What is the best way to connect 6x 200W solar pv?

Clarkdale44Clarkdale44 Posts: 17Registered Users ✭✭
edited October 2016 in Solar Beginners Corner #1
Hello

My question straightforward as my title...

Series or parallel or both?

Suppose i have got 6x 200W panal... How do i connect them for max power and efficiency?
How do i connect them if panal voltage is 12v or 24v respectively. And explain if you can...


Above is a pwm charge controller..

If i use 24v, do i need to buy 24v battery?
Any help would be appreciated...
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  • PhotowhitPhotowhit Posts: 4,606Solar Expert ✭✭✭✭
    edited October 2016 #2
    The chart you have pictured shows the wattage for the system voltage, yes, 12 or 24 volt battery bank.

    General rule is, for a PWM charge controller, set them up for the system voltage, If the 200 watt panels have a VMP of 17-19 volts, they are designed to charge a 12 volt battery bank, and they should all be in parallel with each other. If you are using the same panels to charge a 24 volt system they should be 2 in series strings and 3 strings of 2 in parallel.

    If they have  VMP of 34-38 volts then the should all be hooked u in parallel to charge a 24 volt battery bank, with a PWM charge controller.

    If they have a VMP of 20-33 volts they are pretty much designed to be used with a MPPT type charge controller, in which case they tend to be most efficient with a VMP closest to 2x the system/battery bank voltage.


    Your question would be more straight forward if you provided the vmp of the solar panel. They come in all 3 of the above ranges!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • Clarkdale44Clarkdale44 Posts: 17Registered Users ✭✭
    edited October 2016 #3
    Photowhit said:
    The chart you have pictured shows the wattage for the system voltage, yes, 12 or 24 volt battery bank.

    General rule is, for a PWM charge controller, set them up for the system voltage, If the 200 watt panels have a VMP of 17-19 volts, they are designed to charge a 12 volt battery bank, and they should all be in parallel with each other. If you are using the same panels to charge a 24 volt system they should be 2 in series strings and 3 strings of 2 in parallel.

    If they have  VMP of 34-38 volts then the should all be hooked u in parallel to charge a 24 volt battery bank, with a PWM charge controller.

    If they have a VMP of 20-33 volts they are pretty much designed to be used with a MPPT type charge controller, in which case they tend to be most efficient with a VMP closest to 2x the system/battery bank voltage.


    Your question would be more straight forward if you provided the vmp of the solar panel. They come in all 3 of the above ranges!
    Sorry i forgot to add solar panal specs...

    suppose i have 12v panal like below...

    Maximum power (W)

    200
    Optimum power voltage (Vmp) 18.0
    Optimum operating current (Imp) 11.12
    Open circuit voltage (Voc) 22.30
    Short circuit current (Isc) 11.89
    Solar cell: 125 x 125 monocrystalline
    Number of cell (pcs) 6 x 12
    Size of module (mm) 1580 x 808 x 35
    Front glass thickness (mm) 3.2
    Temperature coefficient of Isc (%)/°C + 0.1
    Temperature coefficient of Voc (%)/°C - 0.38
    Temperature coefficient of Pm (%)/°C - 0.47
    Temperature coefficient of Im (%)/°C + 0.1
    Temperature coefficient of Vm (%)/°C -0.38
    Temperature range (°C) -40 to +85
    Tolerance wattage (%) +/- 3
    cell efficiency 18.70
    Surface maximum load capacity (Pa) 2400
    Allowable hail load 23m/s, 7.53g
    Frame Anodized Aluminium Alloy
    Weight per piece (kg) 15.5
    Standard test conditions AM1.5, 1000W/m2, 25°C (+/-2°C)
    FF (%) ≥73.3

    or suppose i have 24v panal like below..

    Maximum power (W)

    200
    Optimum power voltage (Vmp) 36.5
    Optimum operating current (Imp) 5.47
    Open circuit voltage (Voc) 44.5
    Short circuit current (Isc) 5.90
    Solar cell: 125 x 125 monocrystalline
    Number of cell (pcs) 6 x 12
    Size of module (mm) 1580 x 808 x 50
    Front glass thickness (mm) 3.2
    Temperature coefficient of Isc (A)/°C +0.065
    Temperature coefficient of Voc (mV)/°C -80
    Temperature coefficient of Pm (%)/°C -0.45
    Temperature coefficient of Im (%)/°C +0.1
    Temperature coefficient of Vm (%)/°C -0.38
    Temperature range (°C) -40 to +85
    Tolerance wattage (%) +/- 3
    Module efficiency (%) 12.20
    Surface maximum load capacity (Pa) 2400
    Allowable hail load 23m/s, 7.53g
    Frame Anodized Aluminium Alloy
    Weight per piece (kg) 15.5
    Standard test conditions AM1.5, 1000W/m2, 25°C (+/-2°C)
    FF (%) ≥73.3


    I tried to make sense of what you said about the panal connection.. i made it's graphical representation
    Sorry for the messy drawing..

    Is this how it should look if used 12v panal...?

    If it is then in future if i need to add more panals.. i just need to buy two 12v panals or single 24v 200W panal and attach them in series and parallel depending on the panal voltage

    The only advantage of 24v system is that i don't need to use thicker wires.. What if i say i won't be using them for dc appliances, instead i will use dc to ac inverter to run my ac loads (off grid)?


    But again with 12v system i can only go max 500W... with 24v i can go up to 1000W.

    I have made another diagram for connection.. please have a look...

    I have connected first five 12v 200w panals in parallel and last one in series.. This one gives me 1000W 24v... Is this a correct way?

     

    Also i was thinking of aligning them like this



    2x facing east-south
    2x in the south
    and 2x in the south-west for decent power throughout the day... is that a good thing to do? or should i just align all them facing south?

    I thought of this because sun rays in the morning say 8 am or 9 am won't be falling straight on the panals... If few of the panals were facing east side then they would be able to generate more power than the panals facing south during that time... same goes for the south-west facing panals, Don't you think so?
  • BB.BB. Posts: 27,575Super Moderators admin
    Forget your 5 series + 1 series setup... It will not give you very effective output power... More or less, it would be roughly equivalent to 1+1 in series. 4 of the panels are completely wasted.

    When placing panels in series--Your want each panel to have the same Imp (current maximum power rating). If panel A outputs 5 amps, then the series connected panel B would also be rated at 5 amps. If you had a 25 amps 5 panels parallel in series with a 5 amp panel, then the 5 amp panel will limit the total current through the string.

    So in your example with 2series * 3 parallel strings... That would be very nice for your SE/South/SW facing array. We call it "virtual tracking". Lead Acid batteries really "like" getting charged for many hours per day--I.e. charging 7% rate of charge for 10 hours per day is better than charging at 14% for 3.5 hours per day. Your total power per day is less from a virtual tracker vs all panels facing south, but it is (many times) cheaper to have a larger virtual tracker than to go to the expense of a smaller array + physical tracker (hardware, motorized actuator, controller, large steel pole, large concrete base).

    More or less, it usually works out that PWM works cost effectively for smaller systems of 400 Watts or less. And MPPT work out for systems with 800 Watt or larger arrays. Note with PWM controllers you need "24 volt array" (really Vmp-array~36 volts) and a 24 volt batttery bank (or 12/12, 48/48 volt)... An MPPT type charge controller lets you work with Vmp-array that is >> battery bank voltage so you can put the array a longer way (100's of feet) from the battery shed (high voltage array/low current--MPPT controller "efficiently down converts" to low voltage/high current needed to charge the battery bank).

    Rather than get too bogged down in "what ifs" and generic system design rules--Do you have an idea of what loads you want to support (maximum Watts, Watt*Hours per day, time of day of power usage (night or day)). Where the system will be installed (nearest major city)? Full time off grid or weekend/summer use?

    It is less confusing to design to your needs, vs talking about general design principles. Many times, the solutions end up being different (1,000 WH per day 12 volt system vs 3,300 WH per day and 24 or 48 volt system that has an electric refrigerator and a deep well pump).

    Once you know your loads--We can then help you with a couple of paper designs to see what works best for your needs (12/24/48 volt, PWM or MPPT controller, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Clarkdale44Clarkdale44 Posts: 17Registered Users ✭✭
    BB. said:
    Forget your 5 series + 1 series setup... It will not give you very effective output power... More or less, it would be roughly equivalent to 1+1 in series. 4 of the panels are completely wasted.

    When placing panels in series--Your want each panel to have the same Imp (current maximum power rating). If panel A outputs 5 amps, then the series connected panel B would also be rated at 5 amps. If you had a 25 amps 5 panels parallel in series with a 5 amp panel, then the 5 amp panel will limit the total current through the string.

    So in your example with 2series * 3 parallel strings... That would be very nice for your SE/South/SW facing array. We call it "virtual tracking". Lead Acid batteries really "like" getting charged for many hours per day--I.e. charging 7% rate of charge for 10 hours per day is better than charging at 14% for 3.5 hours per day. Your total power per day is less from a virtual tracker vs all panels facing south, but it is (many times) cheaper to have a larger virtual tracker than to go to the expense of a smaller array + physical tracker (hardware, motorized actuator, controller, large steel pole, large concrete base).

    More or less, it usually works out that PWM works cost effectively for smaller systems of 400 Watts or less. And MPPT work out for systems with 800 Watt or larger arrays. Note with PWM controllers you need "24 volt array" (really Vmp-array~36 volts) and a 24 volt batttery bank (or 12/12, 48/48 volt)... An MPPT type charge controller lets you work with Vmp-array that is >> battery bank voltage so you can put the array a longer way (100's of feet) from the battery shed (high voltage array/low current--MPPT controller "efficiently down converts" to low voltage/high current needed to charge the battery bank).

    Rather than get too bogged down in "what ifs" and generic system design rules--Do you have an idea of what loads you want to support (maximum Watts, Watt*Hours per day, time of day of power usage (night or day)). Where the system will be installed (nearest major city)? Full time off grid or weekend/summer use?

    It is less confusing to design to your needs, vs talking about general design principles. Many times, the solutions end up being different (1,000 WH per day 12 volt system vs 3,300 WH per day and 24 or 48 volt system that has an electric refrigerator and a deep well pump).

    Once you know your loads--We can then help you with a couple of paper designs to see what works best for your needs (12/24/48 volt, PWM or MPPT controller, etc.).

    -Bill
    Well... you pretty much solved every doubt i had about solar...

    I can indeed take professional help for installation .. but in my area they are only installing large grid tie inverters (3 to 10kva)... which i can't afford at the moment..

    I want a small off grid system at home (max 600w) so i could use it with my dc - ac inverter for running my electrical loads during day time. And at night if there is a power cut...

    Anyway, thank you for your reply... it was very helpful...
  • BB.BB. Posts: 27,575Super Moderators admin
    600 Watt--Is that a 600 Watt inverter or a 600 Watt solar array? What is the DC bus voltage for your AC inverter?

    Generally, if we are starting with loads, a 500 Watt*Hour per day system (roughly 250 Watt of solar panel(s)) is enough to run a laptop a few hours per day, cell phone charger, LED lighting, small LED TV, etc.

    A 1,000 WH per day system--More laptop usage, RV Water pump from cistern--Pretty much a "comfortable" amount of power--Excluding a refrigerator.

    Add a Honda eu2000i (1,600 watt genset) for bad weather/running a larger load (saw, recharging battery bank during bad weather) plus 10-20 gallons of gasoline with fuel stabilizer (change out fuel every 6-12 months) and you are set for 5-10 days of emergency backup power (and enough to run the refrigerator 12 hours per day--even if your solar system is too small).

    A 3,300 WH per day system--Pretty much an almost normal "electrical life" in a very conservation minded home (refrigerator, add deep well pump, clothes washer, etc.).

    Of course--All of this is dependent on your energy needs (power usage is a highly personal set of choices--What works for me, may not for you).

    1,000 WH per day or less--A "small" solar power system.

    3.3 kWH per day--You are in the middle of solar power--The refrigerator really pushes the solar power system larger.

    Note--There are choices here too... An Energy Star rated full size fridge can be very cheap to buy and maintain--But you need a good size solar power system to power. A DC refrigerator may be 1/2 the cubic foot storage and 3x as expensive--But you can get away with around 1,000 WH per day system.

    Similar if you have a well pump... A "cheap" induction motor 240 VAC well pump (1.5 HP)--Need a good size solar system to manage the starting surge current. Get a "solar friendly" well pump for a lot more money, but almost no surge current--And some (of the more expensive models) will run directly from solar panels (pump when the sun is up) or even from a 48 VDC battery bank.

    Lots of options and choices... I suggest that you try several paper design (paper is cheap and easy to change)--And see what best meets your needs--And, if you are interested in saving money--Conservation is your first choice. Insulation, Energy Star appliances, LED lighting, etc. is almost always cheaper than building out an off grid power system to power them.

    Grid Tied Solar--It is getting towards the end of its government subsidies (in my humble opinion). Today (or at least yesterday)--A GT system could drop your electric bill to $5 per month.

    In the future (next few years to next decade)--A GT power system may only be able to knock 1/4 to 1/3 off of your power bill (for many reasons--This is what makes "economic sense" to utilities and customers at large). And going off grid--It is not unusual for that power to cost your $1 to $2+ per kWH or almost 10x your utility power costs--So, again, conservation is critical here. I do not want to "spite" my utility by driving my electrical costs up by a factor of 10x.

    A great little tool to understand your power needs is a Kill-a-Watt type power meter. Just plug your loads in (one at a time, 120 VAC max 15 amps) and see where you are spending your money (and where conservation makes the most sense). With the meter and a bit of math (spread sheet)--It really brings home how cheap power power is today.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Clarkdale44Clarkdale44 Posts: 17Registered Users ✭✭
    edited October 2016 #7
    BB. said:
    600 Watt--Is that a 600 Watt inverter or a 600 Watt solar array? What is the DC bus voltage for your AC inverter?

    Generally, if we are starting with loads, a 500 Watt*Hour per day system (roughly 250 Watt of solar panel(s)) is enough to run a laptop a few hours per day, cell phone charger, LED lighting, small LED TV, etc.

    A 1,000 WH per day system--More laptop usage, RV Water pump from cistern--Pretty much a "comfortable" amount of power--Excluding a refrigerator.

    Add a Honda eu2000i (1,600 watt genset) for bad weather/running a larger load (saw, recharging battery bank during bad weather) plus 10-20 gallons of gasoline with fuel stabilizer (change out fuel every 6-12 months) and you are set for 5-10 days of emergency backup power (and enough to run the refrigerator 12 hours per day--even if your solar system is too small).

    A 3,300 WH per day system--Pretty much an almost normal "electrical life" in a very conservation minded home (refrigerator, add deep well pump, clothes washer, etc.).

    Of course--All of this is dependent on your energy needs (power usage is a highly personal set of choices--What works for me, may not for you).

    1,000 WH per day or less--A "small" solar power system.

    3.3 kWH per day--You are in the middle of solar power--The refrigerator really pushes the solar power system larger.

    Note--There are choices here too... An Energy Star rated full size fridge can be very cheap to buy and maintain--But you need a good size solar power system to power. A DC refrigerator may be 1/2 the cubic foot storage and 3x as expensive--But you can get away with around 1,000 WH per day system.

    Similar if you have a well pump... A "cheap" induction motor 240 VAC well pump (1.5 HP)--Need a good size solar system to manage the starting surge current. Get a "solar friendly" well pump for a lot more money, but almost no surge current--And some (of the more expensive models) will run directly from solar panels (pump when the sun is up) or even from a 48 VDC battery bank.

    Lots of options and choices... I suggest that you try several paper design (paper is cheap and easy to change)--And see what best meets your needs--And, if you are interested in saving money--Conservation is your first choice. Insulation, Energy Star appliances, LED lighting, etc. is almost always cheaper than building out an off grid power system to power them.

    Grid Tied Solar--It is getting towards the end of its government subsidies (in my humble opinion). Today (or at least yesterday)--A GT system could drop your electric bill to $5 per month.

    In the future (next few years to next decade)--A GT power system may only be able to knock 1/4 to 1/3 off of your power bill (for many reasons--This is what makes "economic sense" to utilities and customers at large). And going off grid--It is not unusual for that power to cost your $1 to $2+ per kWH or almost 10x your utility power costs--So, again, conservation is critical here. I do not want to "spite" my utility by driving my electrical costs up by a factor of 10x.

    A great little tool to understand your power needs is a Kill-a-Watt type power meter. Just plug your loads in (one at a time, 120 VAC max 15 amps) and see where you are spending your money (and where conservation makes the most sense). With the meter and a bit of math (spread sheet)--It really brings home how cheap power power is today.

    -Bill
    Again thanks for this immense reply...

    I forgot to mention few things...

    600Wp solar array and 1000W 12v inverter

    I will not be running heavy loads like refrigerator or motor.

    The only things i will be running is few fans, led lights and TV.

    As i said earlier i want off grid system to run the above loads during day time and at nights if there is power cut.
    In future i may install grid tie but not for now...

    i will be running 100 to 300w average loads daily during the day on solar.

    My fan uses about 70w on full speed = 3 fans
    my leds are rated 10w = 5 leds
    TV is 30w = 2

    You may work out the estimate load. The above loads doesn't mean i will be running all at once...


    During the day i will use solar power to run my load + it will also charge batteries and at night load will run on mains power and if there is a power cut then it will run on batteries.


  • BB.BB. Posts: 27,575Super Moderators admin
    One part missing--How many hours per day do you want to run each load (5 hours fans, 5 hours LED, 6 hours TV, etc.)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Clarkdale44Clarkdale44 Posts: 17Registered Users ✭✭
    edited October 2016 #9
    BB. said:
    One part missing--How many hours per day do you want to run each load (5 hours fans, 5 hours LED, 6 hours TV, etc.)?

    -Bill
    5-6 hours daily... on average basis..
    I won't be running all the load at the same time...
  • BB.BB. Posts: 27,575Super Moderators admin
    My fan uses about 70w on full speed = 3 fans
    my leds are rated 10w = 5 leds
    TV is 30w = 2
    6 hours per day:
    • 70w * 3 fans * 6 hours = 1,260 WattHours per day
    • 10 watts * 5 LEDs * 6 hours = 300 WH per day
    • 30 Watt * 2 TVs * 6 hours = 360 WH per day
    • 1,920 WH per day total
    Note that the fans are a pretty significant load... There are smaller/more efficient fans that folks use in RV, or some ceiling fans, etc.... But what you started with:
    • 1,920 WH per day * 1/0.85 AC inverter eff  * 1/12 volt battery bank * 2 days storage * 0.50 max discharge (for longer battery life) = 752 AH @ 12 volt battery bank
    • 1,920 WH per day * 1/0.85 AC inverter eff  * 1/24 volt battery bank * 2 days storage * 0.50 max discharge (for longer battery life) = 376 AH @ 24 volt battery bank
    You can get away with a 12 volt battery bank--But I would highly suggest that you look at a 24 volt battery bank minimum. More or less, for various reasons, when you get over an 800 AH battery bank, you should look at the next higher battery bus voltage. (this is the same "amount" of batteries--Just different series/parallel arrangement--Or different/AH capacity cells).

    If you started with golf cart batteries, that would be 4 x 6 volt @ ~200 AH times 2 parallel strings for a 24 volt @ 400 AH battery bank (golf cart batteries are cheap and pretty rugged deep cycle batteries. And most people kill their first one or two banks of batteries).

    To charge such a bank, you would need 5% to 13% or so rate of charge. 10%+ for a full time off grid system is highly recommended for longer battery life/less fussing around with managing loads during cloudy weather, etc.
    • 400 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 753 Watt array minimum (weekend/summer season usage)
    • 400 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,507 Watt array nominal (full time off grid)
    • 400 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,958 Watt array "cost effective" maximum
    And then based on where you live, hours of sun (guessing):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Delhi
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 61° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    5.17
     
    5.91
     
    6.48
     
    6.20
     
    5.89
     
    5.42
     
    Jul Aug Sep Oct Nov Dec
    4.76
     
    4.61
     
    5.28
     
    5.81
     
    5.56
     
    4.96
     
    August is the minimum month, but still quite a bit of sun at 4.61 hours of sun long term average (note--these are average values. You can have a week of bad weather with only 5%-10% of predicted average output (worst case)--So you have the choice of using genset or AC mains to make up power, or simply not use some loads until the sun returns).
    • 1,920 Watt*Hours per day load * 1/0.52 typical off grid AC system eff * 1/4.61 hours of sun (August) = 801 Watt array minimum (break even for August)
    So, somewhere between 801 and 1,507 Watt array (minimum to nominal) to 1,958 Watt array cost effective maximum.

    For a system this large, is around a 60 Amp PWM controller or MPPT charge controller (minimum) for a 1,950 Watt array... In general, would suggest a MPPT type charge controller, but if the solar array is close to the charge controller+battery bank, a PWM controller could work (depending on solar panels and their configuration).

    A Vmp-array ~ 36 volts for PWM controller, and minimum voltage for MPPT. The high voltage array would be Vmp-array ~ 100 VDC vor a 140-150 VDC max input MPPT controller with Vmp-array ~ 72 volts probably being the "optimum" for a 24 volt with MPPT charge controller.

    These days, batteries tend to be expensive and solar arrays are cheap. For longer battery life and less fussing over loads on cloudy days, and daytime vs night time loads, having more solar panels is usually a nice solution. And remember that Lead Acid (and many other chemistry) batteries do not like to be taken "dead"--Do that and your bank will not be long for this world. Assume that "cheap" golf cart batteries will last 3-5 years, and more expensive batteries around 5-8 years (fork lift batteries can last 15+ years).

    Also assuming you are in a warm to hot climate, batteries do last as long if kept hot... A good rule of thumb is for every 10C over 25C cuts the battery aging life by 1/2.

    Anyway--Some estimates based on your loads and my guess at where you are located.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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