Why so few 12V PV panels over 100W

khotton
khotton Solar Expert Posts: 38 ✭
in General Solar Power Topics #1
I have been wanting to use the Kryocera 130TM panel, but none are available till sometime in 2008! Why is it that all the PV panel manufactures only make strange voltage "grid-tie" panels? I want to keep my system simple no MPPT with voltage set-down, but the lack of availability of basic 12V (+17V nominal) PV panels with rating greater than 85W surprises me. Is grid-tie so large of a percentage of use that it dominates the PV market?

Kevin
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
    Re: Why so few 12V PV panels over 100W

    One explanation might be that large/high-power PV modules operating at 12 V nominal mean relatively high output current. This would probably mean undesirable power loss in the array-to-controller wiring.

    Another explanation could be that many large battery-based systems operate at 24 V or 48 V nominal, so higher voltage modules work well in those applications.

    Yet another answer might be that DC-DC MPPT controller’s become cost effective for PV arrays of > ~400 W STC, and a long high voltage array may allow for smaller/cheaper wire.

    There are plenty of “large” (>100 W STC) “12 V” modules in production. In addition to the Kyocera 130, take a looks at the following:

    BP 3140
    Mitsubishi MF110EC3
    Mitsubishi MF115UE4N
    Mitsubishi MF120UE4N
    Mitsubishi MF125UE4N
    Mitsubishi MF130UE4N
    Sharp 123-U1

    Also, check data on “24V” modules very carefully. You may find that some are two “12 V” sun-panels connected in series in the J-box. These might easily be rewired in parallel to become a “12 V” module.



    HTH,
    Jim / crewzer
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  • Roderick
    Roderick Solar Expert Posts: 253 ✭✭
    #3
    Re: Why so few 12V PV panels over 100W

    Just a guess, it seems that a lot of grid-tie panels in the 160-200 watt range have 72 individual cells to achieve that power. If those cells are at the biggest economical size today, then I would expect that for a "12 volt" panel, they would use 36 cells, and end up with a panel half the size and half the power. Assuming that the cell size is already at the sweet spot of production. If that assumption is wrong, my argument falls apart.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #4
    Re: Why so few 12V PV panels over 100W
    khotton wrote: »
    Is grid-tie so large of a percentage of use that it dominates the PV market?

    Kevin

    It doesn't dominate the market, its IS the market ...
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #5
    Re: Why so few 12V PV panels over 100W

    Khotton why shy away from the obvious route and go with a MPPT charge controller. If your just setting up you PV system ?

    The reliability of a MX60 charge controller is very good about $200 more expense than a quality Xantrex or Morningstar equivilant with display fitted !

    Hardly any more complicated to install and setup

    Will give an approximate increased annual harvest of energy from your PV setp of approx 25%

    So if to keep the numbers simple lets say $5 a watt for PV panels thats $1.25
    saved on every watt purchased .
    If you purchased lets say a 400 w system 4x 100 watt panels a MPPT cc will yield approximately the same power output as a 500w PV array fitted an ordinary PWM cc.
    Its like having an extra panel. Thus 1 x 100 watt panel @ $5 x 100w equals $500 saving in your first year on PV production alone, easily making a case for MPPT .

    If you went to a 800 w PV MPPT system you would save effectively a $1000 on panels against a PWM cc designed system producing the same amount of annual power.

    Looked at another way spend the $1000 on two further panels and your getting an extra 25% power generation for each and every year for the next 20 years or so as your old out dated PWM designed setup !

    Add in the savings on lower wiring costs , ability to buy larger panels at lower cost per watt, simply by having more choice in the market place and it really is a no brainer !

    MPPT is the way, Outback set the bar, Xantrex and Morningstar are set to follow, go where the smart monies going, go MPPT.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #6
    Re: Why so few 12V PV panels over 100W

    Will give an approximate increased annual harvest of energy from your PV setp of approx 25%

    MPPT is the way, Outback set the bar, Xantrex and Morningstar are set to follow, go where the smart monies going, go MPPT.


    An energy generation increase of 25% may be possible in a year-‘round cold climate. However, I suspect that the bulk of applications see only a 10% annual increase. The combination of PV voltage drop due to ambient summer temperatures, voltage drop in the wiring, and controller inefficiency add up to very limited bulk-stage MPPT energy gain in the summer. But, a 30 C temperature swing from summer to winter can lead to a peak energy generation increase of ~15%. Additionally, in terms of just charging batteries, there’s no MPPT benefit during the absorb- or float stages due to the current limiting operation.

    I agree that MPPT is a generally good featute, but I think an annual benefit of ~10% is probably more realistic. I also agree that OutBack set the bar with the MX60. Apollo and Xantrex have announced their competitive products, and the Classic may not be too far away. The new Morningstar SunSaver MPPT is for "small" systems (~200 W – 400 W) and is not in the same league as the other “big guys”.

    HTH,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Why so few 12V PV panels over 100W

    is bluesky none existant? they've been around for quite awhile with mppt controllers though not quite as versatile as say the mx60.
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #8
    Re: Why so few 12V PV panels over 100W

    Creezer I stand corrected ! Reading too many brochures !

    but then the maths equates to the following.
    If you spend a minimum of $2000 on your array ie $5 a watt 400 watt, then at 10% performance gain means you can spend the extra $200 and upgrade from a 60 amp PWM controller to a 60 amp MPPT controller and have plenty of room for expansion, still makes MPPT a no brainer.

    I know you dont need 60 amp for 400 watt and there are smaller MPPT controllers around but I wish Id been more savvy when I started out, I have 2 C40s originally started off with 600 watts now Ive got 1600 watts installed and another 1600 to add, if you get bitten by the solar bug you always crave more !

    As PVs are very modular starting off with a MPPT controller bigger than you think youll ever need is a wise decision if you want to make a difference with your solar system. 400w seems a breakthrough which or course you mentioned earlier

    Off grid sunny spain, best days solar collection this year 302 amp hours off 1600 watt at 24 volt. Batteries bubblin nicely on 2 x Xantrex C40 PWM CC
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Why so few 12V PV panels over 100W

    that 400w isn't written in stone and even boB at one time concurred that in some instances a 200w system may suffice, but boB was more specific in saying 300w as a crossover, with that applying to the mx60 and not all mppt controllers. you be the judge. now if you have a starting point of even 100w and know you'll go higher, then by all means buy the mppt controller. i have 128w of pv into an sb50 and it does fine.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #10
    Re: Why so few 12V PV panels over 100W

    Nigtomdaw,

    I wouldn’t be too hard on myself for getting sucked into MPPT controller manufacturers’ hype of about generating more power. Judging by spec sheets from Apollo (“…up to 35% more power…”) and Blue Sky (“…Increases Charge Current Up To 30% Or More…”), such claims are not uncommon. To their credit, the Blue Sky’s SB50 user manual includes a much more realistic performance table (page 8). And, to the best of my knowledge, none of ‘em, OutBack and Xantrex included, mention that MPPT is of no benefit while charging off-grid system batteries in absorb- or float modes.

    http://www.apollo-solar.net/
    http://www.blueskyenergyinc.com/sb3048.htm
    http://www.blueskyenergyinc.com/pdf/SB50ManualF.pdf

    Don’t get me wrong: I’m a big fan of MPPT technology for off-grid systems, especially when coupled with a DC-DC stepdown feature, as well as for grid-interactive systems.

    niel,

    I honestly can’t say whether I omitted Blue Sky MPPT controllers in my earlier post by accident or on purpose. But, since you asked, let’s go there.

    The RV Power Products / Blue Sky MPPT controllers were certainly interesting when first introduced. But, their big models were quickly eclipsed by the MX60’s features, flexibility, and price. As you say, they’re not as flexible as the MX60.

    Additionally, it’s my view that the big Blue Sky controllers are overpriced. Using NAWS as a reference, the SB50DL is $512, and the 6024HDL is $539. The MX60 is $498, and the new Xantrex XW is $509.

    Considering features and price, I don’t see that I’d recommend the big Blue Sky controllers over the MX60 or the XW.

    Regards,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
    Re: Why so few 12V PV panels over 100W

    jim,
    i agree that bluesky is probably taking a big hit as their sales probably nosedived due to the mx60 being more feature packed at a lower price. it seems that the 50DL model (i have) has jumped far in price as i had originally paid about what the 50L model currently is. it was then after my purchase i became more aware of the mx60 (for about $100 more), but seeing as how i haven't expanded my pv system yet, it worked out for the best as the dl does not draw alot and i can disconnect the meter to save power if i choose to. the mx60 has gone down slightly from its original cost(probably due to high sales). but all factors weighed i've said it in the past and i'll say it now that i probably should've gone to the mx60 due to non linear downconversion ability from the mx60 (ie, odd input voltages not translated downward too low or too high if i'm correct it has that ability as in using pvs that have odd voltages like a vop of 23v to convert down to 12v) and the better temperature tracking curve options for the bts with my sunxtender's special mv/temp c needs.
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