photographs, Sout-East, South, and South-west from a horizontal platform and make an overlay in Gimp or similar, but then I would’nt have so mutch fun building my stuff.

    I am curious about his Winter Solstice Sourdough Sunshine Cake though…

  5. Solmetric makes an iPhone app that does this very quickly and easily. There are also a couple of low cost Android apps that do this. Overall, the Solar Pathfinder or SunEye are the best investment for folks doing this professionally. For a curious homeowner, either use the app or build this device, if you have the time.

  6. Solmetric iPV (for iPhone) and Solar Shading by Comoving Magnetics (for Android) also do this. I have not tried Solmetric’s version, but Solar Shading is pretty accurate when compared to a Solar Pathfinder. I’ve tested it against the Pathfinder with a few different skylines…

  7. I used ‘shadows’ a shareware sundial creation program to treat the equator facing aspect of the new house as a vertical sundial, and the overhanging eave formed the gnomon, and the resulting sundial with dimensions scaled to 1mm = 100mm allowed window sizes to be established such that winter solstice sun came in at the top of the window, and summer solstice sun stopped at the bottom of the window, optimising solar gain for passive solar heating and cooling of the house.

    The same approach can be used to establish window shade sizes for addition to the various sides of an already built house.

    Again, this sort if thing was being done in the 1970s, and we are relearning it all again.

  8. Steven D. Although there’s as stated probably a dozen different ways to accomplish the same I enjoyed watching your videos.

    Even though some of the vids showed very basic skills I love the idea of passing on these trades and handcraft for the younger generation. Things that you learned naturally as a kid seem to have vanished with all the computers and games.

    Nice to see someone care about the detail of things.

    1. Mr-Midnight. Too often it’s the basics that are missing. So I often try and start there. And since I made this video available I’ve learned a few ways I wasn’t aware of for doing solar shading. Ka-ching! (sound of me profiting from the above comments.)

  9. Smart phones use GPS for that nav app. Look up GPS errors in Wikipedia. They are small if you are trying to find a street address, but can be something again if you are trying to find if that oak tree will shade a solar panel this Summer.

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