Solar Setup Theory / Feasability

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marzoid
marzoid Registered Users Posts: 2
in Solar Beginners Corner #1
Good Day,

Am setting up a solar Power system. Have the following hardware

1 x FM80
1 x Mate
1 x Hub
2 x VFX3048E
4 x 220 Amp Hour 12 Volt Deep Cycle Batteries
12 x 190w Suntech Panels

I have divided the main panel up into two sub panels. The essential loads (lights / TV / cable / Internet) on one and Non-essential (Water Heater / Stove / Fridge / Kettle) on the other.

Currently I have one Outback connected to the essential loads panel with the 4 batteries. No solar panels are connected yet. It is serving as Power backup when the utility cuts power, for about 3 hours per day (random time, morning / afternoon / evening). So far it seems to be doing the job well.

Now, I am trying to bring in the Solar Panels into the equation. My ultimate plan is to have power backup to the essential loads (currently being done) , but also use the solar panels to reduce utility power usage, thereby reducing the utility bill.

What I was thinking in theory, is to have the two outback VFX3048’s connected separately. One outback will serve as power backup (essential loads / batteries / outback inverter / No solar) and the second outback (non essential loads / no batteries / fm80 / 12 x panels).

With this setup Outback no 1 will serve as a giant UPS, powering the essential items, when the utility power goes out. Outback no 1 won’t decrease my electricity bill, as the outback will use utility power to recharge the batteries, but I will have power to the essential loads 24/7

Outback no 2, will have a few non-essential loads on it. During the day, when the non-essential loads are utilized the outback will first utilize solar generated power first. Whatever balance is required will be pulled from utility power. With this setup I would reduce my electricity bill for during the day non-essential loads.

My questions to the guru’s out there are 1) does the above make sense and 2) is it feasible and 3) is there a better way of trying to accomplish the tasks above.

Apologies for the long winded post

Regards
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #2
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    Re: Solar Setup Theory / Feasability
    marzoid wrote: »
    Good Day,

    Am setting up a solar Power system. Have the following hardware

    1 x FM80
    1 x Mate
    1 x Hub
    2 x VFX3048E
    4 x 220 Amp Hour 12 Volt Deep Cycle Batteries
    12 x 190w Suntech Panels

    I have divided the main panel up into two sub panels. The essential loads (lights / TV / cable / Internet) on one and Non-essential (Water Heater / Stove / Fridge / Kettle) on the other.

    TV, cable, and internet are essential loads but your refrigerator is not?
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #3
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    Re: Solar Setup Theory / Feasability

    I don't think why this would be unfeasible. Of course, two inverters are more expensive than one.

    Your grid electricity is 240V, right? But the Outbacks are 120V. Do you have any 240V loads aming the essentials and non-essentials?
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #4
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    Re: Solar Setup Theory / Feasability
    NorthGuy wrote: »
    I don't think why this would be unfeasible. Of course, two inverters are more expensive than one.

    Your grid electricity is 240V, right? But the Outbacks are 120V. Do you have any 240V loads aming the essentials and non-essentials?
    VFX " E " models are 230v @50 hz output. The system sounds different, but a lot of them are ...... Mine is, but it works for me.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Solar Setup Theory / Feasability

    Let's try answering the questions. :D

    The first inverter will have AC available to it all the while the grid is up. This will keep the batteries charged and supply loads connected to it. When the grid goes down the inverter will handle the loads.

    The second inverter will not have AC to it all the time, but instead will power its loads from batteries. Now, which batteries? If it is connected to the same batteries as the first inverter guess what? It will draw power from the grid via the first inverter's charging circuit. Instead of reducing the utility usage you will increase it because of powering the charger on inverter #1 and running inverter #2.

    Let's add the solar charging this single battery bank. It should provide enough power to stay ahead of the needs on inverter #2 (including running the inverter and maintaining the batteries), thus eliminating the charging demand on inverter #1. But this will only happen during daylight. Once the sun goes down inverter #1 will start charging the batteries again.

    You could adjust charging settings and/or include a relay so that inverter #1 sees the grid power as a gen, engaging it only when needed. This would remove the loads on both inverters from the grid except when necessary.

    The best bet for taking some of the load off and leaving the other inverter as back-up only is to have two separate battery banks. In the event of an extended outage you could use a battery switch to tie the two banks together so that both would be charged from the panels. In that instance it would be necessary to have a large enough array to recharge both banks. At 36 Amps potential peak output your proposed array is a tad small for this.

    BTW this is an expensive way to take load off the grid. You would get the most benefit if you could use the loads on inverter #2 while the sun is shining. Otherwise all the power used will have to be stored first, and that puts the efficiency down around 50%. Pretty awful. There are probably more economical ways for you to save on electricity rather than investing a few thousand dollars into an off-grid system to handle some occasional daily loads.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #6
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    Re: Solar Setup Theory / Feasability
    marzoid wrote: »
    What I was thinking in theory, is to have the two outback VFX3048’s connected separately. One outback will serve as power backup (essential loads / batteries / outback inverter / No solar) and the second outback (non essential loads / no batteries / fm80 / 12 x panels).

    It's not possible to use an outback without batteries. The simplest configuration using this equipment would be to connect both outbacks to the battery, then the FM and solar to the batteries. I'm not 100% sure about the detailed settings possible with the outbacks, but what you could do is connect both of them to the grid, then set the battery low voltage disconnect higher for no 2 than for no 1. Another setting you'd need to configure is when the outbacks decide to charge from the grid. So by default they'll provide power from batteries unless the battery voltage drops to X, then switch to grid. Or if the loads exceed Y amps, then switch to grid.
    The scenarios would be:

    Sun shining, grid available, batteries charged:
    - Power to the loads will come from the solar and/or batteries as long as the batts are above a certain voltage.
    - If you suddenly draw a lot of current, then the outbacks will switch to grid and pass through grid power.

    Sun shining, grid unavailable, batteries at low state of charge:
    - Inverter no2 would have hit the low voltage disconnect, so would turn its output off
    - Inverter no1 would be drawing from the solar/batteries

    No sun, batteries low, grid available:
    - Both inverters would be passing through grid power to the loads and would be charging the battery simultaneously.

    An alternative to this is to connect both inverters together in a parallel configuration so that they behave like a single 6kW inverter. Then just manually turn off the non-essential loads.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Solar Setup Theory / Feasability

    Outback FX inverters switch to grid power any time they sense it on AC IN. The only way around it is to use a relay controlled by AGS circuit to connect AC IN as needed.

    He'd be better off seeing if the utility allows sell-back and getting a GFX model so that there would be battery back-up for when the grid goes down and any surplus power available from the panels would be sold to the grid.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #8
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    Re: Solar Setup Theory / Feasability
    Cariboocoot wrote: »
    Outback FX inverters switch to grid power any time they sense it on AC IN. The only way around it is to use a relay controlled by AGS circuit to connect AC IN as needed.

    Ah, thanks Mark. Both the FM and the inverters have a programmable relay which can be switched on based on battery voltage, so either of these could be used to control an external relay right?

    Pity about the limited programming in the outbacks.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #9
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    Re: Solar Setup Theory / Feasability

    Actually, you can run a Outback Inverter off any 12, 24, 48 V power supply, All you need is something to power the control board at the correct voltage.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
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    Re: Solar Setup Theory / Feasability
    stephendv wrote: »
    Ah, thanks Mark. Both the FM and the inverters have a programmable relay which can be switched on based on battery voltage, so either of these could be used to control an external relay right?

    Yes an FM's AUX control could be used to trigger it based on Voltage. The FX's auto gen start is usually what is used - it has more extensive capabilities including time regulation.
    Pity about the limited programming in the outbacks.

    I wouldn't say the programming is all that limited. They aren't GT inverters for one thing, so the "grid connect at Battery Voltage" function isn't included.

    The design is old, but dependable. More so than any other inverter out there I dare say. It is also incredibly flexible in application. You can do all kinds of things with them, providing you have the patience to work out the innumerable wiring possibilities and endless programming variables. Tend to be a bit costly, though.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #11
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    Re: Solar Setup Theory / Feasability
    Cariboocoot wrote: »
    The first inverter will have AC available to it all the while the grid is up. This will keep the batteries charged and supply loads connected to it. When the grid goes down the inverter will handle the loads.

    The second inverter will not have AC to it all the time, but instead will power its loads from batteries. Now, which batteries? If it is connected to the same batteries as the first inverter guess what? It will draw power from the grid via the first inverter's charging circuit. Instead of reducing the utility usage you will increase it because of powering the charger on inverter #1 and running inverter #2.

    I think he meant a different setup.

    He has two panels. Theres's no connection between these panels.

    Panel A is not connected to the grid and is fed by inverter A. This inverter uses solar, and grid as needed to support loads on panel A. Sort of standard hybrid system.

    Panel B is connected to a transfer switch, which lets it to be fed either by Inverter B or by a grid. Normally Inverter B is off and Panel B is connected to the grid. When there's an outage, Inverter B turns on, the transfer switch connects panel B to the Inverter B and loads on Panel B get power. Inverter B never charges any batteries, uless a generator is connected.

    Of course inverter A gets its grid power directly from the grid, so when Inverter B is on, it cannot feed any power to Inverter A.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
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    Re: Solar Setup Theory / Feasability

    I'd be lying if I said I understood that. Sounds like an opportunity to mis-wire AC and DC and have redundant transfer switches and generally get into a of trouble. :roll:
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  • marzoid
    marzoid Registered Users Posts: 2
    #13
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    Re: Solar Setup Theory / Feasability

    Thanks for the replies.

    On the Fridge being not being essential. It is. I just haven't moved it yet from the non-essential panel to the essential panel. When i started, all loads were on the non-essential panel. Then i would place a ekm digital meter on each load for a period of a few days to establish a 24hr consumption baseline. Once the baseline is established for each load, i will move it over to the essential panel.

    As it stands, both my subpanels (essential and non-essential) are fed via grid power. Which goes out for a hour or two, or 3 daily.

    The essential sub-panel is connected to a single outback, with a battery bank. This achieves my first goal, of Power backup for the essential loads when the grid goes down.

    This is where my flawed thinking starts :) As stated above the non-essential panel is entirely powered by the grid. (when available). I'm not looking for Power Backup on the 2nd Outback .In a bid to reduce my monthly utility bill , i was thinking along the lines of running the non-essential loads through the 2nd Outback. The 2nd Outback won't be connected to any battery bank. The 2nd Outback will be connected to the FM80, which will have the 12 x solar panels feeding it. I assumed, that the Outback could be set to use the Solar Power generated first, and use grid power for the balance.

    Looking at the replies it seems, that this is not a good way of doing it, or that it can't be achieved with Outback inverters.

    Back to the drawing board......
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #14
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    Re: Solar Setup Theory / Feasability
    marzoid wrote: »
    In a bid to reduce my monthly utility bill ...

    Unless your electricity is very expensive, it's very hard to reduce your bill.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
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    Re: Solar Setup Theory / Feasability
    marzoid wrote: »
    The 2nd Outback won't be connected to any battery bank.

    Then the 2nd Outback will do absolutely nothing. They don't work without batteries.

    Neither will a GT inverter which is powered directly from panels work, as they have to be connected to the grid on the output side to function. In fact this sounds more like what you are trying for: back-feeding from a GTI to off-set utility power usage.
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