Battery Backup and Grid Tie, How many folks are doing this NOW.

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Solarman
Solarman Registered Users Posts: 9 ✭
in Solar Beginners Corner #1
Switch between one another as needed. Tell me what you have and how your doing it.

I've always loved the idea of solar power, something for nothing, (well not nothing but you know) I guess you could say, as long as our star shines, electrical power is free power.

I'm using a grid tie 300w and a battery bank of 12v 450ah coupled with 520 watt of PV to mostly experiment on how the whole thing works together right now. I'm using 30amp breakers as switch's to switch between the grid tie and batteries and charge as needed, or put power into the house as needed, but I put my batteries as a priority #1, after that, I just flick a switch and go to the grid.

What's everyone else doing on my level? That's my question.
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  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    #2
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    http://forum.solar-electric.com/showthread.php?25105-Battery-vs-generator
    I'm trying to sort out the same thing. Good luck and let me know how it works out for you!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    Something for nothing?
    No, more like the same thing for 5-10 times the price of grid power.

    Grid-tie makes sense when you do it on a large scale; the installation is about the same amount of hassle but you generate more power to offset use and any tax rebates/incentives go up as well.

    Battery back-up makes sense when you do it on a small scale; lower capital investment and not as much repeat expense for replacing batteries.

    These may seem diametric, but there's nothing that says you can't have both a standard GTI system and a small hybrid GTI system for critical loads.
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  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    #4
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    I have a smallish "semi-offgrid" system (2kW in panels, 48V 390AH battery bank, Outback gear) that runs a sub panel to which I moved the six "critical" circuits in my house. I could run them totally off-grid if necessary, but since my normal loads in the back room (several computers) add up to a fairly large chunk of power I switch between grid and inverter daily. The batteries get exercised but not heavily so each day.

    I contemplated grid-tied when I put the system in and decided not to. It just isn't worth it for a couple of reasons.

    First, and perhaps peculiar to me, is that this is a hobby for me. I enjoy tinkering with stuff like this and I'd have a hard time tinkering much if I had to have engineers and the power company sign off on it every time I did something. Not to mention the idea that I have to get their approval rankles me anyway...

    Primarily, though, it just wasn't worth it. My local utility had a grid-tie plan available but it was only kWh-for-kWh, no adjustment for time of day, and they would NOT pay for excess power, it was use-it-or-lose-it. The bill would never go below a certain amount, since you couldn't offset the base charge and other fees. To add insult to injury they added a fee for the smart meter that would have put me in the negative to begin with! (Of course now we all have the smart meter, whether we wanted it or not.)

    Now I have yet another reason to be glad I didn't go grid-tied as the utility company has managed to get a bill through the legislature allowing them to begin charging - oh, good grief, not again - ANOTHER fee "to reclaim more of their fixed costs".

    If all I had wanted was "emergency power" I'd never have put all this in, as Coot said a generator is far cheaper (and I got one of those as well!) but my system has basically become a (nearly) whole-house UPS. The only way I know a power bump has occurred is that the clock on the microwave (not on the inverter) has reset. I also know myself - if I relied solely on the generator it probably wouldn't work if/when I need it, "out of sight out of mind". With the solar system I see / use / test it daily. And, as I said, it's a hobby!

    This reminds me (yet again) that I haven't tested the generator in a while... Need to get it out and make sure it still runs...! :blush:
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  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    #5
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.
    First, and perhaps peculiar to me, is that this is a hobby for me. I enjoy tinkering with stuff like this and I'd have a hard time tinkering much if I had to have engineers and the power company sign off on it every time I did something. Not to mention the idea that I have to get their approval rankles me anyway...


    Almost exactly my reasons for not grid tying.
    Primarily, though, it just wasn't worth it. My local utility had a grid-tie plan available but it was only kWh-for-kWh, no adjustment for time of day, and they would NOT pay for excess power, it was use-it-or-lose-it. The bill would never go below a certain amount, since you couldn't offset the base charge and other fees. To add insult to injury they added a fee for the smart meter that would have put me in the negative to begin with! (Of course now we all have the smart meter, whether we wanted it or not.)

    My utilitee did have a $2 per watt rebate which they have now ended but in my case I still go with your first quote that I highlighted.
    gww
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #6
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    I run a 12.5 Kw grid tie system that covers a large percentage of my consumption with net metering, rather than batteries which would limit my load capability I would do a generator. That being said I have no generator because my utility is so reliable I can't remember the last time we had an outage of more than a few minutes. In my case I would need at least a 10 Kw generator so I could keep the A/C operational in mid summer, it is almost impossible to fathom living here without A/C. I figure with batteries I would need about 36 Kw of panels and a whole bank of fork truck batteries to replace the summer grid loads which have been recorded as high as 131 kWh per day when the outside temps reach 115F-120F.

    Edit: I am not totally without generator capability, I have the Chevy Volts able to provide about 1000 watts each off the 12V system, probably enough to keep the fridge and freezer operational.
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  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    #7
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    s-d
    My air conditioning cost are the same as yours and I am not living with out it. My grid also never goes down. I did play with a small one room air cond. that seemed to draw about 800 watts. I was going to use it for a couple hours after my battery reached absorb but didn't find my summer production being as much as my winter. In winter I get above 5000watts coming in but in summer it is more like 4500 watts. My panels never reach rated output but maby a couple minutes of cloud edge effect. The mate gives really bad readings so most is just a guess but the window air didn't work well even to help a little.
    gww

    PS I have not even tried to hook up my 5000 watt generator. would like to use it to charge 48 volt battery some day though.
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  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    #8
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    As you can see from my signature I am using my system as a UPS. During sunny days I figure I am running on battery and array for some loads; refrigerators (1@120VAC & 1@24VDC), freezer (full size chest 120VAC), pellet stove and central propane gas heater, plus clocks and appliances when needed. My inverter meter shows about 3 or 4 amp load most of the time. My normal grid electric consumption is about 500kw per month; this includes 220VAC water heater, well pump and AC, that are entirely on the grid. I do have the capability of running my well on inverter power by switching to my T-220 step up transformer if the grid goes down for too long.
    The way we know the grid was down is the lights flicker when the grid comes back up and starts bulk charging the battery bank. The SW4024 is automatic.
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  • Solarman
    Solarman Registered Users Posts: 9 ✭
    #9
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    Re: Battery Backup and Grid Tie, How many folks are doing this NOW.

    Its good to run your generator at least every 2 months to keep everything flowing, keep fresh gasoline around all the time too. I have 2 genies also.

    It is a hobby for me. But its also a nice little backup system for when the gird does fail. We had a bad ice storm last year that lasted for about 5 days. I had nothing then, no generator or Solar backup. I swore I will never be caught with my pants down, ever again.

    People were leaving their houses on our street. I need to be prepared, and now I am fully prepared.
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