I'm diving into Grid Tie

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  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: I'm diving into Grid Tie
    Well, today I received the GREAT news. SCE has approved my site for generation. I'll be online starting tomorrow…

    Well, at the conclusion of day 1 of my system, I produced 27 kWh of power (4180 W of DC). I consumed 14 kWh so I pushed 13 kWh back onto the grid.
    :cool::cool::cool:

    Jim / crewzer
  • wilsonbhwilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: I'm diving into Grid Tie
    autoxsteve wrote: »
    Well, at the conclusion of day 1 of my system, I produced 27 kWh of power (4180 W of DC).

    I consumed 14 kWh so I pushed 13 kWh back onto the grid.

    For comparison purposes, Mike90045 produced 21.4 kWh (with 4576 of DC) and Magneto produced 26.1 kWh (with 4620 of DC). Finally Mike Brown produced 32.4 kWh (with 5000W of DC).

    Sounds like I'm doing ok with a smaller system altho it is new....


    That is awesome!!! I'm in the process of building my system very similiar to your setup, with some exceptions like using a Xantrex inverter instead of the Fronius. But the panels will be the same.

    Are your panels facing south? I don't have sufficient roof space for 22 panels to be setup on the south side of my house. I have to put one 11 panel string on the west or east side. I'm at latitude 28 degrees.

    If every house in America did solar, we could wean ourselves off foreign oil!!!
  • BB.BB. Super Moderators, Administrators Posts: 29,002 admin
    Re: I'm diving into Grid Tie

    Wilsonbh,

    I have always wondered if running one string facing south and another string facing east/west, how a single input grid tie inverter would respond vs two inverters on the two different strings.

    Looking around, found a Fronius FAQ (PDF File) that goes through the numbers on losses between optimum + non-optimum string orientations (also talks about losses due to shading). I assume the test results would be similar for any well designed grid tied inverter (Vmpp between the two strings are almost the same once both strings reach a minimum amount of solar irradiance needed to generate substantial power).

    Looks like paralleling two strings with different orientations into one inverter gives about the same results as running into two different inverters. There is roughly a 1% loss in total panel power output when using 1 inverter vs 2--which is probably swamped by the additional tare losses required to run two inverters vs one inverter.

    I would check with Solar Guppy--he has lots of experience with these issues. If I recall correctly, his recommendation was, if there is a choice, to run the non-optimum string on the east side of the home as you get more power with cooler panels (cooler in AM vs PM).

    Other things to consider though--1) do you have morning or evening marine layer (fog) conditions. And/or 2) will you be using Time Of Use metering--in my case, my TOU rate is 3x for noon to 6pm vs other times (so, most likely I would get better offset rates with a west facing array). And lastly, the site with the least shading during optimum sun angle will probably output the most power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: I'm diving into Grid Tie

    As long as the two stings have the same number/type of panels, running one east and the other south will work fine. I've run, south-sout east, south south west parrallel and have hard data to confirm this

    For the OP, put one string east, the other south and you will get the best production, as BB wrote, east for Florida is ideal as the summer weather by midday and onward you get our daily thunderstorms in the rainy season.
  • wilsonbhwilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: I'm diving into Grid Tie
    As long as the two stings have the same number/type of panels, running one east and the other south will work fine. I've run, south-sout east, south south west parrallel and have hard data to confirm this

    For the OP, put one string east, the other south and you will get the best production, as BB wrote, east for Florida is ideal as the summer weather by midday and onward you get our daily thunderstorms in the rainy season.

    This is what I will do. I'll have 22 Evergreen 190s. Plan to mount them, 11 south and 11 east. It looks very very simple to install if I use the Xantrex GT4. Will FPL require an AC and a DC disconnect if I use the Xantrex considering that it has these built in? Would be nice if this was not required.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: I'm diving into Grid Tie

    You need to contact FPL to check out ALL the details for interconnect.

    The Xantrex GT series meet all required codes for disconnects, I have none on my 3 units and just use the built in disconnect, btw, its your county and power companys that have the final say on what is required.
  • wilsonbhwilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: I'm diving into Grid Tie
    You need to contact FPL to check out ALL the details for interconnect.

    The Xantrex GT series meet all required codes for disconnects, I have none on my 3 units and just use the built in disconnect, btw, its your county and power companys that have the final say on what is required.

    Understand...

    The FPL guy I corresponded with on this said that once the interconnect agreement is signed and the system installation is ready, they will come out and install an additional meter to capture the electricity I would be making. Sounds like an inefficient way to do this. Why not just swap out my existing meter I was wondering, if it can't handle net-metering. I want as little hardware installed as possible.

    Did FPL add a meter to your system or did you use the existing meter?
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: I'm diving into Grid Tie

    I am not in FLP customer ... I have an electronic meter that records the flow in seperate registers for buy/sell. This give Lakeland Electric postitive numbers for both and on their billing they subract one from the other after taxes and fule costs are applied, its close to net-metering, but not quite as I don't get credited for county taxes on the power I sell back. On the other hand, I get my net electric to offset my water ( when I net produce more than used as I am doing this time of year ) as there billing is combined, so overall its a good deal.

    Sounds like FPL is going to install a second meter and only pay you wholesale, in Florida its there choice to support netmetering and the choice is the power companys. If they don't go netmeter, at their cost they are required to install a second meter. You need to find out for sure from FPL what they will do as only they know the answer.
  • BB.BB. Super Moderators, Administrators Posts: 29,002 admin
    Re: I'm diving into Grid Tie

    One issue you may have with your AC disconnect is access to the switch itself... Mine GT inverter is installed in a locked garage (weather tight, cool, and secure). So--installing a remote switch next to the meter made sense.

    If you can hand wave that your inverter is accessible (and not guarded by 10 starving pit bulls)--you should have good luck.

    In any case, it sounds like you need some details from FLP to ensure that everything is wired to their requirements.

    Also, if they only pay for wholesale power--that sounds like lesser deal for you. :cry:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wilsonbhwilsonbh Solar Expert Posts: 57 ✭✭✭
    Re: I'm diving into Grid Tie
    BB. wrote: »
    One issue you may have with your AC disconnect is access to the switch itself... Mine GT inverter is installed in a locked garage (weather tight, cool, and secure). So--installing a remote switch next to the meter made sense.

    If you can hand wave that your inverter is accessible (and not guarded by 10 starving pit bulls)--you should have good luck.

    In any case, it sounds like you need some details from FLP to ensure that everything is wired to their requirements.

    Also, if they only pay for wholesale power--that sounds like lesser deal for you. :cry:

    -Bill


    I've got a call into the FPL representative. Florida Power & Light will probably only pay wholesale as they want to install a second meter next to the existing one. That sounds like different rates to me!

    I still think our power companies and the gov't doesn't REALLY want us to make our own power. But they want to look politically correct so they play the game. If they really wanted to encourage the use of solar power, there would not be so many hurdles to jump over and so little documentation on the subject. Still, I'm going to research this thing to the maximum extent possible and if it appears feasable, I'm going to do it.

    It could be really simple to install....panels wired to inverter, then the inverter wired to it's own circuit breaker in my main panel box - DONE!

    Once the FPL guy contacts me, I'll post what he says here for others to read.

    UPDATE FLASH: FPL just called me. A new law was passed in Florida recently which mandates some changes to Grid Tie systems. After the details of this new ruling are approved (May or June), then no 2nd meters and they change the existing meter to a digital. The electricity is credited if excess is created, at the same rates purchased. Additionally, AFTER this ruling is approved, disconnects before and after the inverter are not required if the inverter has these build into its hardware (Xantrex).
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