Adding New PV Panels to my existing system....

creosote
creosote Registered Users Posts: 16 ✭✭
Greetings folks. This is my first post on this forum and I have been very impressed with all the very helpful people on here that explain
stuff for those of us who are still learning.

I bought a home in FL that already has a Hybrid system consisting of 12 Evergreen 195 panels (~2400w) and a Whisper500 3Kw wind turbine. Both
feed back to a Xantrex 6048 Inverter w/ a XW MPPT60 Solar Charger controller and a separate Charge controller for the turbine. Also have a 1000
Amp hour battery bank (16 Deka 8d's). The system is grid tied also and sells back to our power company any excess electricity.

I have another 12-14 PV panels of SunPerfect Momo 255w (Voc: 60.1 Vmp: 49.5 Isc: 5.56 Imp: 5.15 TempCoef Voc: -.35 Temp Coef Vmp: -.474)
that I want to add to my system. The current cable run from the PV panels/combiner box to the Charger controller is ~110 ft. using AWG 6 wire.

I plan on getting another Charge controller and trying to figure out if the XW MPPT60(150v) will do or should I step up to the MPPT80(600v) since it
can handle 600v vs only 150v on the other. I'm also trying to minimize the wire size for the run since it will likely be around 125ft. With the MPPT60
it look like I can only run these panels in a 2 per series setup since they are such high voltage (60.1 x 2= 120.2v + temp adjustments) and therefore
have to run 6 or 7 strings into a combiner box. But the problem there (I believe) is the current of all those strings (6 x 5.56a = 33.36amps) would be
very high and I'd need very large wire to run back 125ft. I'm not sure if I'm calculating this correctly to please let me know if I'm off.

But, if I go with the XW MPPT80 I can put 6+ panels in series on a string and have just two strings while easily staying in the proper Min/Max voltage
ranges. Then I would only have 2 string of 5.56amps = ~11amps total current having to run back the 125 ft and can use much smaller wire.

So that's my issue, as well as any other factors I may have left out. I'm pretty sure my XW 6048 can handle the additional ~3000 watts from this
new PV array. The Wind turbine is pathetic here in FL and barely produces anything unless we have consistent 15-20mph gusts..so barely factors into
the over all power input. The current solar array rarely every produces more than 2100w peak and is usually less. I'm getting about 9-10Kwh total
on good days.

Are there any other pitfalls or issues I'm not considering? Any limitations that may cause problems with this setup?


thank you...

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Adding New PV Panels to my existing system....

    Welcome to the forum.

    Let's do some math! :D

    You've got a 2400 Watt array plus a 3kW turbine (5.4 kW total) feeding a 6 kW inverter.
    Now you want to add twelve to fourteen 255 Watt panels (3060 to 3570 Watts total).
    I make that 8970 Watts. Derated it would probably perform at about 80% of that, or 7176 Watts.
    Pushed through a 6kW inverter = 6kW.

    Now arguably the turbine probably doesn't produce 3kW all the time. Possibly not ever. And no doubt the panels will not be at their maximum potential all day long either. Technically your max is about 20% over the inverter's rating, so from that POV it should work.

    I think your batteries are 370 Amp hours, so the bank is 740 and that meets Xantrex's recommended minimum for handling AC ripple. We're still good.

    So let's look at panel compatibility. Chances of the Evergreen's being compatible with the SunPerfect on the same array: about nil. Very little chance of the Vmp or Imp being close enough to mix them together.

    As such getting a new controller for the new array would be your best bet. Getting another Xantrex MPPT60 is the logical choice as it can 'talk' to your other Xantrex equipment and should be able to handle even the fourteen new panels (output around 57 Amps).

    I'm not surprised at the wind turbine's poor performance. You might want to take that down entirely, as it would increase safety during hurricanes. Or if you really want to invest in it, go for a Windy Boy from SMA and dedicate the turbine's output to grid. But that's probably throwing good money after bad.
  • creosote
    creosote Registered Users Posts: 16 ✭✭
    Re: Adding New PV Panels to my existing system....

    Thanks for the fast reply! You're correct.. at first glance it appears I am putting too much power through my inverter, but the wind turbine almost never
    produces enough to be a factor (except when it's cloudy/stormy and very windy...hence the PV's aren't making any power). So I too was thinking about removing it from my setup.. Hey..Anybody want to buy a 3 yr old Whisper500? Poles, guy wires, controller and ALL.. ;)

    One thing I was hoping you'd comment on is my math for the PV string amperage. I think I may have calculated that incorrectly. I was adding
    the Volts and Amps for each string together since I would need 6 strings with the MPPT60. Each string consisted of 2 panels (60.1v & 5.56a per panel)
    so a string would have 120.2v (adding the voltage together) and only 5.56 amps (not adding amps together)..correct? SOOO... When you combine
    these 6 strings together you add the Voltages (120.1v x 6 = 720.6v) BUT.. I don't think you add the Amps together (that's what I was doing before)..so
    my total amperage would remain only 5.56am for all 6 strings put in a combiner box and run 125 ft back to my Charge controller/inverter.

    That would be great..because I could use much smaller wire if all I have is 5.56a vs 33a+. Please verify if I am calculating this correctly.




    Welcome to the forum.

    Let's do some math! :D

    You've got a 2400 Watt array plus a 3kW turbine (5.4 kW total) feeding a 6 kW inverter.
    Now you want to add twelve to fourteen 255 Watt panels (3060 to 3570 Watts total).
    I make that 8970 Watts. Derated it would probably perform at about 80% of that, or 7176 Watts.
    Pushed through a 6kW inverter = 6kW.

    Now arguably the turbine probably doesn't produce 3kW all the time. Possibly not ever. And no doubt the panels will not be at their maximum potential all day long either. Technically your max is about 20% over the inverter's rating, so from that POV it should work.

    I think your batteries are 370 Amp hours, so the bank is 740 and that meets Xantrex's recommended minimum for handling AC ripple. We're still good.

    So let's look at panel compatibility. Chances of the Evergreen's being compatible with the SunPerfect on the same array: about nil. Very little chance of the Vmp or Imp being close enough to mix them together.

    As such getting a new controller for the new array would be your best bet. Getting another Xantrex MPPT60 is the logical choice as it can 'talk' to your other Xantrex equipment and should be able to handle even the fourteen new panels (output around 57 Amps).

    I'm not surprised at the wind turbine's poor performance. You might want to take that down entirely, as it would increase safety during hurricanes. Or if you really want to invest in it, go for a Windy Boy from SMA and dedicate the turbine's output to grid. But that's probably throwing good money after bad.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Adding New PV Panels to my existing system....

    Series connections: Voltage goes up, current stays the same.
    Parallel connection: Voltage stays the same, current goes up.

    So when you put two 60.1 Vmp 5.56 Imp panels in series you get a string with Vmp 120.2 Imp 5.56.
    When you put six of these strings in parallel you get an array of 120.2 Vmp and 33.36 Imp.

    That's what you'll be running through the 125' of wire to the charge controller. You're looking at 6 AWG wire to make that run with <3% V-drop. But with that much Voltage available perhaps losing a bit of power there is worth saving on the wire? 8 AWG would be about 4.5% drop.
  • creosote
    creosote Registered Users Posts: 16 ✭✭
    Re: Adding New PV Panels to my existing system....

    Ok.. That finally explains it. It's putting the multiple Strings in Parallel where you have to add your Amps together to get the total load.

    I'm considering the XW MPPT80 600V charge controller which would allow me to run 6 panels per string and have only 2 strings total for
    an array of 360.6 Vmp and a whopping 11.12 Imp!! I could then run 12 or 14 AWG wire the full 125 ft. and be well within the allowed
    <3% drop.

    thanks!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Adding New PV Panels to my existing system....

    There is a downside to running very high Voltage arrays: the greater the difference between system Voltage and array Voltage the lower the efficiency of the charge controller.

    Also be aware that the 600 Volt Xantrex controller is very expensive: http://www.solar-electric.com/xaxwmp80amp6.html $1,200 vs. $480 for the standard 150 Volt version.