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  • #31
    ... truncated post on Android 6.0 with the degree special symbol ...
    ... Preview seems to work ...

    Putting panels on the North half of the roof , they also can circumvent these feed-in cuts ,
    like a 20 kWp generator on both roof halves would be allowed to deliver 14 kW ,
    while a 10 kWp generator would be allowed to provide just 7 kW , if restricted to 70% .

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    • #32
      Originally posted by Yet another Yeti
      What about the performances during weeks of 100% clouded skies , like we have in the North during December ?
      Is there really a measureable intake and output , that is worth to keep the solar generator in operation , or would
      it not really matter to shut it down during the winter solstice weeks ?
      People in Germany start to put solar panels on the north side , if the angle of the roof is low as less than 20
      Do what you want, my panels deliver power every day of the year (by design). Today I went to the compost bin and
      noted clouds were so heavy I could not see any shadows. I peeked in the shed and 15KW of inverters were delivering
      10.5KW. They do it by a gross DC to AC factor, but with varied orientation generate power all day under sun with very
      little clipping at any time. Bruce Roe

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      • #33
        Originally posted by Yet another Yeti View Post
        What about the performances during weeks of 100% clouded skies , like we have in the North during December ?

        Is there really a measureable intake and output , that is worth to keep the solar generator in operation , or would
        it not really matter to shut it down during the winter solstice weeks ?

        People in Germany start to put solar panels on the north side , if the angle of the roof is low as less than 20
        First of all, even with skies completely cloud covered, about 10% - 30 % of the above the atmosphere solar energy still reaches the ground. Google "Clearness Index" for details and begin a real education.

        While resource availability is more limited and thus output is decreased during winter months, it is still measurable and useful. To answer your own question about resource availability, run PV Watts for places like Lansing MI, or Buffalo, NY (the latter where I lived for ~ the first half century of my life and also cut my solar energy teeth), two of the worst solar winter climates in the U.S.

        The 4 winter months (N,D,J,F) in those locations, while not real good, still produce ~ 20 - 25 % of a years total PV output. Takes a little more maint. and a bit more thoughtfulness in the design to pull off an installation, and it isn't as easy to make PV cost effective, but shutting off an adequately designed array in the winter is shooting yourself in the foot.

        As for putting panels at an azimuth facing away from the equator, it's simply a dumb idea. For starters, it's almost never even remotely cost effective. It's also effectively limiting resource availability. It's about the worst possible array azimuth. The installation cost would need to be lower than currently possible by a lot to improve the economics to the point of cost effectiveness. Anyway, even if the installation was free, the space requirements to meet a duty would preclude many, if not most applications.

        As Bruce writes, everyone is entitled to an opinion. Mine opinion is your opinion is ignorant with respect to solar energy and its advantages and limitations. You need an education. Start with the basics. Suit yourself, but you're spinning your wheels without it.

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        • #34
          Originally posted by J.P.M. View Post
          ...........
          As for putting panels at an azimuth facing away from the equator, it's simply a dumb idea. ..........

          As Bruce writes, everyone is entitled to an opinion. ........
          Not such a dumb idea if your goal is to optimize site or system efficiency as bcroe has explained at length through out this forum. I tend to agree with Bruce's opinions more that those of J.P.M.

          Your decision should relate to your goals. If they are just financial then follow the advice of J.P.M. If your goals are more holistic then set your goals accordingly to optimize your results.
          9 kW solar, 42kWh LFP storage. EV owner since 2012

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          • #35
            Originally posted by Ampster View Post
            Not such a dumb idea if your goal is to optimize site or system efficiency as bcroe has explained at length through out this forum. I tend to agree with Bruce's opinions more that those of J.P.M.

            Your decision should relate to your goals. If they are just financial then follow the advice of J.P.M. If your goals are more holistic then set your goals accordingly to optimize your results.
            I also agree with Bruce more than I agree with you.

            If we keep this up, we may actually find more to agree about and stop sniping at one another.

            I'm not speaking for Bruce, but it seems he and I have similar goals in that not all of what we do is oriented toward the bottom line. Seems to me we're different than a lot of PV owners in the respect that cost is not the always the primary motivator in what we do and why we do it.

            As for goals, I absolutely agree with you. To that end, I've observed and I'll continue to put my faith in the almost universal idea that most people have more parochial concerns for their finances than most anything else. To the degree that's a reality, optimizing the cost effectiveness of an array becomes a reality and the goal you write of that most folks have - often to the exclusion of just about every other goal. Realizing that goal (most bang for the long term buck is another way to express it) usually (but admittedly not always - just most every time) means the simplest arrangement of fit for purpose equipment in an orientation (and sometimes but rarely more than one) that maximizes the annual solar flux (insolation) on an array. Just like a gas glut lowers the cost of filling up, maximizing the fuel availability (the solar flux) makes it cheaper to obtain - funny how that works out. That results in the best chance for the highest cost effectiveness which minimizes the LCOE of an application, with LCOE type of life cycle cost analysis being one common way costs are optimized and system options compared.

            At the end of the analysis, most PV go/no go decisions on residential grid tied PV, and probably a whole lot of the rest of the applications as well, are financial. No more. No less.
            Last edited by J.P.M.; 02-27-2019, 01:28 AM.

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            • #36
              Originally posted by J.P.M. View Post

              ....... the simplest arrangement of fit for purpose equipment in an orientation (and sometimes but rarely more than one) that maximizes the annual solar flux (insolation) on an array. ........
              Yes the simplest arrangement is to maximize the insolation on an array. That is a focus on just the array. My view is that in some situations a system approach to optimize the production from a site may be preferable. That could mean several arrays that keep the inverter producing power longer.
              For example when solar panels were more expensive, tracking arrays were popular. Today a good system designer might use more panels in different orientations as Bruce did to get a more cost effective result than a tracking array. Essentially this could result in a system with a high DC to AC ratio but with no clipping. What occurs is that a system with multiple orientations can collect more energy in the morning and afternoon. None of the arrays may be running at optimum the entire day but the site will collect more energy than it could from a single fixed array oriented due south at correct angle to the sun.
              Last edited by Ampster; 02-27-2019, 08:59 AM.
              9 kW solar, 42kWh LFP storage. EV owner since 2012

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              • #37
                Just keep in mind, solar design here is driven by the ever present clouds. Keep
                those inverters busy any daytime, any sky. Bruce Roe

                Comment


                • #38
                  Originally posted by bcroe View Post
                  Just keep in mind, solar design here is driven by the ever present clouds. Keep
                  those inverters busy any daytime, any sky. Bruce Roe
                  Thank you for mentioning clouds. I didn't think of clouds but they are another factor to take into consideration based on location. In my neck of the woods we have many micro climates. There is one area that gets a lot of overcast days because of the marine layer. Not many grapes grown in that area but it has been known as the egg basket of the world. They still have an annual Butter and Egg Festival and Parade. LOL Five miles north at an equal distance from the ocean there is a lot more insolation.
                  To the point of the topic of this thread, I would expect to see a variety of DC to AC ratios if system designs actually took the above factors into consideration.
                  Last edited by Ampster; 02-27-2019, 12:25 PM.
                  9 kW solar, 42kWh LFP storage. EV owner since 2012

                  Comment


                  • #39
                    Originally posted by Ampster View Post

                    Yes the simplest arrangement is to maximize the insolation on an array. That is a focus on just the array. My view is that in some situations a system approach to optimize the production from a site may be preferable. That could mean several arrays that keep the inverter producing power longer.
                    For example when solar panels were more expensive, tracking arrays were popular. Today a good system designer might use more panels in different orientations as Bruce did to get a more cost effective result than a tracking array. Essentially this could result in a system with a high DC to AC ratio but with no clipping. What occurs is that a system with multiple orientations can collect more energy in the morning and afternoon. None of the arrays may be running at optimum the entire day but the site will collect more energy than it could from a single fixed array oriented due south at correct angle to the sun.
                    After safety, my usual focus is to first maximize annual insolation on an array as that will, with all other things being equal will minimize the LOCE.

                    But, I know that good design always involves compromises and tradeoffs. But, I've found that for most design situations, Solar and otherwise, if I start with the most cost effective design and modify as necessary, I have a better chance of winding up with the best overall AND most cost effective design sooner.

                    Reality is, between 2 designs that are nominally and equally fit for purpose, the one that's more cost effective of the two will be the one chosen.

                    I must say that I'm perplexed by so much emphasis placed by some on maintaining a flatter production curve over maximizing production under a more rounded production curve. Maybe I'm myopic in my reading, but it seems like the idea of maximizing a system's capacity or utilization factor gets overlooked in the quest for a flatter production curve.

                    By my experience and observation as well as training, A system's components and their match up are a set of tradeoffs. What I see with the flatter production curve quest is a search for orientation(s) that maximizes an inverter's capacity factor, usually over a (theoretical) sunny day, often with little to no regard for the efficiency or cost effectiveness of the rest of the components and so the entire system. Put another way, doing so is a bit like throwing the baby out with the bath water.

                    To be clear, I'm not. and never have been against any array orientation or arrangement or size as long as it's safe. Beyond that, I agree that there are situations and applications where more than one array and so probably orientation may be more cost effective (and by that, to be clear, I mean lowest LCOE) than one single orientation that maximizes annual insolation on an array.

                    But as a design philosophy, I'll start with the orientation and arrangement that maximizes annual insolation and modify as the rest of the design parameters, constraints and owner goals dictate. That way, I'll usually drift less from cost effectiveness for the entire design rather than consider it as an afterthought and go fishing around for tweaks to squeeze a few more pennies out of an LCOE that could have been dealt with as a check at the last design iteration before sign off.

                    I also understand that the lowest LCOE may be the only consideration (FWW, I site my own array as an example). But, I'm of the strong opinion that most folks with grid tied systems have cost effectiveness as the primary requirement for a system. To the degree that may be true, most users will have the best shot at the most cost effective system with an array that maximizes, to the greatest extent possible, the annual insolation on an array with a single orientation.

                    FWIW, T.O.U. may have some modifying influence on that orientation. However, as best as I've been able to find (so far and at current T.O.U. rates and times, in CA anyway), optimum azimuthal orientation tends to shift about 20-25 deg. to the west of the max. annual insolation orientation where the figure of merit is the value of the electricity produced by the array to offset a charges for electricity per installed STC kW of PV. But I found that after I started with the max. solar flux orientation and wound up with a set of bill offsets for varying orientations.

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                    • #40
                      It is not the flatness of the curve that I was discussing. It is the area under the curve that needs to be considered when optimizing the site. . We are talking past each other. I agree with what you are saying when you are talking about arrays; All I am saying is that sometimes limitations of the site or other goals might suggest a look outside that box. Your example of a change in azimuth to account for a different reimbursement rate is one example of what I am talking about. I do not think we are that far apart. Certainly a fixed array mounted to the optimal tilt and azimuth is the correct starting point. One only has to look at the acres of desert production facilities that are built on that premise.
                      9 kW solar, 42kWh LFP storage. EV owner since 2012

                      Comment


                      • #41
                        Originally posted by Ampster View Post
                        It is not the flatness of the curve that I was discussing. It is the area under the curve that needs to be considered when optimizing the site. . We are talking past each other. I agree with what you are saying when you are talking about arrays; All I am saying is that sometimes limitations of the site or other goals might suggest a look outside that box. Your example of a change in azimuth to account for a different reimbursement rate is one example of what I am talking about. I do not think we are that far apart. Certainly a fixed array mounted to the optimal tilt and azimuth is the correct starting point. One only has to look at the acres of desert production facilities that are built on that premise.
                        I don't think you're talking past me, but somehow I'm not getting through. I've already written all that.

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                        • #42
                          Just an update, after a couple more conversations with my installer they have agreed to come out and swap out my 10kw converter for the 11.4kw, no charge. This is for my 12.96kW system. They say it will only produce 150 more kWh's per year, an amount I'm not sure I believe, but at zero cost the payback is immediate. It was information I received here that managed to make this happen. He realized I had done some homework!

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                          • #43
                            Originally posted by Alan1296 View Post
                            Just an update, after a couple more conversations with my installer they have agreed to come out and swap out my 10kw converter for the 11.4kw, no charge. This is for my 12.96kW system. They say it will only produce 150 more kWh's per year, an amount I'm not sure I believe, but at zero cost the payback is immediate. It was information I received here that managed to make this happen. He realized I had done some homework!
                            Here are two graphs from my 11.25 kW system on my SE7600 inverter in March 28, 2018 and March 29, 2019 with them adding an additional inverter. They were supposed to just add a SE3800 inverter with EV charger to stop the clipping, but they brought the wrong one and just installed a second SE7600... Over 7 kW would have been probably been clipped since the March 28, 2018 was a better solar day as well.
                            Attached Files

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                            • #44
                              Interesting. Why wouldn't they just order the correct SE3800? The company that hooked up my new 11.4 said that the inverter was a brand new model so they don't even have a compatible antenna. So I've been without anyway to monitor the system for three weeks and another two more weeks before they get me an antenna that works. This new inverter has no display so without the connection I have no way to know what it's producing. I'm looking forward to seeing some graphs again here in a couple weeks.

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