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Thread: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

  1. #11
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by techntrek View Post
    A question I didn't see asked yet - is this for a grid-tied system or an off-grid system? For grid-tied I would use the angle that gets you the best output year-round. For off-grid use the best angle for winter production.
    I guess many offgridders will use more power in the winter, but I wouldn't think that's universally true.

  2. #12
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by rss2q View Post
    Simply put, I just want to find the best tilt that you should mount a fixed solar panel system to receive the best results year round.
    The optimal angle (as techntrek pointed out) may depend on whether you are on or off grid.

    Another consideration is that the optimal direction for you may not be due south. This may be because of local conditions such as fog in the morning or shading in the afternoon, for example. If you are doing a roof mount, and your roof is not facing due south, the calculations for optimal tilt are different.

    Still another consideration (affecting both tilt and direction) may be the timing of your loads. This is true if you are off grid and may be true on grid depending on what net metering arrangements or time-of-use you have. With panels as cheap as they are now it may be cost effective to have split your panels into two arrays (with two charge controllers) with different tilts and directions. If you are using microinverters you might even have more than two tilts and directions.

    rss2q, tell us more about your location, climate, loads, and type of system.

    Quote Originally Posted by ggunn View Post
    I guess many offgridders will use more power in the winter, but I wouldn't think that's universally true.
    I use less in the winter because a large portion of my energy budget is a freezer in a detached (very cool in winter) outbuilding. If I ever get air conditioning or dehumidifier my summer energy use will be still greater.
    --vtMaps
    4 x 235w Samsung, Outback fm60 & vfx3524 & mate, Midnite E-panel, four Interstate L16, Trimetric monitor, Honda eu2000

  3. #13
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by vtmaps View Post
    I use less in the winter because a large portion of my energy budget is a freezer in a detached (very cool in winter) outbuilding.
    That's also my experience. The colder the weather the less that freezer runs, thus the less energy used. Come summer my consumption goes way up because the freezer really has to work.
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

  4. #14
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by ggunn View Post
    I guess many offgridders will use more power in the winter, but I wouldn't think that's universally true.
    But the optimum winter angle will often produce just as much if not MORE power in the summer anyway, even at the less-optimal angle. For on-gridders this doesn't matter, since they can use higher summer production to offset lower winter production, but off-gridders are basically sizing their systems based on the months of lowest productivity, and so it makes sense to optimize to this condition.

    Example: PV watts says that 35 degrees is the optimal angle for year-round production at my location. For a 5 kW system, standard derate, that means a total of 6158 kWh, with 328 in December and 600 in June.

    If I tilt that same array up to 60 degrees, I produce only 5679 kWh per year, but now I produce 365 in December and 459 in June. Tilting the array even more loses production in both summer and winter, unless the snow-glare effect is prevalent.

    It's not a huge difference, but that way I can squeeze a few more kWh into the winter months, when the sun is scarce, and I still generate excess power in the summer months, so who cares about kWh I can't use anyway?

  5. #15

    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Here is a great resource. (sorry, US only)

    This page calculates the altitude and azimuth of the Sun (or Moon) at multiple times during any day between 1700 and 2100. Simply specify the object, date, tabular interval, and place:

    http://aa.usno.navy.mil/data/docs/AltAz.php

    Our tax dolars at work.
    Last edited by SolaRevolution; March 27th, 2012 at 20:50 PDT.

  6. #16

    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by jagec View Post
    It's not a huge difference, but that way I can squeeze a few more kWh into the winter months, when the sun is scarce, and I still generate excess power in the summer months, so who cares about kWh I can't use anyway?
    This is what I was alluding to in my last post, thanks.
    12 kw Generac, Honda EU3000is, Yamaha EF2400is FOR SALE, 4.2 kw APC UPS powered either by battery or a Prius. Really.

  7. #17
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    I found this link here on the forum I think. I think it is quite useful.
    http://www.macslab.com/optsolar.html

  8. #18

    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    If you didn't know shirt from shin-ola you can set the angle by
    1.) know "solar noon" at your local
    2.) use a 12" stake with a true, square 90* base
    and place it on the panels, adjust said panels until there is no shadow.

    Way too simple...
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  9. #19
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by plongson View Post
    If you didn't know shirt from shin-ola you can set the angle by
    1.) know "solar noon" at your local
    2.) use a 12" stake with a true, square 90* base
    and place it on the panels, adjust said panels until there is no shadow.

    Way too simple...
    But on what day? Summer solstice? Winter solstice? Equinox? On the equinox would tell you the optimum tilt for yearly average production if no other factors are in play. Of course, other factors are always in play.

  10. #20
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    Default Re: KISS: Find Optimum Winter Tilt Angle or Best Year Round Tilt for Fixed Solar Panel

    Quote Originally Posted by vtmaps View Post

    Another consideration is that the optimal direction for you may not be due south. This may be because of local conditions such as fog in the morning or shading in the afternoon, for example. If you are doing a roof mount, and your roof is not facing due south, the calculations for optimal tilt are different.
    Of course, most residential roof mounts are on slanted roofs and are for all practical purposes restricted to the azimuth and tilt of the roof. If you installed racking that would mount the modules at a different tilt than the roof, the extra expense incurred would likely far exceed the benefit gained.

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