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PV panel orientation?

Discussion in 'Environmental Discussion' started by mwalsh, Jul 14, 2010.

  1. mwalsh

    mwalsh Member

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    Do any of you have PV systems where the panels sit at different orientations? How did your installer handle it:

    a) One single tracker inverter.
    b) One multi-tracker inverter.
    c) Two single tracker inverters, one for each orientation.
    d) No clue.
     
  2. icarus

    icarus Senior Member

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    First, I would visit: Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun - Powered by vBulletin

    Second, I would never use just one inverter if the panel orientation was significantly different, as you would throw away a considerable potential harvest, depending on the array size.

    I know that Drees is very happy with his Enphase micro inverter system, I personally would prefer central inverters but the Enphase has a place.
     
  3. hill

    hill High Fiber Member

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    Different orientation like this?

    [​IMG]

    One side of panels (16 total) face East/North east while the other side (20 total) face South/south west. There is a separat 4Kwh (ac) inverter for each side. Configured this way, we probably loose about 15% total efficiency but we're tight on space so it's the best we can do.
     
  4. mwalsh

    mwalsh Member

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    Thanks, I'm already dipping my toe in the water over there. :)

    The vendor is fundamentally opposed to micro inverters on the basis of introducing multiple potential sources of failure and his reckoning that in the not too distant future micro-inverters will be built into panels, making separate ones obsolete and difficult to obtain replacements for.

    With a single inverter and strings in different orientations, can you guys help me understand what happens when they are corrected in series......am I correct in thinking that performance of the entire array diminishes to that of the worst performing string? This is what I'm worried about most. I get some really nice sun on the south facing roof at a time when I'm worried significant shadowing will fall on the panels to the east (though I must say that I have yet to go up on the roof late in the day to see what actually happens).
     
  5. KK6PD

    KK6PD _ . _ . / _ _ . _

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    I did my own installation, 3 2500 watt inverters, 60 solar panels. On a combination flat, and pitched roof. Planning is critical, and if you do your homework you can achieve a really good system!!!
     
  6. icarus

    icarus Senior Member

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    Within certain limitation, partial shading, even from a wire for example will reduce the output of the entire series string. I do understand your installers point of view given multiple points of failure, but clearly you have to decide where the trade off is.

    I suggest you post the same question on the Solar forum, grid tie section. There are a lot of very smart folks over there who are designers/EE's etc who have seen it all.

    Icarus
     
  7. mwalsh

    mwalsh Member

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    After reading up some on the micro-inverters, I think that's what I'm going to insist on. It just seems like the most elegant solution for my particular situation.
     
  8. drees

    drees Senior Member

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    Got some pics? Love to see PV installs.

    I'm sure mwalsh won't mind me intruding on his thread since I already provided advice on the two other forums he posted on. :)
     
  9. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Here is an aerial shot from Bing...

    Bing Maps

    Zoom in, my house is the one with 3 sat dishes, and the white roof......

    and the Solar, and ...Pool Heating panels....

    Can't see the pool?
    It's indoors.... SWEET!!!
     
  10. drees

    drees Senior Member

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    Nice setup! That's a lot of solar panels! How many kWh do you generate a year? I'm guessing over 10,000?
     
  11. hill

    hill High Fiber Member

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    Now THEM is mighty big sat dishes. Either that, or the worlds largest wok. You could cook a lot of rice in a wok that big. Or maybe use 'em for moon bounce on the ham bands.
    ;)

    .
     
  12. JeffreyDV

    JeffreyDV New Member

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    My panel/inverter orientation is as follows:

    Array 1: orientation- East, 18 216 Watt panels, one 3500 Watt PV Powered inverter.

    Array 2: orientation- West, 27 216 Watt panels, one 4800 Watt PV Powered inverter.

    This system has been in service for 1 year and covers almost my entire electric usage.
     
  13. jcgee88

    jcgee88 Member

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    Disclosure: I installed Enphase micro-inverters on my
    PV array, which consists of two different facets.

    I think that it is ironic that your contractor faults
    micro-inverters' "multiple sources of failure" as his
    rationale for not recommending them. Enphase touts
    their products' reliability as one of their main advantages
    over a string inverter. Enphase's logic is twofold: first
    if a string inverter fails, your whole array goes down,
    whereas with distributed inverters you only lose the one
    that failed; and second, a micro-inverter has to deal
    with a much lower electrical load (one panel's worth)
    than a central inverter and thus should be inherently
    more reliable.

    Enphase's white paper on micro-inverter reliability is here:

    http://www.enphaseenergy.com/downloads/Enphase_WhitePaper_Reliability_of_Enphase_Micro-inverters.pdf

    But the issue of reliability aside, the day to day
    benefit of micro-inverters is that you get the max
    harvest from each PV module, whereas a string inverter
    has to sync to the PV module that has the lowest
    output. That loss gets further multipled if you have
    any shading issues at all.

    In my own case, I am getting a 6% increased harvest
    on my "best case" facet (this is the difference in output
    between my west-most panel and my east most panel;
    the west-most "lights up" sooner), and a 7% increased
    harvest on my worst case facet (one panel has shading
    issue for a short time in early morning). There's
    probably some MPPT advantage as well, but I don't
    have a way to measure that.

    This same logic could be applied to current string
    inverters, too.

    --

    No one inverter solution is perfect for every situation.
    I think you are making a good decision to make your
    contractor consider micro-inverters for your situation
    based on the facts of your situation, and not on his
    comfort zone.
     
  14. icarus

    icarus Senior Member

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    For what it is worth a couple of thoughts: First, I would be surprised if "in the future inverters would be built into panels" The reason, as I see it is that PV panels have a great many potential configurations including DC outputs that would make built in inverters less useful to say the least.

    Second, If it were me, and I had consistent panel orientation I would go with a central inverter for two reasons. The first is the only single point of failure, in a package that is easy to replace. Additionally the track record of name brand inverters is pretty darn good. While I believe that Enphase is a real product and has a real future, in this business, failure of the business is not unheard of. What would you do, for example, if in ten years, you had a single (or multiple) inverter failure(s) and Enphase is no longer available? In a conventional failure, at least if brand X is out of business it is pretty likely that brand Y will be available. So in the case of a an Enphase failure you now would have to completely reconfigure your array, at considerable expense to bring the failed components on line.

    All that said, I would consider a Enphase system if my PV facets were significantly compromised and different, so that the Enphase system would significantly increase production.

    Just my thoughts, worth only the price you pay for them.
     
  15. jcgee88

    jcgee88 Member

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    If you have a consistent panel orientation, including
    no shading issues, then a string inverter's fixed cost
    becomes its big advantage for large arrays. With my 13
    panels, I was in a gray area, that is, a string inverter
    vs 13 Enphases cost in the same ballpark. For me,
    since the costs were about the same and they made
    up just 13% of the total cost anyways, my decision criteria
    then shifted to yield, that is, how to get the maximum
    value out of the remaining 87% of my investment.

    On the other hand, if we were talking about, say, 50
    panels, again assuming a consistent panel orientation, then
    one string inverter would be the far superior solution if
    cost was your decision criteria.

    With regard to reliability, this is more a discussion of
    future technology and warranty rather than actual
    product. In the near term of, say, 1-2 years, I figure
    that Enphase would be around to do direct 1 for 1
    replacement if an inverter would go bad. Once you
    go beyond a few years, it's unlikely Enphase would stock
    today's product for warranty purposes for long, after
    production had ceased. Electronic products go bad if you
    sit them on a shelf for years on end. So, keeping spares
    inventory of them is more expensive then just shipping
    an equivalent current product. I saw this during my
    tenure at a technology company (HP).

    This reminds me of the extended warranty I got with my
    first digital camera. The camera did go bad, and the
    vendor sent me a new one. Even though only one year
    had elapsed, the new camera was not the same model
    as the old camera, it was the then current "equivalent."
    I sense that the micro-inverter industry's maturity and
    rate of innovation is analogous.

    As to the possibility of Enphase not being around,
    this also can be said of any component - panels,
    inverter, software - that you have installed today.
    Even the biggest, most successful companies can
    and will exit a primary business (IBM doesn't make
    PC's anymore...though that's no great loss :). You
    just have to take it on faith that "someone" will be there
    two decades from now when you need a replacement
    part.
     
  16. icarus

    icarus Senior Member

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    Jut to hone my point a bit. Currently, there is only one choice of micro-inverters, Enphase. So if a number of them go TU in a few years and Enphase is TU, there is currently no viable replacement. The option then would be to rewire the entire string with a conventional inverter.

    On the other hand, if a conventional inverter fails, and it is out of business, there is currently a Brand X or Y or Z available to replace the bum one, without any rewire of the string.

    Like I said, I would consider micro-inverters given off axis array, but other than that I would use a conventional inverter system.
     
  17. mwalsh

    mwalsh Member

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    I've had another change of mind. Hopefully the last:

    18 x Sunpower 315 panels on the south facing roof with a single SB5000 inverter.

    So, yes, the Sunpower panels are probably going to be expensive. I have no idea what yet, but I'm hoping they're not mind numbingly so. Not cool of Sunpower to keep their pricing confidential so you don't really know what their panels should cost!

    But compared to 26 or 28 lesser output panels, plus a bunch of micro-inverters or a two-inverter system,...unless the cost is obscene or the panels are made of unobtainium, I think it might just be the way to go. Plus it might be easier to get these panels right now as government agencies and non-profits across CA cancel their orders because the incentives are on hold.

    I'm also sort of getting to the point now where I'm tired of thinking of this anymore. I've had like 7 or 8 solar guys through here, each trying to peddle their point of view as being the best, and none really offering the solution I want in terms of system size and/or configuration. Do you ever get to the point that you think maybe the right answer is just to do nothing? Like when you go to the store to buy clothes, but don't really find anything that suits you, so you leave empty handed....that's sort of where I'm getting to.
     
  18. icarus

    icarus Senior Member

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    My favorite response in the solar world is the best way to get the best system is to avoid the pitfalls of "Ready, fire, Aim!" Look at it this way. You may be tired of the process, but a few hours of aggravation now might yield a much better compromise in your system.

    I always suggest looking long and hard at all aspects of all options before you jump. This is a big money, long term deal, so make it as right as you can.

    Icarus
     
  19. jcgee88

    jcgee88 Member

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    In my mind, your desire to have one string, located in one
    somewhat constrained spot, having the large capacity you
    need...makes Sunpower a natural candidate. That being said,
    you should be aware that Sunpower is very picky about its installer
    network, i.e., installers that you may have been first working work
    who are not authorized SP dealers will have no choice but to argue
    for some other approach.

    I sold high tech products for almost two decades. Yes, I was in
    Sales. (I took early retirement in March, hence the "was.") What
    I learned in sales helped me be a better solar customer, so let
    me share with you how I solved the problem you describe.

    My last company wanted us to strive for long term success. To
    do that, we were famously urged to become a "trusted advisor"
    to our customers. This became my goal, and once I was able to
    achieve that status with a given customer, virtually every one
    stayed with me because of the added value I brought...and price
    became muted, to the point where the bar, so to speak, was to
    be "competitive" and not necessarily the lowest price.

    When I started to research my solar project, I wanted to find
    a company who would become my trusted advisor. In Missouri,
    we are, unfortunately, not too good at being early adopters, so
    you can count on one hand the number of companies who have
    done more than 10 installations. I did research to find the market
    leaders, and even had an off the record conversation with the
    "Green Coordinator" at my local utility to find out who they liked.

    I then contacted the company I thought could do the job best.
    I said to Dane, their President, "I want you to be my partner, not
    my supplier. I want you to educate me on the technology, and to
    give me choices. I want you to help me figure out the best way
    for me to meet my goals. In return, I will give you: a prompt
    decision to your proposal; allow you to make a fair profit;
    and I won't shop your proposal, your ideas on the street."

    Think about it: what good, decent company wouldn't accept
    this offer?

    As for the "earning trust" part, I did test our relationship: "Dane,
    I just heard that Sunpower has a higher efficiency product than the
    one you recommended, why can't we use those?" I looked for him
    to either know the answer off the top of his head, or do research
    and get back to me. Sometimes he had to do both. For the
    Sunpower question, he knew already that Sunpower didn't support
    Enphase, but he went back to Sunpower to get their product
    roadmap, which showed that there were no immenient products
    that would be compatible. I did enough research to be able to
    ask some hard questions, and I gained confidence in him when he
    responded back with well thought out answers.

    So my advice is: do your homework...pick one or at most two
    partners to work with...make them earn your trust...but you
    earn their respect by not wasting their time by going around
    "getting bids for the same thing". [If you feel you *need* to
    get additional bids, this is actually saying you don't have the
    trust yet that you need from your prospective trusted advisor.
    When you get a prescription from your doctor, how often do
    you go to another doctor to check that the first doctor's
    prescription is right?]

    Remember that you are going to have to live with the result for
    maybe 25 years, so you do your job to find the person you can
    trust to work with you to build the best solution.
     
  20. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    That requires that no company will provide single module inverters in what has to be an industry that will grow by huge factors. Hard to believe that is a real issue. (Like asking what happens if nobody builds the chargers for the electric cars of the future.) Much more likely is that in 10 years one of the panels might be compromising the whole array.