Comparing Sharp 208's with Sharp 170's

dale
dale Solar Expert Posts: 29 ✭
in Grid Tie and Grid Interactive Systems #1
All,
I'll be putting my system up within a month. Initially, the system was to have a Xantrex GT 3.0 and eighteen Sharp 170's.

Space is limited on my house, so I'm considering using fourteen (or maybe sixteen) 208's which will take less space and leave room for expansion. Using a Xantrex GT3.8 or GT 4.0 would allow room to expand later.

My questions are whether the 208's perform better than the 170's and if I'd be able to mix (rated) panels at a later.

Thanks,
Dale
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Comparing Sharp 208's with Sharp 170's
    dale wrote: »

    My questions are whether the 208's perform better than the 170's and if I'd be able to mix (rated) panels at a later.

    Thanks,
    Dale

    170 & 208 are not rated the same, and you should not mix them.

    If you have the panel dimensions, you can divide watts / square inches (or cm) and figure if their power densitys are different.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #3
    Re: Comparing Sharp 208's with Sharp 170's

    so I'm considering using fourteen (or maybe sixteen) 208's which will take less space and leave room for expansion. Using a Xantrex GT3.8 or GT 4.0 would allow room to expand later.

    Dale,

    The system you’re won’t work particularly well, if at all. Here are some limiting factors:

    1) Fourteen 208’s wired in a single series string will approach the inverter's max Vdc
    2) The voltage from the 14 modules wired 7 (in series) x 2 (parallel strings) won’t be high enough to operate the inverter
    3) The inverter can’t handle sixteen 208’s wired in series
    4) The voltage from the 16 modules wired 8 (in series) x 2 (parallel strings) is considered to be a “non-optimal” configuration by Xantrex.
    5) Your location's environmental conditions (unknown by us at this time) may affect the statements above

    An starter combination of 208’s and the GT 3.8 might be 18 modules wired 9 X 2. I urge you to use Xantrex’ GT inverter sizing tool to model your system. See: http://www.xantrex.com/support/gtsizing/index.asp

    It is possible to “mix and match” PV modules and strings. Modules wired in series should have the same Imp spec. Modules or strings wired in parallel should have the same Vmp spec. Array voltages for utility-interactive inverters like the GT can get pretty high (200 VDC to 550 VDC), and local temperature can greatly influence these values, so module temerature coefficient and/or NEC Table 690-7 must be taken into consideration.

    HTH,
    Jim / crewzer
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  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    #4
    Re: Comparing Sharp 208's with Sharp 170's

    Dale, Crewzer's got the correct approach on how to define what you should do.

    My input would be size up now and get to an optimal point with your array and inverter. If you do 'oversize' the system, you'll have the luxury of cooking, having lavish parties, etc knowing you're paying for the electricity with the sys.... Also, if your state does eventually pay you for excess energy, then you'll get payback sooner as elec rates continue to increase....
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