how do I get a single sunpower panel???

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Skyko
Skyko Solar Expert Posts: 121 ✭✭✭✭✭
in General Solar Power Topics #1
I would like to put a 30 to 40V panel on my sailboat (I need that voltage, and it is more efficient not to have to boost it from 15V). About the maximum size I can fit is something like the Suntech STP175S, which does have a Vmp of 35.2 volts, but I also saw that the SunPower 230 watt panels with a similar (maybe slightly higher Vmp) are actually smaller in size! 55 more watts for a smaller panel, but I can't find anyone who sells a single panel and the company refered me to an installer in my area (who seems to be on a month vacation). Is there any way to get a single quantity of one of these or is there another manufacturer with a 18.5%+ panel efficiency like sunpower?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    Re: how do I get a single sunpower panel???

    I sent you a personal message as to where you might find Some that would work.

    SunPower typically sells only through installers, so they are not marketed like other panels. They are also Positively grounded. Not sure you'll need to worry about this on a boat?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #3
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    Re: how do I get a single sunpower panel???
    Photowhit wrote: »
    I sent you a personal message as to where you might find Some that would work.

    SunPower typically sells only through installers, so they are not marketed like other panels. They are also Positively grounded.
    What do you mean by that? Neither of the current carrying conductors are grounded (connected to the frame) on any solar module that I know of; if that weren't true you couldn't put them in strings.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #4
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    Re: how do I get a single sunpower panel???

    The Sun Power Positive Ground issue has a long and interesting history--and one that appears to have disappeared from the web.

    Short summary--Because of the way the high efficiency panel is designed--If you run the panel with a "floating ground" or "negative ground system" (most off-grid systems end up with negative grounded panels, and most GT systems because of NEC ground fault detection requirements require grounding of the DC solar panel bus--and the default is to negative ground--although many vendors now offer positive grounding options for their GT inverters because of Sun Power).

    What happens is a negative grounded multi-series panel string builds up excess electrical charges in the solar cell itself. This causes somewhere between 10-40% or so depression in output power of the array.

    By reconnecting the array to a positive ground, the excess charges in the cells were dissipated within a few hours (or faster?).

    Here is one thread, with links to others with more discussions about positive grounding the Sun Power panels:

    Sunpower positively grounded modules

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #5
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    Re: how do I get a single sunpower panel???

    Thanks Bill, a much more complete answer than he would have gotten from me...lol.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Braden
    Braden Registered Users Posts: 9 ✭
    #6
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    Re: how do I get a single sunpower panel???

    the only other manufacturer I can think of that has efficiencies close to SunPower are the Sanyo HIT models.
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