Help needed to build a Hybrid System

Nawam
Nawam Registered Users Posts: 5 ✭
in Solar Beginners Corner #1
Hello,
I am a newbie to solar and was just wondering if someone could help me with my project.
I am planing for a hybrid system which includes solar panels as well as the NEA one.
The NEA specifications, as far as I know are given below:
Volate- 220V
Current- 6 Amps
Now I am planning for a system of about 1kWh per day, say i have about 4 hours of electricity from the NEA. :p
Now what would be my ideal battery configuration for this system?? Would 24V setup be better than 12V one?
Also since the NEA voltage is huge compared to the solar, do i need to use a high voltage inverter or what ?
And what about the charge controller ??
Right now I only have these questions. I am sure if someone answers them I'll ask more. :p
Thanks in advance ..
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  • kellylipp
    kellylipp Registered Users Posts: 21 ✭✭
    #2
    Re: Help needed to build a Hybrid System

    OK, I'll bite: what an NEA? Googled and came up with Near Earth Asteroid. I'm thinking that's probably not right: lots of energy but hard to harvest efficiently or safely...

    Lots of the bigger dogs will jump in and ask about what you are trying to accomplish with this system paying particular interest to the loads you will experience. Also where on the planet are you so one can tell about how much sun you might get.

    Kelly
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Help needed to build a Hybrid System

    Welcome to the forum.

    I think you may have the specs wrong on that panel. 220 Volts? :confused: Are you sure that's not 220 Watts? At 6 Amps that would be 36.6 Vmp which is much more like what we'd expect. If that really is the Voltage it isn't going to work with any charge controller except one: the $1,200 Xantrex XW 600 MPPT 80. Frankly I'd avoid that panel in such a case because you can buy quite a few "conventional Watts of panel" for the money difference in controllers.

    To get 1 kW hour in 4 hours is fairly easy; it's an average of 250 Watts per hour. If you mean 1kW hour AC output, this would mean you need about 480 Watts of array. More is better, as the sun does not always shine brightly.

    1 kW hour per day AC can be done on a 12 Volt system without difficulty. The only caveats are that the loads should not be "1000 Watts for one hour", for example, and that you should think about the likelihood of them increasing over time. Once you pick a system Voltage you're pretty much stuck with it unless you re-design and change batteries, inverter, and possibly charge controller and panels as well. It can get messy and expensive. Normally I recommend going with 24 Volt unless there's a specific need to stay with 12 for just those reasons.

    Here's a piece about system Voltages and why you'd pick one over another: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

    Did that help?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #4
    Re: Help needed to build a Hybrid System

    Welcome to the Forum Nawam.
    Nawam wrote: »
    Hello,
    I am a newbie to solar and was just wondering if someone could help me with my project.
    I am planing for a hybrid system which includes solar panels as well as the NEA one.
    The NEA specifications, as far as I know are given below:
    Volate- 220V
    Current- 6 Amps
    Now I am planning for a system of about 1kWh per day, say i have about 4 hours of electricity from the NEA. :p
    Now what would be my ideal battery configuration for this system?? Would 24V setup be better than 12V one?
    Also since the NEA voltage is huge compared to the solar, do i need to use a high voltage inverter or what ?
    And what about the charge controller ??
    Right now I only have these questions. I am sure if someone answers them I'll ask more. :p
    Thanks in advance ..

    I think Nawam is from Nepal, so NEA is probably something like the Nepal Energy Association or similar...

    Back to the question... More or less think of a battery bank (lead acid batteries, similar to car or truck batteries but designed for "deep cycling") is the heart of your system. Typically the battery bank is around 12, 24, or 48 volts.

    And you have two sections that attach to the battery bank... The first is the Solar (or generator, wind turbine) that recharges the battery bank. And the second is your loads.

    If you have lots of low voltage DC loads (12 volt and 24 volt "devices", lighting, etc. are common)--You could just power your loads from your battery bank.

    If you have needs for other loads (more lighting, pumps, washing machine, refrigerator, etc.)--Then you would usually want a power system that outputs your local AC electrical power--Guessing 220 VAC at 50Hz.

    The device to take 12/24/48 VDC from your battery bank and convert it to 220 VAC @ 50 Hz is called an "inverter" or AC Inverter. It takes the DC voltage (and current) and "chops" it into AC voltage/current (power) (we call this power conversion as "inverting" -- slang).

    It is a "black box"--You connect your battery bank to the AC inverter and it will output 220 VAC to power your AC loads...

    Of course, there are the details... How much 220 VAC power do you need, and how many hours will you be using that per day... a 220 VAC at 6 Ampere Inverter will be roughly:

    220 VAC * 6 amps = 1,320 Watt output

    Depending on your loads, energy needs, etc... You would need a 12 volt battery bank minimum, and possibly a 24 volt battery bank (or even 48 volts) to keep the wire size "reasonable"... I like to aim at ~100 amps nominal as the maximum current to put through your DC wiring (100 amps * 12 volts = 1,200 watts).

    There are other reasons to have a higher voltage battery bank--Another one is that Charge Controllers are usually rated in output current (say 60 amps maximum at 12-48 volts). A single charge controller can "manage" a larger solar array if the battery bank is at a higher voltage--For example:

    12 volts * 60 amps = 720 watt solar array
    24 volts * 60 amps = 1,440 watt solar array
    48 volts * 60 amps = 2,880 watt solar array

    There are a lot more details to discuss--But I would suggest a good understanding of your loads and how much sun (and/or wind) per day you get for your region--Typically by month or season (and if your loads vary by season too).

    Normally, the design process would be:

    1. Conservation--Always cheaper to reduce your loads with very efficient devices (LED lamps, low power laptop computer, efficient refrigerator, etc.) than to generate power
    2. Measure your loads--Peak Watts, average watts, daytime/nightime usage, seasonal variation, special loads like motors, pumps.
    3. Use loads to design battery bank (voltage and AH capacity)
    4. Use Battery bank to estimate size of solar array (and or other charging sources)
    5. Use loads (Watt*Hours or Amp*Hours @ what voltage per day) to size solar array (how many "hours of sun" per day do you get, by season)
    6. Start selecting Batteries, Charge Controllers, Inverters that may meet your needs.
    7. Check costs/options--does system meet your needs (on paper)... Review/update
    8. Then think about spending your money on actual hardware.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #5
    Re: Help needed to build a Hybrid System
    Cariboocoot wrote: »
    Welcome to the forum.

    I think you may have the specs wrong on that panel. 220 Volts? :confused: Are you sure that's not 220 Watts?

    My guess is that NEA=POCO (update: Nepal Electricity Authority) and he is not talking about any kind of panels, just what limited power is available from the wired utility. 220 volts AC at 6 amps is not much, but for a remote area it may be all that you can get.

    I read his statement: "I am planing for a hybrid system which includes solar panels as well as the NEA one" to mean: "I am planing for a hybrid system which includes solar panels as well as utility power".
    With only 4 hours per day of 220 by 6 amps, a grid-based battery charger is not going to do him much good, raising the relative value of a solar PV contribution. Here is a case where even if the price of grid power is low, the supply is strictly limited, making the marginal cost of more power beyond that amount effectively infinite. So in that particular case, you would compare the cost of solar to the value of the power produced, in terms of what it is used for, rather than to the cost of utility power.

    An interesting use case!
    SMA SB 3000, old BP panels.
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  • Nawam
    Nawam Registered Users Posts: 5 ✭
    #6
    Re: Help needed to build a Hybrid System

    - Thank you so much for your reply guys.
    And I am sorry I confused some of you with the NEA thing. :p . It is Nepal Electricity Authority, they provide the electricity.
    What is confusing me the most is, Is a hybrid system cost effective than a full powered off grid solar system ??
    I read somewhere that making hybrid systems is actually more expensive than we think it is.
    I'll try to explain you guys about the load use of mine,
    100W television for maybe 4-5 hrs
    5 X 30W lights for 4-5 hrs
    100W computer for 4-5 hrs
    800W Fridge
    So, will a 1kW system work for this ? or will I need a bigger system.
    Also, I am planning for two 12V 150Ah batteries. Would it be better using them in series or parallel connection ? I am really confused in setting up the battery. :D
    And should I be using a 1000VA inverter just because it is a hybrid system??
    The more I think about this the more it gets confusing. :confused:
    Thank You ..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Help needed to build a Hybrid System

    A hybrid system can be more cost effective if the utility will buy back any surplus power you produce. Otherwise it is the same thing as an off-grid system, simply using the grid as a back-up generator.

    A 100 Watt TV for 5 hours = 500 Watt hours.
    5 * 30 Watt lights = 150 * 5 hours = 750 Watt hours.
    100 Watt computer for 5 hours = 500 Watt hours.
    800 Watt refrigerator? More likely <200 Watts * 8 hours or so (they cycle on and off) = roughly 1200 Watt hours.

    Right there you see 2950 Watt hours. That's quite a bit of power. On 12 Volts it would be roughly 275 Amp hours, or at least 550 Amp hour 12 Volt battery.
    The inverter needs to be sized to supply the maximum loads at any given time. The refrigerator will probably demand >1000 Watts to start up, even though it will only draw 120 Watts or so when running.

    The solar panels need to be sized to recharge the batteries. With grid available, that can take some of the recharging duty. How much depends on how dependable the grid is.
    As a rule, that 550 Amp hour 12 Volt bank would have at least 850 Watts of array to recharge with. It would also work better as a 24 Volt system, as that will reduce the current through the wires and simplify the battery bank arrangement.
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  • Nawam
    Nawam Registered Users Posts: 5 ✭
    #8
    Re: Help needed to build a Hybrid System

    Sorry to be so dumb but I am not being able to reason myself in a particular choice for the battery connections.
    I have two 12V 150Ah batteries. Now my load is not more than 1kW per day (I'll just be using few light bulbs, a television and a computer at most).
    Now what is the difference in having a series connection or parallel connection of the batteries ?? For my two batteries I get either a 12V 300Ah battery bank or a 24V 150Ah battery bank. What is confusing me the most is if I opt to go for the 24V system will my power finish quicker than the 12V one ?? Or say will the 12V system take more time to charge than the other??
    Also, if i go for the 24V connection of the batteries should my Solar panels also have a 24V system. I am planning to use two 36V 120W Solar panels. Now if I have a 24V battery system what would be my best option?? or will the 36V just be fine ??
    I hope you guys understand what I am trying to tell here. :P
    Cheers..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Help needed to build a Hybrid System

    Two configurations of the same two 12 Volt 150 Amp hour batteries:

    In parallel for 300 Amp hours @ 12 Volts: 3600 Watt hours total.
    In series for 150 Amp hours @ 24 Volts: 3600 Watt hours total.

    Either way, same amount of total power. The difference is that the 24 Volt system will use less current to achieve the same amount of power (Watts) by using more Voltage. It is slightly more efficient as a result. Also in this example there is less potential for uneven current sharing with the two batteries in series. In parallel, the Amps in/out of the batteries may differ between the two, especially if the resistance in the connections rises or the battery cables are not equal length.

    The panels must have a Vmp that is high enough to charge the batteries. For a 12 Volt system this means they should have a Vmp around 17 to 18. For a 24 Volt system it needs to be double that.
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  • Nawam
    Nawam Registered Users Posts: 5 ✭
    #10
    Re: Help needed to build a Hybrid System

    Thank You so much.
    If we meet someday the beers on me .8)
    I'll inform if I come across any problem ..
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  • Nawam
    Nawam Registered Users Posts: 5 ✭
    #11
    Re: Help needed to build a Hybrid System

    Ok so here's what i am stuck at,
    Suppose for a 1kW load in a day and 24V system using a DOD of 50% and 3 days of autonomy:
    The ampere hours for battery comes around 250 which needs to be doubled, which gives us about 500Ah of batteries required.
    Now, using only 2 12V batteries of 150Ah will never give me such battery banking. Which means I need two parallel connections of 3 batteries in series, i.e 6 batteries. Even this would only give me a 450Ah 24V system. Is this how it is supposed to be or am I missing something here?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #12
    Re: Help needed to build a Hybrid System
    Nawam wrote: »
    Suppose for a 1kW load in a day and 24V system using a DOD of 50% and 3 days of autonomy:

    1000W / 24v = @42Amps
    42Amps x 3 days = 126 Amps
    126 Amps x 2 (for 50% discharge)= 252 Amp Battery bank at 24 volts
    Nawam wrote: »
    Now, using only 2 12V batteries of 150Ah will never give me such battery banking.

    2 x 12 = 150A string at 24 volts
    2 x 150A string = 300A at 24 volts

    Usually like to run strings at voltage rather than parralleled batteries into strings...
    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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