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    My solar system

    I have alluded to this in various prior posts, but I thought I would post some pictures and mention some of the creative aspects of it.

    Ive had this idea brewing for years about building a structure and having the modules be the roof. It just seemed like such a waste to have two roofs! So this is what I came up with. The pitch is 36 degrees which is about ideal for here. I also wanted a large attic space to store lumber ( i have a sawmill and its kinda a hobby) so I certainly got that with the 36 degrees. Note the polycarbonate panels on the north side, a friend of mine came up with that idea. Its great, it lets tons of light in and doesnt cost anymore than siding.

    The most challenging part was figuring out how to mount the modules and keep the structure dry underneath. I thought long and hard on this. Originally I was going to "shingle" the modules, but I decided against that for several reasons, including shading. If the pitch wasnt as steep and/or there was more real estate on the edges of the modules that may have worked. I didnt want to rely on caulk or gaskets to try to keep water out, that just seemed like a hassle and prone to failure. In the end, I decided on the system of gutters and flashings you see in the pictures: a gutter is placed under the up-down seams, and a flashing goes under the east-west seams to channel water into the gutter. Only a couple times, when conditions are just right/wrong, I have at the flashing ice up and a little overflow happen. It seemed to be within a few inches of the gutter, so another piece of flashing would probably catch it. Ill keep an eye on it. The building is going to house my sawmill and tractor, so a few drips a few times a year is no big deal. I had also considered using a Z flashing - under the module, then up between and over the module below. That wouldn't have the overflow issue, but I was concerned about ice getting in between and freezing, maybe pushing the modules around.

    Its and interesting code quandary using modules as a roof. You would kinda have to call it a "structure" and not a "building" to be able to do it. Here things are so lax, nobody cares.

    How abou that transformer picture - ever seen a #10 coming out of a load break elbow? Thats 2KV Pv wire, transformer is 2400, tapped down all the way to 2280, close enough. I was too cheap to buy custom transformers. Runs about 500 feet to where it Tees into another 1900 foot line which goes from the service pedestal and transformer to the house.

    Its good to be an electrician sometimes.
    Attached Files
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

    #2
    Nice project.

    I don't know if you know of these, for your addition awning.
    https://lumossolar.com/

    Comment


      #3
      Originally posted by Sierrasparky View Post
      Nice project.

      I don't know if you know of these, for your addition awning.
      https://lumossolar.com/
      No I didnt know of those. Nice looking system. Makes for a real nice space. It appears they seal them with a tape product, 3M 4411. I guess good quality stuff will last a long time. Maybe Ill try that tape out on mine if those gutters trip more than occasionally.
      Ethan Brush - East West Electric. NY, WA. MA

      "You can't generalize"

      Comment


        #4
        One would think the roofing industry to be all over this, maybe take the PV guys out to lunch?

        ~RJ~

        Comment


          #5
          The interesting thing I see by reading is the panels work top and bottom. "bifacial solar cells allowing them to produce energy on both the sunny side and the back side of the module."

          I bet they are pricey!

          Comment


            #6
            Originally posted by Sierrasparky View Post
            The interesting thing I see by reading is the panels work top and bottom. "bifacial solar cells allowing them to produce energy on both the sunny side and the back side of the module."

            I bet they are pricey!
            The bigger problem is that for conventional mounting, either roof or ground, there is not a significant amount of light energy hitting the back side to be converted. If you were near the equator and had E-W facing vertical panels, you would get morning and afternoon production without moving the panel, but would give up production at solar noon.

            Comment


              #7
              Bifacial seems to guarantee that half of the cells you're buying won't see the sun.
              Master Electrician
              Electrical Contractor
              Richmond, VA

              Comment


                #8
                Originally posted by LarryFine View Post
                Bifacial seems to guarantee that half of the cells you're buying won't see the sun.
                I dont know much about them, but I assumed you were not buying two sets of cells, just hitting a single cell from both sides? I dont know if its as simple as using a translucent back sheet or there is more to it.
                Ethan Brush - East West Electric. NY, WA. MA

                "You can't generalize"

                Comment


                  #9
                  Originally posted by electrofelon View Post
                  ..How abou that transformer picture - ever seen a #10 coming out of a load break elbow? Thats 2KV Pv wire, transformer is 2400, tapped down all the way to 2280, close enough. I was too cheap to buy custom transformers. Runs about 500 feet to where it Tees into another 1900 foot line which goes from the service pedestal and transformer to the house.

                  Its good to be an electrician sometimes.
                  Amazing. Never seen 2kv solar.
                  That'll teach us to shut down before working hot.
                  What does that building disconnect look like?

                  Will that 2kv xfmr get fenced in, and hot lines put on power poles?
                  Wouldn't want your pup digging up, or chewing on that 2kv line.

                  Are micro inverters enclosed in wireway under roof?
                  Will those get hot under there?
                  How about module access for replacement?
                  If there is roof access, can modules support maintenance-persons weight repelling from rope & harness?
                  Roger Ramjet NoFixNoPay

                  Comment


                    #10
                    Originally posted by ramsy View Post
                    Amazing. Never seen 2kv solar.
                    That'll teach us to shut down before working hot.
                    What does that building disconnect look like?

                    Will that 2kv xfmr get fenced in, and hot lines put on power poles?
                    Wouldn't want your pup digging up, or chewing on that 2kv line.

                    Are micro inverters enclosed in wireway under roof?
                    Will those get hot under there?
                    How about module access for replacement?
                    If there is roof access, can modules support maintenance-persons weight repelling from rope & harness?
                    I didnt describe the electrical system very well. Its just two string inverters with 600 volt strings, standard split phase 120/240 on the AC side, connected to a loadcenter in the structure. The transformer is a step UP to 2400 (really -5% with the taps set down) due to transmission distance to my meter where it is stepped back down. So there is no 2400V gear other than the transformers and wire between them. They are standard pad mount transformers, I dont see any need to fence them in.

                    In case you are not real familiar with solar stuff, PV wire comes in 600V and 2kv ratings. Dc string voltages are either 600V or 1kv max, although 1500V equipment is just starting to come out. I am just using that 2kv PV wire as a convenient low cost way to run 2400 volts without getting into higher cost shielded cables and un-necessarily large sizes (#2 concentric neutral primary is just overkill for what Im doing). Its is run in 3/4 PVC, underground.

                    Although the siding and some details obviously are not finished, basically all that in the trusses is staying open and accessible and modules can be replaced from underneath in the trusses.
                    Ethan Brush - East West Electric. NY, WA. MA

                    "You can't generalize"

                    Comment


                      #11
                      Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?

                      Comment


                        #12
                        Originally posted by Sierrasparky View Post
                        Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?
                        Nope...Bad kitty I know. But from a practical perspective, the stuff is rated for direct bury so its "thicker than it needs to be" and has plenty of insulation if you compare it to similar cables such as L-824 5Kv airport lighting cable.

                        In hindsight, I probably would have just ordered custom 2KV transformers. they are only about $1700 each. The reason its so tempting to use 2400 is its so common and they can be found surplus for really cheap, typically $300-$400 plus some freight. The thing I discovered though is the efficiency and no load losses is quite a bit more on older units, so I ended up replacing a few of mine anyway when some newer ones came along. So all in all Im not that far below if I had just bought the nice new ones with the correct voltage from the beginning. Live and learn.
                        Ethan Brush - East West Electric. NY, WA. MA

                        "You can't generalize"

                        Comment


                          #13
                          Originally posted by Sierrasparky View Post
                          Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?
                          Good question: 2280 RMS = 3225 Max Peak-to-Peak
                          http://referencedesigner.com/rfcal/cal_04.php

                          @ 150% over-voltage Megger-test log of 2kv DC cable should show any deterioration over time.

                          If it fails underground the step potential above ground is what zaps walking animals.

                          5kv triplex on power poles is probably cheeper
                          Last edited by ramsy; 04-03-19, 11:53 PM.
                          Roger Ramjet NoFixNoPay

                          Comment


                            #14
                            Originally posted by ramsy View Post
                            Good question: 2280 RMS = 3225 Max Peak-to-Peak
                            http://referencedesigner.com/rfcal/cal_04.php

                            @ 150% over-voltage Megger-test log of 2kv DC cable should show any deterioration over time.

                            If it fails underground the step potential above ground is what zaps walking animals.
                            I dont think there is a different voltage rating for DC and AC conductors despite the peak AC being higher than RMS. Despite the fact that PV wire is usually used for DC, that doesnt mean it has a lower voltage rating (sorry if that is not what you were saying, sounding like that is what you were getting at). PV wire is covered under UL 4703 and UL 44. Note PV wire is also just type RHW-2 which is covered under UL 44: "Thermoset-Insulated Wires and cables".

                            5kv triplex on power poles is probably cheeper
                            There is nothing cheaper than using PV wire. Its say around .25 - .30 a foot for #10 (and as a MGN you can use 600V for the grounded conductor if you are really being cheap), and all you need is 3/4 conduit so you are looking at .80 a foot for everything. I guess it could be said that if you are not following the rules, then the world is your oyster as far as cutting costs
                            Ethan Brush - East West Electric. NY, WA. MA

                            "You can't generalize"

                            Comment


                              #15
                              Here's one Residential Line Extension Estimator that shows $40k to extend distribution poles 2400ft in nearby Idaho.

                              Another utility study estimates underground power is 4 to 14 times the cost of overhead lines of similar voltage and distance. That's when both projects are public works, with required engineering and standards compliance.

                              There would be no comparison in cost between those public-works projects, and a home-made DIY conduit run that ignores burial depth requirements, with PVC conduit subject to the elements, or cracking in winter cold, or water intrusion.

                              The NESC or other standard adopted at your State level, is what accident attorneys use in court to award property to injured clients. If trespassers can break that 3/4 PVC, and injure themselves, they 5-finger discount your estate. Permit violations are not necessary to prove.

                              From a liability perspective, running your 2kv wire thru an electric fence with high-voltage placards may be better than ignoring duty of care to trespassers, or State level burial depth standard for 2kv in PVC. We'll be there next week, my cross-eyed cousin will work the shovels.
                              Last edited by ramsy; 04-04-19, 06:51 PM.
                              Roger Ramjet NoFixNoPay

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