Solar Panel Selection

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hi,

Seeking some help on solar panel selection basics - links / recommendations etc... I am in the process of buying the components for a house that is completely off grid. Framing was just completed but I am shut down for the winter. I have started purchasing components as I get the funds (because if I don't the money has a habit of disappearing). Scalability and ease of installation are most important. I have purchased my inverter VFX3648, MPPT MX60, and 8 104amp/hr batteries (enough to get started). Looking to spend 6k -7k for 8 panels in the 150-180 watt range. Battery system voltage - 48v

Location specifics - central UT, elevation - 6300 ft, max summer temp - 95deg Max snow 2-3ft.

Thanks!

Kent
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
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    Re: Solar Panel Selection

    Kent,

    Your PV array specs for your “48 V” system will be narrowly bracketed at the low end by a minimum operating voltage requirement and hot temperature, and at the high end by equipment input voltage limits and cold temperatures.

    The combination of high ambient temperature and losses in the array wiring and the charge controller could result in a voltage level of about 75% of array STC Vmp spec being delivered to the battery bank. If you need 62 V to charge and EQ the 48 V bank, the array’s STC Vmp spec should be ~62 V / 75% = ~83 V.

    Low ambient temperature early on a winter morning in your neck of the woods (-5F to -40 F range?) could cause the array’s Voc to increase by ~25%. The MX60’s operational limit is ~140 VDC, so you’ll likely need to build an array rated at 140 Voc /125% = 112 Voc STC.

    The challenge now is to build an array for between $6K and $7K, rated at between 1,200 W STC and 1,440 W STC, and with array voltages of >/= 83 Vmp </= 112 Voc.

    One option is an array of ten Kyocera KC-130’s wired in a 5 (in series) x 2 (in parallel) array and rated at 1,300 W STC. With STC module specs of 17.6 Vmp and 21.9 Voc, the array’s STC voltages would be 17.6 Vmp/module x 5 modules = 88 Vmp, and 21.9 Voc/module x 5 modules = 109.5 Voc.

    At $2,390/four modules, ten should cost ~$6K (plus shipping). This configuration meets your goals for price and power, and it meets the electrical spec limits described above. A 1,300 W array should also be a comfortable match for your 48 V x 210 Ah battery bank. Perfect!

    I skipped the associated current calculations, because, as you probably know, the MX60 can easily handle a 1,200 W STC – 1,440 W STC PV array when operating in a 48 V system. In terms of scalability, the controller could comfortable handle at least 20 of these modules (2,600 W STC) in five-module increments, and perhaps even 25 (3,250 W STC), should you decide to expand your system at a later date.

    HTH,
    Jim / crewzer
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #3
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    Re: Solar Panel Selection

    For your off grid, you can't beat this deal

    www.sunelec.com, check out the Sun modules ( Evergreen seconds ) for 3.15 watt. I have a system I put up in June with 30 of them, GREAT performing panels ... best tolerance in the industry with +4%/-2%
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  • System2
    System2 Posts: 6,290 admin
    #4
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    Re: Solar Panel Selection

    Just a thought, perhaps I misunderstand, but if you already have your batteries, how do you intend on keeping them "toped up" until you get your system completed?
    Wayne
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  • System2
    System2 Posts: 6,290 admin
    #5
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    Re: Solar Panel Selection

    Thanks for showing me the rational on panel selection Jim.

    In regards to the batteries.... Construction schedule slid about 2 months hence I was not able to integrate them into my power system (currently a generator). I currently have them stored at room temp and am going to follow the manufacturers recommendation - http://www.sunxtender.com/xtenderservice.php

    Thanks,

    Kent
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  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #6
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    Re: Solar Panel Selection

    As solar guppy suggested, I also bought some of the sunelec panels and they perform right up to spec at a very reasonable price. I bought 6-190 watt panels in July and was lucky to get them @ $2.74 a watt. I'm very happy with them.
    Larry
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #7
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    Re: Solar Panel Selection

    Kent,

    Solar Guppy and Larry’s suggestions are definitely worth considering. Although the Evergreens could (would?) be problematic if used with flooded-cell batteries in your environment, they should work very nicely with your 48 V system based on Concorde SunXtender AGM batteries.

    AGM batteries typically require a lower absorption voltage (~14.3 V for a 12 V battery) than do flooded-cell deep-cycle batteries (~14.8 V for a 12 V battery). Additionally, AGM batteries generally aren’t equalized, so they don’t need the ~15.5 V EQ charge voltage (~62 V in a 48 V system) required by flooded-cell batteries.

    Accordingly, you should be able to get by with a lower array voltage than I described in my previous post. Using Concorde’s max spec of 14.4 V for a 12 V battery means that the 77 F charge voltage for your 48 V battery bank will need to be 14.4 V x 4 = 57.6 V at most. As long as your PV array’s STC Vmp spec is 57.6 V / 75% = ~77 V or better, you should be OK, subject, of course, the Voc limit discussed previously.

    Wiring four of any of the Evergreen modules in series in your environment will result in a temperature-corrected winter Voc of >150 V. This exceeds the absolute maximum input spec of your MX60 controller, as well as that for the Xantrex and Apollo controllers.

    But, three modules wired in series should work just fine. For example, the winter Voc of three 180’s wired in series could be 32.6 V x 3 x 125% = ~122.25 V – no problem. The STC Vmp spec would be 25.9 V x 3 = 77.7 V. This could drop to 77.7 V x 75% = 58.3 V (net) in the in your environment’s summer, but that would still be just high enough for your particular batteries.

    So, series strings of three Evergreen Spruce 180’s or 190’s should work for you. Nine 180’s in a 3 x 3 array would be rated at 1,620 W STC. At $3.14/W, they would be ~$5,100, plus shipping.

    HTH,
    Jim / crewzer
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  • System2
    System2 Posts: 6,290 admin
    #8
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    Re: Solar Panel Selection

    Sir,

    i want to buy solar panels for a 5kW system.. what kind of panels that i can go for? what are the desired features that determines performance?

    please mention the required characteristics for a good panel??
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #9
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    Re: Solar Panel Selection

    For standard solar PV installations, there are three major types of solar panels.
    • Mono-Crystalline: Most expensive and slightly more efficient (watt*hours collected). If you have a limitation for roof space--will give you the most power. Panels are usually warranted for 20-25+ years to 80% of new power value. Panels, if not broken by rocks/hail/etc. and are a well made brand--should last upwards of 25-40 years.
    • Poly-Crystalline: Slightly less efficient than Mono-Crystalline panels. Otherwise virtually identical materials, warranty and overall performance.
    • Thin Film: There are several major types of thin film. In general, they are 1/2 the price of M/P crystalline panels and 1/2 as efficient. You will need ~2x the roof space and rack space to collect the same amount of power. You may find some panels with 10 year warranties, and they do not seem to last as long as crystalline panels. Also, there is a ~6 month burn-in period with many thin film panels. When first installed, you may get >20% more than rated power--but they will burn in and stabilize at their rated power over a ~6 month period. There have been major issues with the long term reliability of thin film panels. Try to stay with good vendors and glass cover sheets. Flexible (plastic panels) don't seem to last as long either.
    Many panels (especially thin film) are advertised as being better in hot weather/cloudy weather/etc. than crystalline panels... In real life, the overall performance of all types of panels are very similar (most are based on silicon as a base material--and whether crystalline or thin film--the physics is the same). All panels need to be installed in full sun, and output current is based on the amount of Watts per square Meter of sun hitting the panel. Less sun (cloudy weather, panels not facing sun) will reduce output of panels. Any shade can dramatically reduce the output of panels (do not allow branches, overhead wires, near by poles/vent pipes, etc. cast any shadows on the arrays between, at least, 9am and 3pm).

    All panels have their Vmp (voltage maximum power point) fall as the panels get hotter--Mounting panels 5-6" or higher off of a roof or on free standing mounts will help keep them cooler and produce more power for you.

    And even well known vendors can have their panels fail after 5 years--So look for vendors that will be around for awhile and have a good history (helps, but is not a guarantee that there will not be any problems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #10
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    Re: Solar Panel Selection

    I just went back to Solarguppies comment to this thread from back in 2007. He referred to www.sunelec.com. I checked out this site with excitement on solar panel prices. Evergreen 215 watt panels for $440 each. Suntech 275 watt panels for less than $400 ea.

    I'm about to add at least another 2500 watts to my insufficient system and had been looking at 225 watt Kyocera panels for $580 each.

    What am I missing here? Both suppliers are here in Arizona...
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #11
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    Re: Solar Panel Selection
    What am I missing here? Both suppliers are here in Arizona.
    ..
    One supplier is selling grade A panels and the other is selling seconds. Should be same Evergreen warranty on both.
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  • arkieoscar
    arkieoscar Solar Expert Posts: 101 ✭✭
    #12
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    Re: Solar Panel Selection

    Kyocera panels have a great reputation for warranty issues and are normally more expensive than Sun or Evergreen. When I had a couple of Kyocera panels fail 11 yrs. ago, they replaced the whole array and paid shipping both ways when they realized the problem was their fault.
    I will pay a premium for quality although I have used both Sun and Evergreen without problems.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
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    Re: Solar Panel Selection

    "Kyocera panels have a great reputation for warranty issues"

    that might read better if it stated, Kyocera panels have a great (meaning good) reputation for handling warranty issues. it might be misconstrued in a different meaning otherwise so i thought i'd clarify it a bit hoping this is how it was meant.
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #14
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    Re: Solar Panel Selection

    I've used the Kyocera panels in my previous system with great success, but I'm looking at saving several thousand dollars with both the Evergreen & the Sun panels. 'm not a wealthy person just trying to go Green......
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #15
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    Re: Solar Panel Selection
    Evergreen & the Sun panels.
    My understanding is that the Evergreen seconds are factory warranted while those labeled as SUNS are not factory warrantied. I wouldn't bet on which company lasts another 25 years in business, though in today's business climate, with the big car companies going under I would wonder about the rest also.
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #16
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    Re: Solar Panel Selection

    It can be a little similar to a trip to Las Vegas and a craps table.

    I will definitely get the information right on the warranties, although most of the appeared to be "A" panels I will be going down to Phoenix on Friday and will be talking with them.....
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