Need advice on how to proceed

Hi everyone,
I am new to this forum and solar also and want to get advice from those who have spent time with solar. I bought a solar system from an estate that was working, but it is clear it really was never set up correctly. There were long runs of 12 ga. solid wire, bad connections, mixed controllers and so on. I want to try to set up the best system for my use. I am actually thinking more a grid tie system with a new inverter, but here is what I have.
24- Solarex SX65U panels
4- larger Solarex, I guess 100-120 watts (1 has cracked glass, but puts out 16 volts.
8 -assorted brand 65 watt panels
2- SW 4024 inverters. One was a new never used. Don’t know if he intended it as a spare or was going for 220 volt system.
3 -sun l tracking devices. Not sure brand, but uses some type gas changing from liquid to vapor to move it.
Several older panel controllers
12- good 6 volt deep cycle Trojan batteries
12 -possible 6 volt deep cycle batteries that take a charge, but cases are a little swelled.

I an guessing the SW inverter cannot be grid tied, so rather than deal with the battery expense at some point, I was thing of just going with a new inverter such as the Xantrex GT 5.0. I didn’t understand the sizing chart at all about strings and input voltage so will need so help on that and inverter sizing if that is the way to go. I live on 40 acres, so plan mounting panels close to ground for ease of maintenance. I use about 800 KW/month in winter and 1500-1800 in summer. Any advice, help and options will be greatly appreciated.
Thanks,
Jimmy

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on how to proceed

    I suggest you do this:

    1). Ignore what you've bought for starters.
    2). Calculate your load requirements.
    3). Plan a system based on that.
    4). Test all the stuff you've bought and see what works & how well.
    5). See what of your odds-n-ends fits into the design.
    6). Sell or scrap the rest.

    The reason I say this is because it sounds like much of the equipment is old, which means it's probably nearing the end of its life. Used batteries, even ones that appear good, are an unknown quantity. Solar panels lose their ability to produce over time. A cracked panel may put out 16 V, but not enough Amps to do any good. You can find a couple of recent threads here regarding the SW inverter and its current lack of support (replaced by the XW series). Solar trackers are notoriously troublesome.

    On the other hand, from the hobbyist/experimenter's POV you've struck gold. :D
    2480 Watts of panels has the potential for approximately 8 kW/hrs per day, depending on their actual performance and insolation.
    The Trojan are probably T105 @ 200+ Amp/hrs so that's 2400 Amp/hrs @ 50% = 7200 W/hrs (if they're still good).
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Need advice on how to proceed

    Regarding how to connect the panels to a large GT inverter...

    First, the panels must have UL (or other NRTL approved lap) approvals to meet code, NEC, and usually safety requirements. Second the panels should be rated to 600 Volts AC (high voltage required for Grid Tied Inverters--very old panels may not have this rating as GT was very new, or not even available back then).

    Next--the panels Vmp (Voltage, maximum power point) and Voc (Voltage open circuit) must fall in the ~200-600 VDC of the GT inverter. Vmp and Voc change based on temperature and (Vmp) on loads.

    Think of the solar panels as "imperfect" batteries that can vary over an almost 2:1 range (say worst case in high desert) in voltage--very hot days under load, the Vmp voltage may be 300 VDC; very cold days just starting up (or after a grid power failure) Voc could be near 600 VDC (depending on where you live and how cold it gets.

    So--when you put the panels together--The Vmp should match between parallel panels to within ~10%. And the series current in a string should match to ~10% for best efficiency (if the voltage or currents do not match--you waste available output energy).

    I the end, as Marc/Cariboocoot says--trying to make this all work and legal for a GT system can be almost impossibly complex (if possible) and you are still left with very old/small wattage panels, lots of wiring connections (more points of failure), etc.

    Back when those panels were purchased--they may have cost $10 per watt. Today, you can find large (around 200+ watt) panels for near $3.00 per watt (and sometimes even less) new with full 20+ year factory warranties.

    The old panels and parts... Sort through them and build an off-grid system (for DC loads or with a nice off-grid inverter)... And/or Ebay the parts you don't want. And put it to your "ideal" system (and possibly a nice Honday eu2000i genset for emergency backup (or other smallish/efficient genset for emergency backup power).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Need advice on how to proceed

    I agree that the hodge-podge of stuff is going to make grid tie tough/expensive/complicated. As Marc said, the batteries are almost no value, unless you are going to build a grid tie with minimal battery capacity. The unknown quality/age etc make them worth just a bit more than scrap.

    Wiring your collection of Pv together into a meaningful array is going to take a bunch of work with design and sizing of components. As Bill suggests, grid tie inverter volatage requirements are high enough that stringing meaningful series/parallel strings together is going to be tough.

    What you might consider is selling as much as you can to finance a "real" grid tie project. Not knowing what you paid, I would hope that you made a good deal all the way around.

    There are lot's of newbies/hobbiests who will pay a premium for single small Pv panels.

    Good luck, welcome to the forum. Keep doing your homework. There are some very smart folks here who have forgotten more about Pv than most of us have ever known.

    Tony
  • System2
    System2 Posts: 6,290 admin
    Re: Need advice on how to proceed

    Thanks for the replies. Not sure it was wanted to hear, but sounds like good advice. I could never come out on a new system (too old) so will just try to use what I have. We have an enclosed porch where we spend a lot of time, so I guess I will set the system up to heat and cool that area for as much as it will do. If using a controller such as Xantrex XW MPPT 60 Controller, do you just series say 8 of the panels to get to the 140 volts input and then series 8 more and the parallel the two together? I think I would just use the 12 newer Trojan batteries and 24 of the 65 watt panels that are all the same. I could then sell the other inverter (one on eBay now at 1200.00) to pay for the controllers. What kind of amp draw could I probably draw with this system continuous for 24 hrs a day in the real world? I live in the center of Texas.

    THX
    Jimmy
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Need advice on how to proceed

    I did not find the Solarex 65watt panels on the Xantrex sizing tool for the XW Charge Controller...

    In any case the Vmax of the controller is 140 VDC (operating) and 150 VDC non-operating... So--you don't want to have your panel Vmp voltage anywhere near that high.

    Basically, the minimum Vmp of the panels should be the maximum charging voltage of your battery bank plus 1-2 volts...

    The Maximum Vmp/Voc should be less than 140 VDC.

    For a ~17.1 volt Vmp panel... You can run as few as 1 panel string for a 12 volt battery bank. And as many as 5-6 panel series string for a 48 volt battery bank.

    Note, you can put many strings in parallel to boost the array's total current (and power into the charge controller)--But, the controller will (safely and by design) limit its output current to a maximum of 60 amps--no matter how many solar panels you put in front of the controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on how to proceed

    so you don't feel you lost out on an opportunity, you can still run a dedicated off grid (closed circuit) to run certain things. although it's old i would still use the stuff you determine to still be good and that determination is the hard part. as an example you may have a freezer that could be run or an air conditioner or even a bunch of lights or any combo of these depending on their daily wh draw and what you can produce per day with that old stuff.
    in the meantime you can save for and research the gt system you'd want.
  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Need advice on how to proceed

    the SW was grid tie capable. I say use what you got and have fun with it
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Need advice on how to proceed

    If I recall correctly--only certain models/options of SW were GT capable... And I doubt that any of them would come close to meeting current UL/NEC requirements for a "new install" (if anyone were to find the correct hardware and bother looking up the old certificates).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on how to proceed

    i made mention of a dedicated off grid type thing so that the scrutinizing from nec regulations won't be as bad as it won't be connected to the grid in this way. i did forget to say it is gt capable, but then the other non approved items will come into play and a heavier hand dealt by nec regs.

    edit to add;
    then again it is an already established system and not a new system looking to be installed so it may not be required to get all the new and up to date stuff for it.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on how to proceed
    niel wrote: »
    i made mention of a dedicated off grid type thing so that the scrutinizing from nec regulations won't be as bad as it won't be connected to the grid in this way. i did forget to say it is gt capable, but then the other non approved items will come into play and a heavier hand dealt by nec regs.

    edit to add;
    then again it is an already established system and not a new system looking to be installed so it may not be required to get all the new and up to date stuff for it.

    I don't think it counts as an established system if it's taken down from one site and reconstructed at another.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on how to proceed

    ok i missed that tidbit of info, but for the rest you get my point i hope.
  • System2
    System2 Posts: 6,290 admin
    Re: Need advice on how to proceed

    Thanks guys,
    I think I will wire up some of the stuff I have and see how it does. I will use the tracking arrays with 8 65 watt panels on each array. Even if they don’t track well, it will get them up where the cows won’t harm them and I guess I could just fix them at the correct angle. I am not sure about the wire size at all. The inverter is 24 volt input so would I series two panels together and run that to the solar controller and then do that 4 times, maybe with 10 ga. stranded wire or is it better to parallel four sets together at the array and then run only two large wires to the controller? The distance to the controller and batteries will be ~100’. Then would I use three 60 amp. solar controllers and parallel those connections at the batteries? Again thanks for the help.

    Jimmy
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Need advice on how to proceed

    see the voltage drop calculator in this link,
    http://forum.solar-electric.com/showthread.php?t=29
    note that that is a long distance to run the wires and larger wires should be used to overcome the voltage drops from the higher resistances that distance will impose. whether you run separate wires back or not the voltage drops have to be accounted for.
    if you exceed the capacity of a controller then yes put more inline to handle the power. do not make the pvs common to all controllers as any pv should only go to one of the controllers. the only common point for the system will be at the battery(s). somehow i feel this is confusing, but understand that you will parallel only the numbers of pvs to meet your controller's needs and any other controller shall have their pvs going separately to their own controllers.
    with a long run the use of higher voltages will become advantageous, but that necessitates using an mppt controller that can downconvert. keep in mind that when downconverting with an mppt controller that the current increases along the same ratio the voltage is reduced and will have some gain also due to mppt.