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

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  • #16

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

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

    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, 4.2 kw APC UPS powered either by battery or a Prius. Really.

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    • #17

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

      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

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      • #18

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

        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...
        10-Astronergy 235 watt panels
        Fixed 180* south face-No tracker
        Midnite Solar Classic MPPT Charge Controller 250V
        Mini-Magnum MS4448PAE Power Center
        16(ea) S-530 Surrette Batteries 800aH @ 48VDC 38,400 watt hrs.
        Lat/Long 37.8 N 113.1 W

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        • #19

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

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

          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.

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          • #20

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

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

            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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            • #21

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

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

              Originally posted by ggunn View Post
              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.
              to add to what ggunn said here, i would say when you find the angle on the equinox for solar noon that aiming for solar noon is not going to give you optimum power harvested because that is only the peak angle and not the average angle around that time. at all other times that day the sun is lower in the sky as well as a bit farther east or west. aiming below the equinox peak sun position will still reap good power at noon with little degradation and bring the focal point closer to the sun positions at other times just off of solar noon. this is why the extra 15 degrees in tilt is often added. this makes it optimum for that time of the year, barring other factors, and does not make it optimal for the winter btw. this is the best average production reaped on the day of the equinox which is the average of all seasons. a winter peak will be latitude + 23.5 degrees as long as that answer is 90 degrees or less and being it is a peak the sun will sit lower in the sky than that angle for all other times.
              Last edited by niel; March 29th, 2012, 10:21.
              NIEL

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              • #22

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

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

                Thats a good point Niel, thats the way a pivital tone arm on a record player is set. Instead of intersecting the groove at 90 degrees at the center of the arc it is set to intersect it twice at 90 degrees, once at the rise and once at the fall of the arc. This allows for overall less tracking error particularly at the extremes of the arc.
                However I suspect that even though setting an array at solar noon on the equinox would not provide the best output for that time of year, it would be a good compromise annually.
                The suns angle at solar noon on the equinox I believe is the same angle as your latitude.
                Last edited by 65DegN; March 29th, 2012, 17:17.
                6 SolarWorld 175 (1 KW), 14 Arco Solar 16-2000 (~1.5KW total), 15 REC 250 (3.75 KW) 2 KW 48V Whirlwind turbine, Outback 3648, 8 Dekka Solar L-16's, Outback FM80, Midnite Classic 150, Honda 2000i backup, & Generac 5KW.

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                • #23

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

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

                  Originally posted by niel View Post
                  to add to what ggunn said here, i would say when you find the angle on the equinox for solar noon that aiming for solar noon is not going to give you optimum power harvested because that is only the peak angle and not the average angle around that time. at all other times that day the sun is lower in the sky as well as a bit farther east or west. aiming below the equinox peak sun position will still reap good power at noon with little degradation and bring the focal point closer to the sun positions at other times just off of solar noon. this is why the extra 15 degrees in tilt is often added. this makes it optimum for that time of the year, barring other factors, and does not make it optimal for the winter btw. this is the best average production reaped on the day of the equinox which is the average of all seasons. a winter peak will be latitude + 23.5 degrees as long as that answer is 90 degrees or less and being it is a peak the sun will sit lower in the sky than that angle for all other times.
                  Consider the numbers for Austin, TX (from http://rredc.nrel.gov/solar/old_data...2/state.html):

                  "SOLAR RADIATION FOR FLAT-PLATE COLLECTORS FACING SOUTH AT A FIXED-TILT (kWh/m2/day), Percentage Uncertainty = 9"
                  "Tilt(deg)"," ","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct ","Nov","Dec","Year"

                  "Lat - 15 ","Average", 3.7, 4.4, 5.2, 5.6, 5.8, 6.4, 6.7, 6.5, 5.7, 5.0, 4.1, 3.5, 5.2
                  " ","Minimum", 2.9, 3.5, 4.2, 4.8, 4.5, 5.6, 5.5, 5.6, 4.8, 3.9, 2.8, 2.9, 5.1
                  " ","Maximum", 4.5, 5.3, 6.1, 6.9, 6.6, 7.1, 7.3, 7.2, 6.6, 5.7, 5.0, 4.6, 5.5

                  "Lat ","Average", 4.2, 4.8, 5.4, 5.5, 5.5, 5.9, 6.2, 6.3, 5.8, 5.4, 4.6, 4.0, 5.3
                  " ","Minimum", 3.2, 3.7, 4.3, 4.7, 4.3, 5.2, 5.2, 5.4, 4.8, 4.1, 3.0, 3.2, 5.1
                  " ","Maximum", 5.2, 5.9, 6.4, 6.8, 6.2, 6.5, 6.8, 6.9, 6.8, 6.2, 5.8, 5.4, 5.6

                  "Lat + 15 ","Average", 4.4, 5.0, 5.3, 5.1, 4.9, 5.1, 5.4, 5.7, 5.5, 5.5, 4.8, 4.3, 5.1
                  " ","Minimum", 3.3, 3.7, 4.1, 4.3, 3.8, 4.5, 4.6, 4.9, 4.6, 4.1, 3.1, 3.4, 4.9
                  " ","Maximum", 5.7, 6.2, 6.3, 6.4, 5.5, 5.6, 5.9, 6.3, 6.6, 6.3, 6.2, 6.0, 5.4


                  The yearly averages for latitude, latitude + 15, and Latitude - 15 are bolded. Latitude tilt is the highest production, but it's only a smidge greater than -15, which is a little greater than +15. Also note that the uncertainty is 9%, which is much larger than the differences. It's a wash for here, anyway.

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                  • #24

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

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

                    To state the obvious, the further you are from the Equator the more drastic the difference between Winter & Summer insolation and thus the more important it is to have the right panel angle.
                    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

                    Ohm's Law: Amps = Volts / Ohms
                    Power Formula: Watts = Volts * Amps

                    Comment


                    • #25

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

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

                      ggunn,
                      i keep forgetting summer intensities are much stronger than winter barring other influences such as snow or water reflections. figures from sites like that are quite interesting and even looking at my area it is strange to note that even for january that it varies little from 0 up to 90 degrees.

                      here's the kwh/m^2 for january
                      0------ 1.7
                      lat -15- 2.4
                      lat----- 2.6
                      lat +15- 2.7
                      90----- 2.5

                      to optimize winter what i said is good, but there's no getting around the higher figures of summer production. off grid should go to 2 angles minimum as there wouldn't be just 1 viable angle. it would benefit gt as well going 2 angles, but one angle can work for them as they bank power during the summer.
                      NIEL

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                      • #26

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

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

                        Originally posted by niel View Post
                        ggunn,
                        but there's no getting around the higher figures of summer production. off grid should go to 2 angles minimum as there wouldn't be just 1 viable angle. it would benefit gt as well going 2 angles, but one angle can work for them as they bank power during the summer.
                        2 angles is just what I did after looking at the graphs on the page I linked. I am at 23S and I am using around 20 during spring/summer/fall and close to 42 during the winter. The angles are not exactly as recommended but it was a practical thing when building my frame.
                        Last edited by Les Nagy; March 29th, 2012, 21:50.

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                        • #27

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

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

                          Originally posted by Cariboocoot View Post
                          To state the obvious, the further you are from the Equator the more drastic the difference between Winter & Summer insolation and thus the more important it is to have the right panel angle.
                          Of course. Up at the north pole where you live there IS no insolation in winter. ;^)

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                          • #28

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

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

                            Originally posted by ggunn View Post
                            Of course. Up at the north pole where you live there IS no insolation in winter. ;^)
                            Yes, but in Summer it's 24 hour sunshine!
                            1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

                            Ohm's Law: Amps = Volts / Ohms
                            Power Formula: Watts = Volts * Amps

                            Comment


                            • #29

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

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

                              Originally posted by Cariboocoot View Post
                              Yes, but in Summer it's 24 hour sunshine!
                              Yeah, but you have to use a single axis tracker with a vertical axis to capture it.

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                              • #30

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

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

                                Originally posted by ggunn View Post
                                Yeah, but you have to use a single axis tracker with a vertical axis to capture it.
                                Nah, we put the panels on a turntable and spin 'em 'round!
                                Storage is the big problem: the self-discharge rate even on AGM's over six months ...
                                1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

                                Ohm's Law: Amps = Volts / Ohms
                                Power Formula: Watts = Volts * Amps

                                Comment

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