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  • #16
    Originally posted by Jest Waitn View Post

    ok. that's what i thought - south facing.

    i have found no proof that the poco sets the maximum pv scaling level, so i have challenged this because i believe that the rep is either misinformed or is trying to 'cap' system sizes. the PSC sets the standards and i found nothing anywhere, including the administrative code (law) that states caps on the production, bar that the system '[SIZE=2]Does not exceed 90% of the customer
    several pocos do cap for access to net metering. check with the poco and look for the net metering application documents.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #17
      Originally posted by ButchDeal View Post

      several pocos do cap for access to net metering. check with the poco and look for the net metering application documents.
      i have not seen this in the application. i asked the rep to show me 'the language' since he offered in the first place.

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      • #18
        Originally posted by bcroe View Post
        Here there is no restriction on plant size, just varying regs. The E-S-W panels allow a smaller inverter plant
        if that matters. Facing S only will allow somewhat fewer panels at the expense of a larger inverter plant,
        since your energy all comes in a big lump. But clouds are a big incentive here; your results may vary. Bruce Roe
        clouds really cut down on production here also. almost the entire month of june was cloudy. july has not been as cloudy so far.

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        • #19
          Originally posted by bcroe View Post
          Here there is no restriction on plant size, just varying regs. The E-S-W panels allow a smaller inverter plant
          if that matters. Facing S only will allow somewhat fewer panels at the expense of a larger inverter plant,
          since your energy all comes in a big lump. But clouds are a big incentive here; your results may vary. Bruce Roe
          inverters are no problem. got a deal on 2 awesome fronius 5kw before the rep told me there was a cap on system size.

          Comment


          • #20
            Originally posted by ButchDeal View Post

            Since you are limited in total size based on DC capacity your best return is going to be south facing unless there is some time of use.
            +1. All other application and location particulars being the same, face them south for best/most bang for the buck.

            Unless something strange is going on with the annual insolation on an array, like a major obstruction to the south, and all other things being equal, for the same location, screwing around with east or west orientations on a grid tie system will always be less cost effective than a south (or equator facing) or mostly south facing array. Bruce has this idea that spreading out production over a day using off south orientations is better for some reason having to do with inverter cost or maybe some other stuff. I respectfully disagree. For east-west vs. all south arrays, east-west will require more panels (probably ~ 10-20% depending on lat. and tilt) for the same annual production as south facing. That extra cost of the equipment in panels, wiring, BOS equipment and labor will not be covered by any inverter savings realized as a result of enabling smaller inverters to be used.

            As for larger arrays producing more under cloudy skies - they sure do, probably is some direct proportion to the array size ratios. But, the amount of annual production under cloudy skies is so small, even in very cloudy parts of the U.S., that upsizing an array to get more of what's already a small quantity is a waste of resources and cost ineffective. Also, and considering equal size arrays, the amount of annual insolation reaching a south facing array will be either the same, or, depending on the diffuse insolation model used, either equal to or, slightly more than the insolation reaching a non south facing array.

            As for off south orientation with respect to T.O.U tariffs, care is usually very necessary, particularly when considering that NEM rates will likely always be changing as will, and equally or more importantly, peak tariff time(s). Right now, for example, in southern CA, Peak T.O.U. tariff times are mostly mid-late afternoon, M-F. That makes the CURRENT optimum orientation to produce the most array revenue offset about 190-205 deg. +/- a bit and a tilt of ~~ local lat. +/- acouple of degrees or so. For (most) homes around here (that is, with fixed orientations), and in spite of what might be kindly referred to as confusion being spread by the POCOs and PV peddlers to help themselves with the duck curve, or sell more product respectively, south is a more cost effective orientation than west - AT THIS TIME. Once T.O.U. peak times change to later in the day, as they will, that south orientation pricing advantage will decrease and, if peak times or the rest of the rate differentials changes enough, a west orientation may become more cost effective. I suspect other areas have similar logic.

            For optimum or better orientations under T.O.U., if under a true T.O.U. tariff (that is, one that does not have tiers overlayed in it) I've found one good way to treat PV arrays is both as electrical generation facilities and revenue producers. That is, for grid tied arrays, get the array production estimate in kWh/yr. for all orientations being considered, and use the tariff that the array will be working under to produce an annual revenue estimate without considering usage or the cost of usage, which is treated separately (Under this scenario, the revenue a fixed array produces under a simple tariff will not be affected by the electric bill). Do that for all orientations under consideration and compare revenues. The orientation that produce the most revenue wins. That method works quite well for my POCO's T.O.U. residential tariff for homes with a PV system (DR-SES). Maybe Sensij can critique the idea/method.
            Last edited by J.P.M.; 07-11-2017, 01:18 AM.

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            • #21
              Originally posted by J.P.M. View Post

              +1. All other application and location particulars being the same, face them south for best/most bang for the buck.

              Unless something strange is going on with the annual insolation on an array, like a major obstruction to the south, and all other things being equal, for the same location, screwing around with east or west orientations on a grid tie system will always be less cost effective than a south (or equator facing) or mostly south facing array. Bruce has this idea that spreading out production over a day using off south orientations is better for some reason having to do with inverter cost or maybe some other stuff. I respectfully disagree. For east-west vs. all south arrays, east-west will require more panels (probably ~ 10-20% depending on lat. and tilt) for the same annual production as south facing. That extra cost of the equipment in panels, wiring, BOS equipment and labor will not be covered by any inverter savings realized as a result of enabling smaller inverters to be used.

              As for off south orientation with respect to T.O.U tariffs, care is usually very necessary, particularly when considering that NEM rates will likely always be changing as will, and equally or more importantly, peak tariff time(s). Right now, for example, in southern CA, Peak T.O.U. tariff times are mostly mid-late afternoon, M-F. That makes the CURRENT optimum orientation to produce the most array revenue offset about 190-205 deg. +/- a bit and a tilt of ~~ local lat. +/- acouple of degrees or so. For (most) homes around here (that is, with fixed orientations), and in spite of what might be kindly referred to as confusion being spread by the POCOs and PV peddlers to help themselves with the duck curve, or sell more product respectively, south is a more cost effective orientation than west - AT THIS TIME. Once T.O.U. peak times change to later in the day, as they will, that south orientation pricing advantage will decrease and, if peak times or the rest of the rate differentials changes enough, a west orientation may become more cost effective. I suspect other areas have similar logic.
              ok. thanks.

              fortunately this poco has no TOU tariffs. basically for the 1st 1000kwh usage the rate is ~ 9 cents/kwh; after this the rate is ~ 11 cents/kwh.

              anyone seen this (E/W vs. N)?

              https://www.gses.com.au/wp-content/u...est-arrays.pdf

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              • #22
                Originally posted by Jest Waitn View Post
                That paper is written for an Australian audience. They are in the southern hemisphere, so in the same way that south facing is best for us, north facing is best for them. Describing the optimum as equatorial facing would be universal (or just planetary, I guess), but since most of the forum discussions are related to the northern hemisphere, when I shortcut to "south is best", it means I don't have to assume the person reading it understands what "equatorial" means.

                Note that they conclude E/W had a 15% penalty in their example, about the same as what you would find just running PVWatts.

                I've got nothing to critique with J.P.M.'s suggested method of finding optimum orientation on pure TOU plans by maximizing revenue, he was way ahead of the curve around here in advocating that way of thinking about it. As plans become more complicated, our tools for evaluating them will inevitably follow.
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                • #23
                  Originally posted by Jest Waitn View Post
                  That is in Australia so it would be for you E/W vs S
                  Bcroe has already given you the benefits of E/W which would be more for an off grid system or one with some limitation. Your PoCo doesn't have a limitation so you are better off with south.
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                  Comment


                  • #24
                    Originally posted by Jest Waitn View Post

                    ok. thanks.

                    fortunately this poco has no TOU tariffs. basically for the 1st 1000kwh usage the rate is ~ 9 cents/kwh; after this the rate is ~ 11 cents/kwh.

                    anyone seen this (E/W vs. N)?

                    https://www.gses.com.au/wp-content/u...est-arrays.pdf
                    Based on an earlier post you mentioned "florida/florida" so should I presume you are in Florida and it is one of their POCO's you are talking about?

                    Based on FPL solar net metering process they indicate a max of 115% of the AC kWh used in a year. Once you have determined your average AC kWh yearly usage you multiply that by 115%. Now divide that number by 0.85 to get the max DC wattage of the system.

                    They also mention 3 Tiers which is associated with the system size. T1 is 1kw to 10kw. T2 is 10kw to 100kw and T3 is 100kw to 200kw which I presume would be for a commercial installation.
                    Last edited by SunEagle; 07-11-2017, 11:19 AM. Reason: correctly my math

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                    • #25
                      Originally posted by Jest Waitn View Post

                      clouds really cut down on production here also. almost the entire month of june was cloudy. july
                      has not been as cloudy so far.
                      Every situation will be different. The thing that most impresses me about this system, is its ability
                      to produce a lot of power (though reduced) under various levels of clouds. I have seen it delivering
                      4 KW in pouring rain. Light clouds hardly affect output. We have gone 4 weeks in a row in Dec
                      without ever seeing the sun, but even with the short days the system delivered about 1/3 the
                      summer peak energy.

                      Another thing that happens A LOT here, is weather changing mid day. We will often see strong
                      clear sun at sunrise, but approaching midday clouds will roll in. Some days it happens in reverse.
                      South only panels will leave a system with not much to do. WHATEVER time the sun is strong,
                      this system will capitalize on it.

                      So I see the E-S-W panel approach as much more attractive under frequently cloudy weather.
                      Making power under clouds will always cost more, so it can't be economically compared directly
                      to cloudless SW desert performance. The version in the picture worked well as much by luck, as
                      precise planning; 4 years of field time with a clamp on DC ammeter revealed much. The next
                      alignment iteration will do even better (I hope).

                      Remember, the once exotic panels have become a small fraction of the system cost. Getting
                      your power evenly over time, instead of in a big lump, has advantages. Your situation will be
                      different from mine. Bruce Roe
                      Last edited by bcroe; 07-11-2017, 11:09 AM.

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                      • #26
                        bcroe , inverter limitations aside, if your panels were all south facing, you would produce even more energy than what you get with the east/west array. If you had the ability to chart exactly how much energy each orientation of your system produces over a year, it would be obvious to you.
                        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                        Comment


                        • #27
                          Originally posted by bcroe View Post
                          The E-S-W panels allow a smaller inverter plant if that matters.
                          Bruce I am new here can you point me in the direction of how your panels are wired to the inverter?

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                          • #28
                            Originally posted by sensij View Post
                            bcroe , inverter limitations aside, if your panels were all south facing, you would produce even more energy than what you get with the east/west array. If you had the ability to chart exactly how much energy each orientation of your system produces over a year, it would be obvious to you.
                            YES, inverter limitations aside. But with 75% of my investment in the inverter plant, that isn't a practical
                            approach. I got to watch the initial S system doing nothing much of the time; I am not anxious to double
                            the size of the inverter plant and watch THAT investment doing nothing. In any case doubling the inverter
                            plant capacity would be quite difficult in my situation. Remember the high line voltage shutdown problem;
                            there are 4 more compelling reasons at this location not to use more inverter capacity.

                            Your situation will vary. Bruce Roe

                            Comment


                            • #29
                              Originally posted by wienerdog View Post

                              Bruce I am new here can you point me in the direction of how your panels are wired to the inverter?
                              Simple string inverters are used here. There are multiple strings of panels connected in parallel to
                              an inverter. All the panels in a string have the same orientation, but a roughly equal number of
                              those strings face E, S, or W. So at sunrise most power comes from the E strings; that diminishes
                              as the sun moves to produce maximum power from the S panels, and so on through sunset.

                              The idea is to try and balance an even amount of power over the day by number of panels, tilt,
                              etc. Over the seasons this is only roughly achieved. Don't think that the panels facing away from
                              good sun are producing zero; my clamp on DC ammeter says otherwise.

                              Bruce Roe

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                              • #30
                                Originally posted by SunEagle View Post

                                Based on an earlier post you mentioned "florida/florida" so should I presume you are in Florida and it is one of their POCO's you are talking about?

                                Based on FPL solar net metering process they indicate a max of 115% of the AC kWh used in a year. Once you have determined your average AC kWh yearly usage you multiply that by 115%. Now divide that number by 0.85 to get the max DC wattage of the system.

                                They also mention 3 Tiers which is associated with the system size. T1 is 1kw to 10kw. T2 is 10kw to 100kw and T3 is 100kw to 200kw which I presume would be for a commercial installation.
                                what i said is the following: "a method is actually used, that's not a %, but that arrives at a %. florida/florida power. the calculation used was based on 8269 kwhac. so the result is 7.1 kwdc = (85.9% * 8269). but for this to be 'true' it has to be stated and i can't find it, so i have asked to see this in print.

                                the method is to take annual kwh, multiply it by 115 and then divide the result by 1135. which yields 7.1kwdc for the maximum array. the present array size is 3460wdc.
                                "

                                i live in florida and florida power is the poco. the rep said to multiply annual usage by 115 and divide the result by 1135. these are stated in the post.

                                btw, dividing the result by .85 would result in an enormous number!

                                anyway, where have you found max 115% stated by florida power?

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