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Solar Tracker versus Snow - The snow won

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  • Solar Tracker versus Snow - The snow won

    The town adjacent to me is a summer colony and sometimes the residents like to compete to show how progressive's they are. There are a lot of old summer homes and converted camps. The latest subtle way of letting the neighbors know that the owner is "greener" is a solar array. The town is in a snow belt (highest ground snow load in an occupied town in NH) at 110 PSF. The latitude is roughly 45 degrees so there is quite a difference in summer and winter optimum angles. Vermont several years ago put in an incentive system to encourage locally built equipment effectively ghost written by a company that happened to be coming out with multiaxis tracking collectors so the incentives were focused on trackers. if you search for All Earth Renewable they will pop up. They definitely are the status symbol in VT. In NH they make little of no sense due to the substantial added cost for the tracker with no targeted incentives but the local solar guy has installed several locally in Northern NH, presumably for people with more money than common sense.. This summer I noticed a new foundation installed in the small yard of a summer residence and about 2 months ago a 4 KW tracking array was installed. its a small lot facing south but the house roof really wasn't suitable for a big array and given its age my bet is the roof structure is undersized so no option of adding them to the roof. There was room for ground mounts but instead they put the foundation in what looks to be the minimum set back from the road. With the array mounted and it rotated out in an arc it almost looks like someone could touch it when they drive by, So chalk one up for a conspicuous install. I think the term "one that only a mother could love might apply". They look good in a farm field but next to a small home on a tight lot the proportions are jarring.

    its been a very mild winter with minimal snow up until a week ago. We had several days of snow and it totaled up to 16" possibly. The thing most folks don't factor in is with slated arrays the snow still falls on them and it either initially slides down in front of the array and forms a mound or on occasion it builds up on the array and then slumps off all in one shot forming a well packed mound that rapidly gets hard.. The tracking arrays have various preprogramed responses to unusual conditions. if they are covered with snow they tilt full vertical and track until the snow slumps off, If its too windy an anemometer has a high winds setpoint and the array goes horizontal to cut down on sail area. I am unsure what it does if its windy and snowing but I think it goes horizontal and then at some point when the wind drops it goes vertical to clear the accumulation. Folks would assume the wind would scour the snow off but not always if its sticky. In theory these have been sold in snowy Vermont for years but in this town there is an identical unit that seems to be left in one position all winter. Sixteen inches of snow on the ground is not much for winter in Northern NH. Many winters I will get four feet of snow in my front yard and have seen 6'. I have a pole mount array that was originally designed for snow clearance but at one point I swapped out the panels for larger ones so my snow clearance at winter angle is about 30" I have a snow blower and usually run the snowblower in front of the array while cleaning up after a storm and that deals with any snow that slides down. So the other day I am driving down the road past this lot and what do I see?, a tracking array stuck in a lump of snow at an odd rotation angle somewhere in the early morning angle. My guess is the array woke up after windy night, detected snow build up and rotated vertical until the snow slumped off and it built up a mound of snow higher than the lower edge of the array. My guess is the array has at best 3' of clearance in winter on each side at its centerline but when the array is rotated 90 degrees to the sun the top edge is is closer to 2' its on slope so at noon the array probably has 4' plus at noon.

    Running a snowblower in front of this 4 KW beast may not be easy, its on sloped lot and its not just one strip that needs clearing it pretty well the entire tracking radius. I am not sure if the owner is home but at some point I expect there will be an interesting phone call or two. The town is also in high wind zone so I dont know if they could add in a spacer to raise the array. Its not something that would be easy to guy as the array sweeps quite an arc. Most of the summer folks are gone for the winter so except for the locals the embarrassment is minimal. My guess is they will fix the array at one angle for the winter and then start it tracking again in April when the snow pack melts and the summer folks start returning. At least they will get some extra output in the summer for their investment.


  • #2
    I hate it when this happens - about an inch of snow. Whole town of flatlanders have gone nuts, cars off the side of the road, accidents.
    So I just run the generator and wait for it to warm again.
    Powerfab top of pole PV mount (2) | 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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      I completely agree that this was poorly engineered.

      Perhaps some would say that our presence on this discussion forum means that we are too detail conscious. "You expect things to work? You must be a real geek."

      I sure hope that the artificial intelligence (???) in the controller didn't keep trying and burn out their motors or drivers. That kind of design error is inconceivable...or is it?

      peakbagger wrote: "My guess is the array woke up after windy night, detected snow build up and rotated vertical until the snow slumped off and it built up a mound of snow higher than the lower edge of the array."

      If the system is grid-tied, it should always have power, so it won't need to have daylight to wake up. But it can still get overwhelmed when snow slides off.

      I've experienced the avalanche from my roof array onto my driveway. It makes a high, dense pile that I can't simply blow away. Fortunately, so far, I've always been able to chop it into reasonable pieces with a vertical shovel then clear it with the snowblower. However, if we get a massive wet snowstorm that freezes, I may not be so lucky.
      7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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      • #4
        I hate it when snow happens. pic shows 0.5", now we are at 2"
        update - ended up with 3" of wet slushy snow, and hazy sun is starting to melt it off

        20210126_144431.png
        Last edited by Mike90250; 01-27-2021, 03:27 PM.
        Powerfab top of pole PV mount (2) | 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

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          I agree that "wake up" is bad term. I havent spent a lot of time looking at these arrays at night but I think they travel back to its morning starting point overnight and then park until the predicted sunrise occurs. The All Earths are not technically trackers, I think they follow a calculated arc versus using a differential sensor to always keep it pointed in the right direction. They claim GPS enabled but my guess is all the GPS signal is doing is giving them a accurate time base and a lat/long to pick the right arc.to travel in.

          My guess is from liability point of view that there is torque sensor to lock out the drive if it encounters an obstruction.

          Comment


          • #6
            I went by the tracker this morning after 12" of snow yesterday. It had managed to scrape the snow away as the snow settled prior to the storm but this morning its buried along the entire lower edge facing North North East. My guess is it will be that way for another 5 or 6 weeks unless we have warm up. The early summer folks that they need to impress do not usually show up until late April when the snow pack is gone so other than a few months of lost net metering they should be all set.

            Comment


            • #7
              I drove by and the snow is melted but the unit is no longer tracking. I also noticed that the dealer that I thin installed it cleared out of town. I was also looking at another similar model that has been fixed in one location for a couple of years. Looks like whomever built the foundation did not take into account frost. The entire pole is tilted about 5 degrees and someone has piled up rocks around the pole which I guess is an attempt to keep it from tilting farther

              Comment


              • #8
                I keep looking for ideas, but in truth most amateur PV solar systems I see locally
                and on the internet, are fair weather machines. Fine in the desert, but can solar
                work in the snow latitudes?

                Some build toy arrays, but I wanted to do something significant, like eliminate any
                monthly paying homage to the gas company, when serious heat is only needed a
                few months of the year. My installer put up the same type array as all the rest, no
                allowances for clouds, rain, snow, or line voltage.

                Over and over I see 3, 4, or 5 rows of panels stacked up with no gaps. Dragging
                that much snow that much distance to the bottom, is extremely difficult and more
                likely does not get done. Then the snow forms a huge pile at the bottom, which
                must be cleared away. Building with gaps between panels drastically cut the amount
                of snow being moved at a time, and the distance it must be moved. Then, much
                snow drops thru behind the array, and never needs to be cleared from the ground.
                AND, the bottom needs to be high enough to be clear of the snow pile.

                Tilting the array twice a year can improve production and drastically reduce snow
                accumulation. Few even consider this, other so called tilt bearings are just a bolt or
                pipes, holding metal surfaces together that will not be so able to pivot after a few
                years outdoors. If the array is not near balanced, moving it will be a huge and likely
                dangerous project.

                This is not rocket science.

                On the other hand, all sorts of resources are spent in less than productive ways. I
                constantly see micro inverters used where string inverters would be more efficient
                and use a lot less wire to get the job done. Micros are no brainers, which means no
                opportunity will occur to do anything clever, but there will be near infinite data to be
                viewed to see if every last panel is perfect. Over a hundred panels have been in
                service here nearly 8 years with not a single failure, wiring has been much more of
                a problem. Even those rare issues are dealt with using very little brain or equipment.

                And arrays are built perfectly level, as if the sun cared. I saw one end of an array 15
                feet off the ground just to make it level, yards and tons of dirt often moved. I guess
                nobody knows how to deal with an angle, tools exist. My ground is on a 10% grade,
                and so is the array.

                I see any combination of wood. steel, aluminum, along with any type of hardware
                bolted together, not likely to ever come apart in the future, what about corrosion
                and rust? Foundations are all over the map. Everyone is in a hurry to just use
                clips sliding in slots, to avoid any kind of precision work. No clips or slots here.
                Bruce Roe

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