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Thread: Non-Net Metered PV system- Grid Tied

  1. #11
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    Quote Originally Posted by BillK-AZ View Post
    I understand that this is a common problem in Hawaii wherein the grid can not accept more PV input at this time. I attended a Solaredge presentation that showed they have a metering option that communicates to some of their inverters and eliminates backfeed to the utility. No direct experience.
    So, what do the customers do with all that solar? Are they getting paid for simply having the panels on their roofs??

  2. #12
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    Quote Originally Posted by gadfly56 View Post
    So, what do the customers do with all that solar? Are they getting paid for simply having the panels on their roofs??
    Hawaii is a special case because they have their own very small grid which is subject to instability if too much DG gets fed into it. I don't know if solar owners are getting paid for anything but they have to use all the kWh that they produce.

  3. #13
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    Quote Originally Posted by ggunn View Post
    Hawaii is a special case because they have their own very small grid which is subject to instability if too much DG gets fed into it. I don't know if solar owners are getting paid for anything but they have to use all the kWh that they produce.
    Basically a GTI in Hawaii must now be able to throttle back its power output to prevent backfeeding the grid either by configuration or when given that command by POCO. When that happens the GTI simply does not draw full power from the panels, so there is no power looking for a load. The potential solar PV energy is just not used.
    Nobody gets paid for power not produced.

    Some homeowners may choose to turn on elective loads, such as resistance water heating, to get some benefit from the potential power.

  4. #14
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    look into a beckwith relay protection panel. they are often used for CHP plants that cant backfeed.

  5. #15
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    Design it for output

    Personally, I would design my system to output 24k and oversize the array.

    What I mean is max the inverters output at 24k, or 2 inverters most likely. But don't stop there, oversize the array, so that you are putting out 24k more often, thus maximizing your output. If you don't oversize the array it hardly ever will produce max except at the peak of the day (think bell curve). Oversized think bell curve with cut off, instead of just at peak time, you could get hours of maxed output. I have designed several this way with no problems.

    Sorry, I read further, I didn't realize that you can not feed back to the grid at all, that would be a problem, short of going pure off grid.

  6. #16
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    double check

    I would double check with the utility and make sure you understand them clearly.

    The entire point of net metering is that your excess power goes to the grid. If you are grid connected your net metering, now the pay structure is a whole different thing. I mean that is basically the definition of it. At night or whatever then the meter turns the other way. Sorry ranting that is where your are stuck.

    So if a system is not net metering, basically your off grid or a hybrid, which still involves an off grid component and storage.

    There are situations I have run into with various funny rules, in some cases the utilities did not want to buy excess power, but that was on a yearly basis, not real time. If you can not feed back at all, then that is not net metering, and your stuck. The switch idea you propose won't work well, your system will be going on and offline all the time, as it would need to scale back production intelligently and then start production.

    Much better to build an off grid system, even if you have the grid to fulfill shortages. In that ways you produce, store and use your power, but you won't give it back to them. It will also make much better use of your power, and will lower if not eliminate your bill.

    Just my opinion. Let me know though, we can figure out a way to make it work well for you.
    Last edited by seaton; 09-06-17 at 10:27 AM.

  7. #17
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    Quote Originally Posted by seaton View Post
    I would double check with the utility and make sure you understand them clearly.

    The entire point of net metering is that your excess power goes to the grid. If you are grid connected your net metering, now the pay structure is a whole different thing. I mean that is basically the definition of it. At night or whatever then the meter turns the other way. Sorry ranting that is where your are stuck.

    So if a system is not net metering, basically your off grid or a hybrid, which still involves an off grid component and storage.

    There are situations I have run into with various funny rules, in some cases the utilities did not want to buy excess power, but that was on a yearly basis, not real time. If you can not feed back at all, then that is not net metering, and your stuck. The switch idea you propose won't work well, your system will be going on and offline all the time, as it would need to scale back production intelligently and then start production.

    Much better to build an off grid system, even if you have the grid to fulfill shortages. In that ways you produce, store and use your power, but you won't give it back to them. It will also make much better use of your power, and will lower if not eliminate your bill.

    Just my opinion. Let me know though, we can figure out a way to make it work well for you.
    There are situations where you are not allowed to backfeed the grid at all, ever. Around here such is the case if your interconnection is on the downtown grid. If that is your situation then you must come up with a way to power only your local loads (partially or fully) from solar. Off grid? Well, yes, that is one way to do it, but off grid power is much more expensive than grid power, usually on the order of 10X as much, so you'll have to look at the economics and decide if it is worth it.

  8. #18
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    Quote Originally Posted by ggunn View Post
    There are situations where you are not allowed to backfeed the grid at all, ever. Around here such is the case if your interconnection is on the downtown grid.
    Out of curiosity, how does that fit in with net metering laws? Is there no net metering there or were the utilities allowed exceptions for certain areas?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #19
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    Quote Originally Posted by electrofelon View Post
    Out of curiosity, how does that fit in with net metering laws? Is there no net metering there or were the utilities allowed exceptions for certain areas?
    Net metering isn't a law, at least not in Texas. It's a tariff administered by the AHJ and they are free to amend/implement it as they see fit. In (at least) Austin and San Antonio, in the part of the city designated as the Downtown Network you cannot export power to the grid at any time.

  10. #20
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    Quote Originally Posted by ggunn View Post
    In (at least) Austin and San Antonio, in the part of the city designated as the Downtown Network you cannot export power to the grid at any time.
    So on a technical level, what's different about the Downtown Network that makes it harder for the POCO to handle backfeed there?

    Thanks, Wayne

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