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  • New install- tilt vs direction

    I'm building a new barn at around 37 degrees lat with plans to put solar panels on the roof. It would be difficult to orient due south due tot he lay of the land. The purpose for the barn prevents angling/tilting the panels ideally for winter use when my electrical bills are highest. My question is this- which is more important from an efficiency standpoint- tilt or azimuth?

  • #2
    Originally posted by CaliBerger View Post
    The purpose for the barn prevents angling/tilting the panels ideally for winter use when my electrical bills are highest. My question is this- which is more important from an efficiency standpoint- tilt or azimuth?
    If I were you, I'd plug in various options (tilt and azimuth) into pvwatts to get estimates for my locale.
    I'd change only those 2 variables while keeping the others constant.


    Are you in CA (guessing yes, because of your name)? Is this going to be grid tie? If answer is yes to both then you probably have net metering available to you. And then what matters is your total kwh per year, not matching your kwh used each month.

    If you can't do a southern orientation, orienting with the ridge running N/S and having some on the east roof and some on the west roof can be a pretty good solution too.
    It's probably best in that situation to have a nearly straight N/S ridge, rather than NW/SE and having some panels pointing somewhat north. (again - PVwatts would be good to explore options)
    An east-west combination is where you can push the DC-watt to AC-watt ratio up more on your inverter and still not have clipping.

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    • #3
      It depends. One way to look at it is that you want to maximize the yearly integrated daily energy production. Right !

      Reality is, it's hard to generalize, but both are important, one sometimes more than the other for some times of day, or some seasons, then the other. It's a very non linear process. Then, there's shading considerations which vary over the course of a year, minute by minute. Shading considerations aside, it's often better to have higher tilts for farther off south azimuths, but that rule of thumb works better for far off south azimuths. The easy way to get the best year round orientation to maximize production (but that may not necessarily get you the most most bill reduction if you'll be on some type of net metering arrangement) is to get familiar w/PVWatts. After getting familiar, start w/the most southerly azimuth possible. Then, vary the tilt by ~ 5 deg +/- for that azimuth. Then, do that for several tilts. Repeat the process for a different azimuths and tilts. Make a table of the model's annual output. Once familiar w/ PVWatts, the process will take ~ 1 hr. for maybe 15-20 runs. Use 5 deg. increments for both azimuth and tilt. Without shading considerations - which ought to be avoided as much as possible anyway, and which you may well be able to eyeball, you'll probably narrow in on something like an az. of maybe ~ 200-220 deg. and a tilt close to your latitude for annual max. production. Don't be too surprised if the variation in output +/- 20 deg. off optimum on az., and maybe 10 deg. off optimum on tilt don't produce a big penalty on output. My guess is you'll probably narrow in on a tilt close to 37 deg., +/- 5 deg. or so for an unshaded orientation that produces the max. annual output. Maybe. This is not an exact science.

      Why not a ground mount ? There is no eleventh commandment that says panels must be on a roof.

      Do you have net metering available ?

      What is you annual usage ?

      How much of your annual usage offset is the economically optimum ?

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      • #4
        Thank you both
        The PVWatt calculator is exactly what I was looking for

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        • #5
          Originally posted by CaliBerger View Post
          Thank you both
          The PVWatt calculator is exactly what I was looking for
          For my part, you're most welcome.

          Good luck.

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