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  • Panel on which side of the roof?

    Hello,

    I have a home with a low angle roof. The ridge runs almost exactly north-south with a slight tilt (see attached drawing)

    It is located on the US west coast at a latitude of 37.399.

    I have 10 panels I want to arrange in landscape orientation, in a row, tilted up towards south.

    On which side of the roof should I mount the panels?

    If the array runs along the roof the panels will not point to 100% to south. How much will this offset affect the output?

    Thanks!

    Illustration.JPG

  • #2
    put them on the left side as shown in picture. This will bring you closer to south.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

    Comment


    • #3
      Originally posted by Naptown View Post
      put them on the left side as shown in picture. This will bring you closer to south.
      hmm left? I was planning on putting them on the left however the picture shows them on the right side (eastern half of the roof). Did you mean "put them on like shown on the image (right side)" or "put them on the left side (opposite of what is shown on the image)"?

      Thanks

      Comment


      • #4
        The roof ridge will be giving you some shade, do you have AM or PM fog/clouds ?
        spreadsheet based voltage drop calculator:
        http://www.solar-guppy.com/download/...calculator.zip
        http://www.solarpaneltalk.com/showth...oss-calculator

        http://www.mike-burgess.org/PVinfo_2.html

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister ,
        battery lugs http://tinyurl.com/LMR-BigLug
        Setting up batteries http://tinyurl.com/LMR-NiFe

        gear :
        Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||

        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        Comment


        • #5
          Originally posted by Jaxx View Post
          hmm left? I was planning on putting them on the left however the picture shows them on the right side (eastern half of the roof). Did you mean "put them on like shown on the image (right side)" or "put them on the left side (opposite of what is shown on the image)"?

          Thanks
          on the left as the satellite image not the drawn image.
          Rich
          WWW.solarsaves.net

          NABCEP certified Technical Sales Professional

          http://www.solarpaneltalk.com/showth...Battery-Design

          http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

          www.gaisma.com

          Comment


          • #6
            Originally posted by Naptown View Post
            on the left as the satellite image not the drawn image.
            Thank you for the clarification!

            Originally posted by Mike90250 View Post
            The roof ridge will be giving you some shade, do you have AM or PM fog/clouds ?
            Yes, I life in the San Francisco Bay area and we have fog in the morning on many days. Evenings are usually clear.

            Comment


            • #7
              Originally posted by Jaxx View Post
              Yes, I life in the San Francisco Bay area and we have fog in the morning on many days. Evenings are usually clear.
              So that should cue you as to where to face your panels.... I also put mine on the west facing facet of my house, and produced power till sunset, which should work to your advantage with the ToU rates.

              FinalRoof.JPG
              Last edited by Mike90250; 01-04-2012, 12:07 PM.
              spreadsheet based voltage drop calculator:
              http://www.solar-guppy.com/download/...calculator.zip
              http://www.solarpaneltalk.com/showth...oss-calculator

              http://www.mike-burgess.org/PVinfo_2.html

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister ,
              battery lugs http://tinyurl.com/LMR-BigLug
              Setting up batteries http://tinyurl.com/LMR-NiFe

              gear :
              Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||

              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              Comment


              • #8
                Great, thanks a lot for your input!

                Also I need some help determining the tilt angle.
                Online calculators determine 37 degrees as the perfect all season tilt.
                The two elevation extremes are:
                In Dec: 29 degrees
                In July: 75 degrees

                How low could I possibly have the tilt set to without greatly affecting the output? I have a almost flat roof so wind impact and looks are a concern.

                Comment


                • #9
                  With a low slope roof say a 3/12 you could lay them flat on the roof with minimal losses. Play with PV Watts to determine exactly how much.

                  With elevated panels you may run into trouble with a homeowners assoc. (if any) or the AHJ requiring zoning variances or at minimum engineering for wind loading on the panels.
                  Rich
                  WWW.solarsaves.net

                  NABCEP certified Technical Sales Professional

                  http://www.solarpaneltalk.com/showth...Battery-Design

                  http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

                  www.gaisma.com

                  Comment


                  • #10
                    Originally posted by Naptown View Post
                    With a low slope roof say a 3/12 you could lay them flat on the roof with minimal losses. Play with PV Watts to determine exactly how much.
                    Even with the roof slope facing west instead of south?

                    Comment


                    • #11
                      Originally posted by Jaxx View Post
                      Even with the roof slope facing west instead of south?
                      Yes even with the roof facing west. A steep slope will reduce harvest a moderate one will reduce less.
                      Rich
                      WWW.solarsaves.net

                      NABCEP certified Technical Sales Professional

                      http://www.solarpaneltalk.com/showth...Battery-Design

                      http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

                      www.gaisma.com

                      Comment


                      • #12
                        Do not mess with tilting them up.

                        If you are anywhere from due E through S to due W, just go with the pitch and orientation the roof provides. The added cost of racking, labor and the engineering issues that are involved with the added wind load (you now have a sail catching considerable wind forces) are now way more than any potential benefit gained from slighly better production. Finally , your neighbors will hate the way it looks al tilted up and angular. You want solar to be a good thing , right? Moreover, making quality, high V connections between arrays is not the easiest. Simple is what works.

                        If you put 'em down co-planar with the roof pitch (same angle) you also won't have inter-row shading. Interrow shading in particular can be extremely damaging to output.

                        West is excellent:
                        you benefit from time-of-use rates in CA don't you? So west is even better than South, b/c you are credited high rates in afternnoon!
                        Morning fog also biases your decision to a sunnier West exposure.
                        If you are grid-tied a very flat angle is fine as year round production is what counts, not winter when the panels could be steeper.
                        As long as you don't go flat all the way, min. 5 degrees.

                        Good luck!

                        Comment


                        • #13
                          Can someone else also speak to the "tilt vs no tilt" topic specifically for my case?

                          Thanks a lot!

                          Comment


                          • #14
                            Hi Jaxx - Try using the Sharp solar calculator http://sharpusa.cleanpowerestimator.com/sharpusa.htm

                            It allows you to change the tilt angle and see the calculated affect on production - then you can determine whether or not it is worth the cost.

                            It does make a difference.

                            Russ
                            sigpic

                            Comment


                            • #15
                              use PV Watts to calculate http://www.nrel.gov/rredc/pvwatts/

                              My GT array in Los Angeles, was on a west facing roof, and produced just fine. AM fog was the deciding factor, if I had a south roof, there would have been little yearly difference in harvest !
                              spreadsheet based voltage drop calculator:
                              http://www.solar-guppy.com/download/...calculator.zip
                              http://www.solarpaneltalk.com/showth...oss-calculator

                              http://www.mike-burgess.org/PVinfo_2.html

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister ,
                              battery lugs http://tinyurl.com/LMR-BigLug
                              Setting up batteries http://tinyurl.com/LMR-NiFe

                              gear :
                              Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||

                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              Comment

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