Question about grid tie feedback

newsunn
newsunn Registered Users Posts: 4
in Grid Tie and Grid Interactive Systems #1
Hello, I'm very new to solar so bear with me here. This may be a silly question. My situation is my local coop has nobody currently feeding back the grid with solar and I believe is a little reluctant in working with me in doing so. So in order to get my system up before the end of the year to get the federal tax credit I just want to avoid dealing with them until later. I would like to install my panels and feed my house whatever they make in the day and pull from the grid at night. If it should make more power than I need in the day I do not want to send any power back on the grid and have to deal with the electric company. Is there such a device to put between my circuit panel and my outside electric meter to prevent power from feeding back to the line if I should make more than I need, but allow me to pull as much power as I need when I need it, mainly at night? Thanks for any help.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Question about grid tie feedback

    Welcome to the forum.

    Short answer: no.

    A standard GT system takes whatever power the panels can produce and sends it into the house wiring. There it is either consumed by the household loads or, if those don't use all of it, feeds back to the grid. There's no simple way of stopping that. This is an issue that has come up before here and got into quite a long and complex discussion, with now easy resolution.

    The simple resolution is a hybrid system that uses a battery-based GTI and can have sell "shut off" so that it never feeds the household or grid. Then some loads are placed on it, and if they exceed its capacity extra power can be drawn from the utility. Expensive and somewhat inefficient.

    So we'll go with the standard question of "why do you want to do this?" and see what happens! :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Question about grid tie feedback

    welcome to the forum.
    anytime you would send power to the grid it would be because you aren't using that much. if you don't use that much during the dusk times then it will accrue. no inverter can guess let alone know what you will use up. if this is a daily breakeven you wish for you will have to follow what is going out and be sure to find a large enough load to run for whatever time it needs to to break even. same goes for monthly, but it may be harder to use it up at the end of the month at times all that has accrued, but if you have a much smaller gt system then it may go unnoticed as it will only reduce your bill some. remember too that during the summer you will have far more power generated than during the winter so if you try to break even or even come close to eliminating a winter bill that the summer will have quite a bit of excess being sold.

    that said, do know that you could get in trouble if you put in a system without approvals from all involved.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #4
    Re: Question about grid tie feedback
    newsunn wrote: »
    Hello, I'm very new to solar so bear with me here. This may be a silly question. My situation is my local coop has nobody currently feeding back the grid with solar and I believe is a little reluctant in working with me in doing so.

    Be careful, while 'net metering' is the law of the land, I think by executive mandate, it came with no enforcement, so Your local COOP can make it a pain, ignore you or make you jump through too many hoops to make it worthwhile.

    I live in Missouri and we just had an incentive passed to have electric companies get a percent of their power from renewable resources. So things may change here, but when I originally talked with my COOP that already charges a $25 a month user fee(before you buy any electric) wanted a second meter, wanted annual inspection at my cost, a second fee for the second meter and basicly ddin't want a grid tied system, to date I don't think they have one.
    newsunn wrote: »
    ...So in order to get my system up before the end of the year to get the federal tax credit I just want to avoid dealing with them until later...

    If your solely worried about the tax rebate, the key wording has to do with putting the system into use. You may not be able to do this with the grid tie inverter, but might be able to do a water preheater, with a cheap Modified sine wave, inverter. It would cost you some money though. If you intended to have a battery backup with the grid tied system, there would be minimal extra cost to run power to some unconnected outlets. But these systems are not cheap and likely not what you had in mind.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #5
    Re: Question about grid tie feedback

    I had it out with my Coop also. While they already had a couple of one or two panel systems assisting something they had no experience with a 8.2 KW system. In the end it was a 6 page agreement and visit to change the meter. I had more hell with their antiquated billing system. That took over a year to get straightened out. They had to hire a IT firm to re-write software, in the end they they admitted it was to their benefit.

    One problem you can have is if you have a " Smart Meter " on your house, it will record your production as a draw and you'll be billed for what you produce. It takes a special " Net Meter " to be installed.

    Here is what I had to have.

    1) Data Sheets on all installed equipment ( for coop file )
    2) Line Drawings of the system ( for coop file )
    3) Electrical Inspection ( County Inspection from the Permit for the system ) He walked to the box and put a new sticker on it, never looked at anything.
    4) Coop Agreement signed and the system tested for Anti-islanding when Meter was changed.

    My stupid City made me have a Structural Roof analysis done by a Engineer even though they had NO regulations requiring it. The install was exempt under their rules for even requiring a permit. It was easier to have done then fight with them.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #6
    Re: Question about grid tie feedback

    By the way, my Coop will not Buy any power from me. They " Bank it " and I can use it as I see fit. I have over 3,000 KWH banked, I just burn it off with space heaters, not really efficient but it's a cheap way to use it.

    They charge me $9.00 a month + the tax on what they supply back to me or a total of $10.30 a month or so.
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  • newsunn
    newsunn Registered Users Posts: 4
    #7
    Re: Question about grid tie feedback

    Would the battery charged systems work for me if I used a generator transfer swithch to power some of my circuits? I was originally wanting a 10k grid tie but would be happy to settle for half that just to get started. Is the Outback inverter system the way to go? Any recommendations? One more newbie question. What happens when your batteries are topped off and your not needing any more power? Sorry if that is a silly question. I do appreciate the help.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Question about grid tie feedback
    newsunn wrote: »
    What happens when your batteries are topped off and your not needing any more power? Sorry if that is a silly question. I do appreciate the help.

    What happens is that the charge controller stops sending full power to the batteries. As long as there's power available from the panels, it will try to maintain Float Voltage against the draw of the loads. When there's no longer enough panel power to achieve this the batteries will make up the difference. The next day (hopefully) the charge cycle starts anew.

    As before, we really need to know why you want to do this. Off-grid power comes at a very hefty price compared to grid power. The usual reason people install GT systems is because the circumstances are right to make it economically feasible (tax rebates, utility purchase rates, et cetera).

    You can reduce your electric bill with solar, but that's not always the same thing as saving money.
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  • newsunn
    newsunn Registered Users Posts: 4
    #9
    Re: Question about grid tie feedback

    The reason I wanted to avoid selling back to the grid at the moment is because I don't think they will approve me by the end of the year. I have the same requirements as Blackcherry04 mentioned above. They want my system designed by a engineer and then they have several days to either approve my system or not. I called the IRS and the lady I talked with said the system had to be running this year for me to take advantage of the tax credit. The tax credit is what I'm wanting. Grid tie is the way I would like to go but If I could put up a battery backup system to power a few circuits that would be fine for now. It would be nice to have that for power outages.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #10
    Re: Question about grid tie feedback
    newsunn wrote: »
    The reason I wanted to avoid selling back to the grid at the moment is because I don't think they will approve me by the end of the year. I have the same requirements as Blackcherry04 mentioned above. They want my system designed by a engineer and then they have several days to either approve my system or not. I called the IRS and the lady I talked with said the system had to be running this year for me to take advantage of the tax credit. The tax credit is what I'm wanting. Grid tie is the way I would like to go but If I could put up a battery backup system to power a few circuits that would be fine for now. It would be nice to have that for power outages.
    A couple of things...

    First, the inverter you would buy for a straight grid tied system and one you would buy for a battery back up are not the same.

    Second, batteries are very expensive.

    Third, you can't connect an inverter to your house wiring if your house is also connected to the grid whether you push power onto the grid or not without dealing with your electric co-op. Not legally, anyway.
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  • newsunn
    newsunn Registered Users Posts: 4
    #11
    Re: Question about grid tie feedback

    What kind of insurance does everyone have? It was suggested I have insurance by the coop if I'm grid tied to cover any possible feedback liability. So I checked with my insurance company and of course they don't want to cover it.

    PV engineer,
    Do people that have backup generators connected to there house using a transfer switch have to have an agreement with there coop?
    The reason I'm asking all the questions is because I want to do things right.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #12
    Re: Question about grid tie feedback
    newsunn wrote: »
    PV engineer,
    Do people that have backup generators connected to there house using a transfer switch have to have an agreement with there coop?
    The reason I'm asking all the questions is because I want to do things right.
    I don't have any direct experience with that, but I don't think so because the generator is never connected to the grid. The house is connected to either the grid or the generator but never both at the same time.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #13
    Re: Question about grid tie feedback
    newsunn wrote: »
    What kind of insurance does everyone have? It was suggested I have insurance by the coop if I'm grid tied to cover any possible feedback liability. So I checked with my insurance company and of course they don't want to cover it.

    PV engineer,
    Do people that have backup generators connected to there house using a transfer switch have to have an agreement with there coop?
    The reason I'm asking all the questions is because I want to do things right.
    Your Homeowners would automatically cover the Liability, unless it has some kind of exclusion. A back up generator wouldn't be back feeding into their system, not their business. For that you'd just have to get a Electrical inspection from the permit you pull, unless you just boot leg it.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #14
    Re: Question about grid tie feedback

    I just added everything to my homeowners for a very nominal increase in the coverage/premium, full replacement costs. The liability part should be covered by your homeowners and my insurance company understood the risk to the grid was low with the anti-islanding provided in modern grid tie inverters.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #15
    Re: Question about grid tie feedback
    ggunn wrote: »
    I don't have any direct experience with that, but I don't think so because the generator is never connected to the grid. The house is connected to either the grid or the generator but never both at the same time.

    If there is NEC code enforcement or equivalent inspection associated with a permit, the co-op would be assured that you have correctly installed a proper transfer switch for your and their safety.

    If there is no AHJ inspection, then the co-op might reasonably insist on looking at the transfer switch arrangement themselves. (If they find out about it, that is.)
    SMA SB 3000, old BP panels.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #16
    Re: Question about grid tie feedback
    inetdog wrote: »
    If there is NEC code enforcement or equivalent inspection associated with a permit, the co-op would be assured that you have correctly installed a proper transfer switch for your and their safety.

    If there is no AHJ inspection, then the co-op might reasonably insist on looking at the transfer switch arrangement themselves. (If they find out about it, that is.)
    You're probably right. I just meant that they probably wouldn't have to have an interconnect agreement.
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