Installing 30 panels (100w, 77v) Which is the best configuration?

Hi my dad just bought 30 solar panels and I am confused as to which configuration to wire them up too, I see some installers connect them in different banks and in series or parrallel so my question is, how would you install them? Please find attached specification sheet for the ASF100 panels.

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    that would depend on the controller used. most controllers don't accommodate more than 150v with some exceptions like the midnite classic 200 and 250. that would mean without one of the higher voltage ccs that you would have to parallel all of them or damage the controller by exceeding its max input voltage.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    Depends on MPPT.

    Don't kill yourself! Panels are more dangerous than batteries when sunlight radiates on them.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    More info needed. Is this for a strict grid tie only system or battery based?
  • solarnewzealandsolarnewzealand Registered Users Posts: 13
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    Hi guys, thanks for your responses I have had experience with solar systems in the past we have 2 off grid setups in Fiji. Will most likely do the wiring at night to minimize shock hazard. This system will be grid tied so any advice you could give on how it differs from off grid would be most appreciated. I found a high voltage solar controller http://www.alibaba.com/product-gs/1000972093/40A_50A_60A_70A_12V_24V.html would this be sufficient?

    Thanks so much for your help everyone.
  • solar_davesolar_dave Solar Expert Posts: 2,384 ✭✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    Hi guys, thanks for your responses I have had experience with solar systems in the past we have 2 off grid setups in Fiji. Will most likely do the wiring at night to minimize shock hazard. This system will be grid tied so any advice you could give on how it differs from off grid would be most appreciated. I found a high voltage solar controller http://www.alibaba.com/product-gs/1000972093/40A_50A_60A_70A_12V_24V.html would this be sufficient?

    Thanks so much for your help everyone.

    That appears to be a battery charger for off grid usage. You are looking for something like one of these (these are based on USA 240V split phase 60 HZ) but there are others for differing grid setups. http://www.solar-electric.com/smasugrtiein.html BTW this is where tying them together into strings comes into play. Most grid tie inverters need a fairly high input voltage to operate properly. The Voltage levels vary among manufacturers but most are operating in the 250V to 500V ranges.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    ok to amend what i said, the controller thing applies to off grid or gt with battery backup. straight gt would be batteryless and won't need a controller.

    most gt systems will put the input pv vmp voltages above the minimum inverter voltage with enough headroom so that any higher than normal heating of the pvs will not cause the inverter to drop out due to low voltage. on the other end of things the high end inverter voc voltage limits are not usually approached as efficiencies can be lower and one does not wish to chance damaging the inverter with too much voltage. you will find these voltage requirements vary per the inverter chosen along with the pv specs that are to be applied.

    that means you will want to pick an inverter and see how it will fit with your pvs. you can run it past us if you think you have a good one selected that will work well with your pvs.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    Depends on MPPT.

    Don't kill yourself! Panels are more dangerous than batteries when sunlight radiates on them.
    That depends. The amount of current available from a solar module is limited to its Isc whereas a big lead acid battery can deliver 1000A or more.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    ggunn wrote: »
    That depends. The amount of current available from a solar module is limited to its Isc whereas a big lead acid battery can deliver 1000A or more.


    Panels are a high current tazer. I've witnessed a few electricians in my day failing to improperly disconnect a combiner box and next thing you know fingers turn into pop corn shrimp in seconds. Not to mention the long term heart palpitation conditions it causes. OSHA states anything over 7 amps of current can be deadly to the human body. Couple that with a string of panels @ 500 plus volts, and it becomes very unsightly to watch and the screams are like a man caught on fire.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    Panel current depends on insolation and resistance of the load. Whereas a GT array of several hundred Volts will provide a nasty shock, the resistance will be so high that there won't actually be any large current flow.

    On the whole ggunn is correct in that a battery bank provides a more significant danger than an array. You can't shut down the potential of a battery by covering it with cardboard, for instance.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    So to answer the original question: Since it is grid tied (strict grid tie - no batteries - correct?) - you need to know the max voltage and amp input to your inverter. Once you know that you can determine the best configuration of your array. Voltages in series are additive and amps in parallel are additive. You want an arrangement that will not exceed the voltage or amperage limits of your grid-tied inverter.
  • solarnewzealandsolarnewzealand Registered Users Posts: 13
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    After dissecting what you experts have told me I finally understand the series and parallel relationship. Have decided to choose a parallel setup and keep the voltage at 77v with a maximum current of 38.7a (1.29a x 30 panels) Had a gander at inverters on Alibaba and found some that are nearly compatible, just need to match the DC input range.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    After dissecting what you experts have told me I finally understand the series and parallel relationship. Have decided to choose a parallel setup and keep the voltage at 77v with a maximum current of 38.7a (1.29a x 30 panels) Had a gander at inverters on Alibaba and found some that are nearly compatible, just need to match the DC input range.

    I think you looked at the wrong type of inverters. Grid tie inverters typically have relatively high voltage requirements, like 200V-600V. What's more is that New Zealand will have specific regulatory requirements for inverters connected to the grid, so not all of those that are on alibaba will comply. It's more efficient and cheaper in wiring and breakers to go with high voltage series wiring in the PV panels.
    All of the big name grid tie inverter manufacturers have PV planning software available, like this: http://www.sunnydesignweb.com/sdweb/SunnyDesign/Home which will let you find the best inverter match for your panels.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    3 phase?????? Residential????? Red flags galore.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    3 phase?????? Residential????? Red flags galore.

    Well I've reread this thread 3 times and don't see anyone talking about 3-phase power until your post. Must have missed it.

    In some parts of the world 3-phase is supplied to residences, btw. And it is not a problem.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?
    Well I've reread this thread 3 times and don't see anyone talking about 3-phase power until your post. Must have missed it.

    In some parts of the world 3-phase is supplied to residences, btw. And it is not a problem.

    the link to Alibaba.com links to a 96v, 3phase inverter.

    Common supplied power sources for residential equipment is 120V/240v, most 3 phase inverters don't meet the 95% conversion/harvest efficiency threshold, so which in most cases individual string inverters are use per phase. I.E SMA, power one, unless it's a much larger string inverter in a 20kw range meant for schools or industrial application.

    also so for the purpose of safety, if the power is 208v, I would recommend a microinverter installationI.E enphase, power one, solar bridge, darphon. Then it's not a matter of engineerining parallel or series strings, or implementing DC combines which to me sound dangerous for some one to work in that doesn't have experience working with DC currents. Micro inverter efficiencies are higher and lower in price as far as cost per watt.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    What is linked to is irrelevant in this case as in fact most of the thread has been geared towards getting the OP to recognize the proper equipment for his application.

    I'm well aware of the power standards in North America and many other countries. I am also familiar with 3-phase power and how inverters can be used with it. But it is not relevant here just because there was a link to an unsuitable product.
  • solarnewzealandsolarnewzealand Registered Users Posts: 13
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    Hi, decided to go with a 231vdc configuration (10 banks of 3 x 77v) the total amperage is 12.9a. Found many inverters that serve this voltage/amperage range and I am aware of the standards as mentioned when it comes to buying Chinese made inverters (there are a couple of Xantrex models made there). I used a wire calculator attached but still am confused to what the formula is for calculating AWG size. 1.5mm2 metric sized wiring just doesn't sound right considering the panels have 100cm of 2.5mm2 as supplied by OEM. Obviously 231v 12.9a is the maximum I will be receiving on a very hot day, what will happen if there is 50 percent less photons on a cloudy day? Using the old hose pipe analysis will voltage and amps still be able to be carried efficiently at 50% less rated voltage and amperage? Attachment not found.
  • BB.BB. Super Moderators, Administrators Posts: 32,216 admin
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    How long is the wire run? 1.5mm^2 is pretty small (less than 14 awg). In our US code, we would need a bit heavier gauge wiring ~3.3 mm^2 minimum (20 amp rated, 16 amps maximum continuous for 12 AWG cable--which what is usually found on solar panels around here). (assuming a I have a good metric conversion table and our NZ friend is using mm^2 and not mm wire diameter as the units--just to be clear/accurate)

    Any way, on of the power equations is: Power=I^2 * R ... So if you have 1/2 the current (cloudy day), your losses are 1/4 as much... So, dark days are not a problem (from wire diameter/efficiency point of view).

    The length of the wire run is usually the bigger issue... You normally go up one or two wire diameters to reduce overall voltage drop and keep efficiency higher for longer cable runs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solarnewzealandsolarnewzealand Registered Users Posts: 13
    Re: Installing 30 panels (100w, 77v) Which is the best configuration?

    Thanks Bill, wiring length is 15m, I used a different calculator and came up with the same results 1.5mm2 or 16AWG. Very worried that I have based my calculations on vmax rather the voc, as the pv arrays will be open circuit at some stage during the installation, is this going to be an issue? Also I can't calculate resistance loss until the system is installed or rather I use the universally acceptable 3 -5 % wire loss, this all depends on the material used eg copper, aluminum, the length of the wire, and inverter efficiency usually around 96 percent and temperature? Are those enough factors to come to a Resistance conclusion?

    Attachment not found.
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