Grid-Tie choice ?

NEOH
NEOH Solar Expert Posts: 74 ✭✭
How do I go about selecting the proper/compatible Grid-Tie device for my specific Solar Panels (8 x 205W Evergreen) ?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Grid-Tie choice ?

    Roughly, you are looking at a GT inverter of 1,400 watts or a bit larger...

    1,500 watt GT central inverters seem to be a bit more expensive ($$$/watt) than the 3kW or larger... Are you planning on adding more panels later?

    The Enphase modules may be more cost effective for a small solar array--But you to purchase their monitoring system to see that everything is working (plus internet and web hosting charges if you want their online monitoring package--so that adds costs too).

    And first, you need to figure out if your utility supports Grid Tied / Net Metering (a decent 1 year net metering program vs just paying you wholesale cost of power).

    And check with your local building department--quite a few out here use building permits as a revenue source--so a small install may have significant permitting fees too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jcgee88
    jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Grid-Tie choice ?
    BB. wrote: »
    The Enphase modules may be more cost effective for a small solar array--But you to purchase their monitoring system to see that everything is working (plus internet and web hosting charges if you want their online monitoring package--so that adds costs too).

    FYI, the Enphase subscription fee valid for five years is $45.
    You can then access realtime stats from any web browser
    capable device, e.g., PC and smart phone.

    You still have to have high speed Internet access, of course.
    (but who doesn't these days? :)

    John
  • NEOH
    NEOH Solar Expert Posts: 74 ✭✭
    Re: Grid-Tie choice ?

    "... The Ohio Supreme Court's unanimous decision on June 5, 2010 means that net metering still provides a FULL kilowatt hour rate credit for electricity sent back to the electric grid during a billing period, up to the point where the customer-generator has offset his own usage. If, at the end of the period, the customer-generator has sent more power back to the grid that he has used, the excess power will now be credited at the rate equivalent to First Energy's generation cost.
    This means that the full retail rate is not credited by net metering for Excess power into the grid since the average generation rate is only about 3.3¢/kilowatt hour of the 12¢/kilowatt hour retail rate for First Energy (numbers are smaller, but in similar proportion for other Ohio investor-owned utilities). ..."

    I would need a 12 KW Solar Panel System to break-even given my usage. I do not expect to exceed my usage in any month with 1.64 KW.

    Yes, eventually I would like to add more Panels. When I do not know.

    No Zoning - I do not live within any city limits. I don't even have any Township Zoning Regulations. I only have to abide by National Electric Code, State of Ohio and Federal laws.

    I do not have High Speed Internet at this time for Enphase.

    I have sent a message to First Energy's Net Metering Department to see what paper work they require from me.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Grid-Tie choice ?

    A 12 Kw system is quite large actually, but who am I to talk with a 12.5Kw system. But in my defense, I have very large AC loads. First just remember conservation is your friend here, look at your loads first.

    One way to proceed is to head for a pair of grid tie inverters, and populate the first one to at least 50%-60% capacity. You can then incremental add to your system as needed or as funds become available. Once the first inverter is full add the second one. Use Panels that will be available for the foreseeable future so the adds per string are easy. While you can mix and match panels, they need to be spec'd to within 10% of the originals. The Inverters work best when loaded higher but most still hit pretty good efficiency even if not loaded up. This kind of plan is sort of a 4 step process to get your max needs.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Grid-Tie choice ?

    What is the period? If 1 year net metering--Usually a really good deal for the consumer (if the meter/billing charges are reasonable--mine are ~$6 per month and include a bit of power--Others here have been hit with $25+ per month net metering charges--second meter and cost to install, etc.)...

    A couple of things to consider--South facing roof with little to no shade 9am-3pm at least (winter/summer). Also, what is your electric service/breaker-fuse box capacity... If you have less than 100 amp box--you probably will need to upgrade (my 125 amp service will support ~3 kW array).

    There can be a lot of hidden costs with adding GT solar (especially if you do it 1.5 kW at a time--permit fees, electrician charges, electrical upgrades, re-roof for 25+ year life so you don't have to R&R panels, some localities charge property taxes on solar RE equipment, etc.)...

    I know we have been down this discussion before (I did not look up your original thread)--But if there is any conservation you can do first with your limited funds--that is usually a much better investment than solar GT at $0.12 per kWH (in California, heavy power users can pay $0.40 to $0.60+ per kWHr--At some point, the rest of the country may catch up with the left and right coasts--but not so far...).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NEOH
    NEOH Solar Expert Posts: 74 ✭✭
    Re: Grid-Tie choice ?

    My original post was under Wind. That is on-hold for now. I have done all conservation, really. I had cleared a couple acres for a Wind Turbine but I cannot cost justify that (just yet?). But, I got these 8 x 205W Evergreen panels for just $2,000. I plan to mount them "near the ground" on the south side of my property - with no obstructions from east horizon to west horizon. OK, maybe there is this one tree 1/2 mile to the East but think it will be is OK. My friend (who likes to weld stuff) and I will make a one or two axis tracker this summer. That should significantly boost my solar harvest from 4 Hours / Day to almost 6 hours / day? I have a friend who is an electrican, he said, he would connect everything for free if I paid for all wire and supplies.

    The price, so far, is right.

    So the "checklist for proper GTI selection" is ...
    1) Max PV Voltage in winter must be below GTI MAX Input Voltage
    2) Min PV Voltage in summer must be above GTI Min startup vaoltage
    3) GTI Wattage = approx 85% of PV Watt (1,400W GTI = 85% x 1640W PV)

    Should I also consider the Voltage Range for MPPT on the GTI?
    Anything else ?

    This just the beginning for me.
    I want to be off-grid within 5 years (Solar + Wind + Solar Heat).
    I was thinking of putting the Solar Heat on the South Roof.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Grid-Tie choice ?

    Distance from Array to GT inverter (vs GT inverter to electric meter)...

    I am a big fan of running the long distance wires a Array DC output... Generally it is higher (300-400 VDC) vs the 240 VAC (lower current required) plus there is the "voltage rise" possible with a large GT system (some places have high line voltage in the ~250-255 VAC--Inverters will shut down at ~260-264 VAC--so long AC branch circuit runs can have 5+ volt rise+surges--and end up kicking inverter into 5 minute time out--One of the drawbacks with Enphase / micro inverters).

    Also, look at the operating voltage of the GT inverter DC input... Some run from ~200 to 550/600 VDC--Others are closer to ~250-400 VDC... If you live in a region with temperature extremes, 250-400 VDC range is pretty tight--Also this limits your Array sizing to a few series/parallel configurations--If you already have X number of panels, it may be difficult to get all of them in a "valid" array configuration.

    Another thought--I am a big believer in pure GT inverters--But if your heart is set on going off-grid / emergency power for long periods of time (ice storms knocking out power, etc.)... You may wish to look at going with a Hybrid Inverter system (like the Schneider/Xantrex XW system).

    It can do your Grid Tied today, it can do emergency off grid (with generator backup) today, and it can run off grid tomorrow without any major changes (perhaps adjusting your emergency / back genset choices).

    Plus, if you do the Hybrid today--You probably qualify for more tax rebates/various green credits now vs in the future (government going broke/off-grid systems are not qualified for nearly as many cash/credit back programs).

    And--with a hybrid system...You can build out your inverter/battery bank with your first round of cash--and you have a nice whole house UPS system... And add solar panels+charge controllers later, as your funding permits (perhaps add the first set of panels to qualify for some of the solar rebates/credits).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NEOH
    NEOH Solar Expert Posts: 74 ✭✭
    Re: Grid-Tie choice ?

    Xantrex GT 2.8, MPPT Range is 195V to 550V
    8 Solar Panels x 18.2 Vmp = 145 Volts (too low?)
    I think I need a few more Panels for proper Xantrex GT 2.8 MPPT operation?
    12 Panels x 18.2 Vmp = 218 Vmp
    12 Panels x 22.7 Voc = 272 Voc
    using 0.31%/C
    COLD, 0 Degrees C, 272v + (272v x 0.31%/C x 25C) = 293 Voc (not too high?)
    HOT, 40 Degres C , 218v - (218v x 0.31%/C x 15C) = 208 Vmp (not too low?)
    Look good ?

    Will the Xantrex GT 2.8 run efficiently with 12 panels at 2,460 Watts ?

    Evergreen 205W specs ...
    114 Cells
    Power (Watts) 205
    Maximum Power, Pp,max = 210 W
    Minimum Power, Pp,min = 205 W
    Voltage, Vmp = 18.2 V
    Current, Imp = 11.27 A
    Open Circuit Voltage, Voc (Volts) = 22.7 V
    Short Circuit Current, Isc (Amps) = 11.93 A

    Temperature Coefficients
    αPmp: -0.43 %/°C
    αVmp: -0.40 %/°C
    αImp: -0.03 %/°C
    αVoc: -0.31 %/°C
    αIoc: +0.05 %/°C
  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Grid-Tie choice ?
    NEOH wrote: »
    Xantrex GT 2.8, MPPT Range is 195V to 550V
    8 Solar Panels x 18.2 Vmp = 145 Volts (too low?)
    I think I need a few more Panels for proper Xantrex GT 2.8 MPPT operation?
    12 Panels x 18.2 Vmp = 218 Vmp
    12 Panels x 22.7 Voc = 272 Voc
    using 0.31%/C
    COLD, 0 Degrees C, 272v + (272v x 0.31%/C x 25C) = 293 Voc (not too high?)
    HOT, 40 Degres C , 218v - (218v x 0.31%/C x 15C) = 208 Vmp (not too low?)
    Look good ?

    Will the Xantrex GT 2.8 run efficiently with 12 panels at 2,460 Watts ?

    Evergreen 205W specs ...
    114 Cells
    Power (Watts) 205
    Maximum Power, Pp,max = 210 W
    Minimum Power, Pp,min = 205 W
    Voltage, Vmp = 18.2 V
    Current, Imp = 11.27 A
    Open Circuit Voltage, Voc (Volts) = 22.7 V
    Short Circuit Current, Isc (Amps) = 11.93 A

    Temperature Coefficients
    αPmp: -0.43 %/°C
    αVmp: -0.40 %/°C
    αImp: -0.03 %/°C
    αVoc: -0.31 %/°C
    αIoc: +0.05 %/°C

    NEOH I live in northwest Pa and it gets lots colder than 0 c. here. That is equal to o degree F In my area which is east of astubula and trumble county in ohio has -22 f temp. I planned for that temp. I couldn,t find a string chart for the xantrex so used the fronuis string chart.
    fronuis 1g 2000= 11 panels @ 2256 w
    fronius 1g 3000= 15 panels @3077 w
    fronuis 1g plus 3-0-1 uni only 16 panels @ 3282 w
    the above examples are 1 string in series.
    PV Powered also has a nice string chart that I like to refer too. Just pick out an inverter that operates at the same voltage as the one you like. it gives you the voc. at the highest and lowest temp. :Dsolarvic:D
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Grid-Tie choice ?

    The GT sizing program is buried deep in the Schneider website and impossible to direct link (click through the GT product links):

    http://www.schneider-electric.com/sites/corporate/en/products-services/renewable-energies/renewable-energies.page?f=F13%3ARenewable%20Energies

    This link should be to the GT sizing tool (stripped of frames):

    http://www.schneider-electric.com/sites/corporate/en/products-services/renewable-energies/products-offer/sizing-tools-xantrex.page

    With Evergreen 205 watt panels (ES A 205 fa3) and a GT 2.8 inverter on 240 VAC line between -22F and +95F (ambient) will run between 1 string of 12-22 modules... With 13 to 16 modules in series as the optimum (with 12, the GT inverter will not harvest all power on a hot day; 17-22 modules the GT will limit to ~2,800 watts maximum output, 21-22 modules and inverter runs in 550-600 VDC range on -22F day).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NEOH
    NEOH Solar Expert Posts: 74 ✭✭
    Re: Grid-Tie choice ?

    Outback GTFX 3048 - Does anybody have any experience with this device ?

    The sales pitch ...

    "... Grid-intertied solar systems are great but the big drawback has always been that when the grid has a blackout so do you! Without batteries there is nowhere for all that solar power to go so it shuts down until the grid comes back. Now you can have your meter turn backwards and power when the neighbors are without!

    And the efficiency of the Outback Grid Tie inverters is very close to the non-battery systems! ..."

    This device appears to have two Modes...
    1) Grid Up, ATS Closed, Grid-Intertie mode - SELLS PV Power to the Grid
    2) Grid Down, ATS Open - Off-Grid Inverter powering some Loads from the 48V Battery and my PV array

    How do I connect my PV array to the 48V Battery?
    Via an Outback Flex Max 60 Charge Controller?
    I see where the 48V Battery connects to the GTFX 3048 for Off-Grid Inverter mode.

    So, I would have my PV array and the GTFX 3048 charging the 48V Battery.
    Then when the 48V Battery is in FLOAT, somehow the PV array power is then SOLD to the Grid? How does this happen?

    This appears to be a very versatile device but I do not understand how the Grid-Intertie SELL mode functions with my PV array.