expanding from inherited panels

nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
ok, so I have recently come into 5 sharp nd-130 ujf panels (12v by sharps online description, though the back of the panels say 21v?)...anyways, Im close to needing to put together a system for my house in the western hills of Maine (elv ~ 1000'), and need a system to run a shallow well pump which draws no more than 25 verticle feet and 20' from well to input at house. Also wish to run a chest fridge, misc high efficiency electronics such as led tv, led lighting, occasional charging of my 18v dewalt tool batteries, cell phones, radio...things like that. perhaps a fan or two. No heavy draw motors (aside from fridge compressor and pump), no elements, microwaves, dryers, etc.

I am thinking a bank of crown l-16s wired for 24v, maybe eight at most. I have 4-6k to spend to outfit this system. Would a good way to get a 24v bank derive from 8 390ah 6v batteries? Is this overkill for what I wish to run? Going off the assumption its not, for the time being, considering I have those 650 watts of sharp panels, how much more should I need to create a balanced system? Is it allright to use higher voltage, bigger panels alongside the sharps if I went with a 45 or 60 amp mppt controller such as the morning star or outback to handle the panels? Lastly, would it be prudent to use something like an outback vfx charger/inverter or the like for such a system, or is that overkill? I certainly dont want a cheap inverter, as every load will be 120ac. Any quality inverter/chargers come to mind that might be more apporopriate (and cost effective) for this system?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: expanding from inherited panels

    Brakes on, back the truck up.

    First, what you've got: five 130 Watt 12 Volt nominal panels. The 21 Volts would be Voc and the Vmp is probably about 17.5. Imp is probably about 7.4. Perfectly normal and usable panels. Unfortunately there are five which limits configuration somewhat unless you lose one or add one.

    Second, whereas a 24 Volt system is desirable see the limitation in array configuration above. It would be worthwhile making a change or two to accommodate 24 Volts. Let's say you use four of the panels: you'd have 520 Watts and about 17 Amps peak current. That is not going to charge any L16's; it's just too low. It certainly isn't going to do two strings of 390's (780 Amp hours).

    Which brings us to third; you're guessing at loads. The only thing that is good for is being disappointed with the results. Get a Kill-A-Watt and pretend you're running what you would from solar. Measure everything you'd use under typical conditions and get a good basis for Watt hour consumption. It's a pain, but worth it in the end.

    The array is going to come up small for what you want. You could probably add in another 130 Watt panel from another maker like this one http://www.solar-electric.com/solartech-spm130p-s-n-130-watt-multicrystalline-solar-module.html/ which would give you 780 Watts. That's enough to start with. I use a slightly smaller array on 232 Amp hours @ 24 Volts and it works well when the sun shines and loads are managed. You could use this on a Kid and get 25 Amps on a 24 Volt system.

    To increase the power further I'd recommend a different array on a different controller. The reason being it is difficult to find true 24 Volt panels these days and the true 12 Volt ones are expensive per Watt. So going with GT style panels and another Kid controller will be the most power for the least headache. You could double up the array size and run a bank of two battery strings in parallel around 440 to 464 Amp hours without difficulty. Then you'd be around 2.5 kW hours of power at 25% DOD.

    But get some real consumption numbers first. You'll be glad you did.
  • BB.BB. Super Moderators, Administrators Posts: 30,177 admin
    Re: expanding from inherited panels

    Also--Question about the well... ~25' is just about the theoretical maximum for any pump to "lift water" at sea level (~20' lift is probably a day to day operational minimum at sea level). Any problems (small air leak in lift pipe, bad foot valve, pump wear, clogged input filter/screen, etc.) and you will be fighting loss of prime/unreliable pump operation.

    I would seriously look at converting to a submerged pump or how to get the lift distance down (or look at those "terrible" for off grid systems, very inefficient jet pumps).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: expanding from inherited panels

    At this point, it is not possible to gauge loads...I do not have any of the equipment which will be going into the house. The main concern is the well pump and lights (everthing else is a bonus but non-essential to me), which I am certainly going with submersible, and the well is being dug this week comming. The guy digging the well has dowsed the site, and expects water at eight foot down on a very strong vein. hes dowsed and dug two other wells on our 51 acres, with uncanny accuracy...so while I dont know the precise figures until the deed is done, Im trying to project the general expense a little ahaed of time.

    So, 'coot, not sure if im understanding you correctly, but are you suggesting running two strings of panels through two seperate charge controlllers into the same bank which is half the size I was proposing? One being six 130ws, and the other being higher wattage GT panels? Also, whats a kid controller, and can you give me an example of one which would suit the system? Thanks for the replies from the both of you, the alacrity of this forum amazes.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: expanding from inherited panels
    First, what you've got: five 130 Watt 12 Volt nominal panels. The 21 Volts would be Voc and the Vmp is probably about 17.5. Imp is probably about 7.4. Perfectly normal and usable panels. Unfortunately there are five which limits configuration somewhat unless you lose one or add one.

    Minor point... He could use the 5 panels in series... Voc would be a bit over 100 volts, manageable (even in Maine) on a 150 volt Vmax controller.

    But that said, I totally agree that he needs to come up with a kwhr per day number to design the system around. And he will need a larger array than 650 watts. He might be better off spending his money on some GT panels, rather than another 12 volt panel.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 30,177 admin
    Re: expanding from inherited panels

    The design... Either you have loads in mind, or we design a system around some key component (solar panels or batteries you already have and "must use").

    5x 130 Watt panels = 650 Watt system.

    We suggest a battery bank with 5% to 13% rate of charge from solar as "workable/ideal":

    650 Watts * 0.77 panel+controller derating * 1/0.05 rate of charge * 1/14.5 volt charging = 690 AH @ 12 volt battery bank (weekend/light use)
    650 Watts * 0.77 panel+controller derating * 1/0.10 rate of charge * 1/14.5 volt charging = 345 AH @ 12 volt battery bank (daily use)
    650 Watts * 0.77 panel+controller derating * 1/0.13 rate of charge * 1/14.5 volt charging = 266 AH @ 12 volt battery bank (heavy daily use)

    All of those would work fine with a 12 volt battery bank (690 AH is getting pretty big for a 12 volt bank).

    You live in Main, using Solarelectrichandbook for Ahgusta Main, 45 degree panel angle (fixed):

    [h=3]Augusta
    Average Solar Insolation figures[/h] Measured in kWh/m2/day onto a solar panel set at a 46° angle:
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    3.28

    4.07

    4.63

    4.59

    4.50

    4.64



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    4.69

    4.80

    4.39

    3.60

    2.68

    2.58



    Toss the bottom 3 months, and the minimum (long term average) sun is ~3.60 hours per day (October). A 650 Watt array:

    650 Watt array * 0.52 system eff * 3.6 hours of sun = 2,340 Watt*Hours per day minimum for ~9 months of the year

    If you have heavy snows--You might think about an array you can adjust between winter (near vertical to shed snow) and optimal angle for summer (more power). You do not appear to get "lots of sun" -- So even adjust angles is not going to make a huge difference. Run the numbers and see what works for you.

    More or less--I would suggest a 3.3 kWH per day system if you are going to run an energy star refrigerator... Otherwise, your system should be more than enough to keep you in power (other than deep winter possibly) for lights, water, laptop computer, low power LCD TV, battery chargers, etc.

    However--Watch the loads that may run many hours per day--For example, fans can actually be a significant load on your system. There are some low power DC fans that folks have used and are very happy.

    A Kill-a-Watt type meter for AC loads--A DC clamp meter or DC AH/WH meter can be very handy for estimating/measuring DC loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: expanding from inherited panels
    vtmaps wrote: »
    Minor point... He could use the 5 panels in series... Voc would be a bit over 100 volts, manageable (even in Maine) on a 150 volt Vmax controller.

    But that said, I totally agree that he needs to come up with a kwhr per day number to design the system around. And he will need a larger array than 650 watts. He might be better off spending his money on some GT panels, rather than another 12 volt panel.

    --vtMaps

    I would not want to run five in series with a Voc of 21: 105 total, with a possibility of getting close to shutdown on a Winter's day in deep and dark December. Or January. Also the Vmp at 87.5 would be rather high for a 24 Volt system, affecting efficiency. Adding one Solar Tech panel solves the trouble and gives another 130 Watts.

    To the OP: the Kid is a 30 Amp MPPT controller from MidNite Solar; http://www.solar-electric.com/midnite-solar-kid-mppt-charge-controller.html

    Using one of these with the existing panels and another with an array of different panels will solve the configuration problems. The two identical controllers can co-ordinate with each other.
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: expanding from inherited panels

    "We suggest a battery bank with 5% to 13% rate of charge from solar as "workable/ideal":

    650 Watts * 0.77 panel+controller derating * 1/0.05 rate of charge * 1/14.5 volt charging = 690 AH @ 12 volt battery bank (weekend/light use)
    650 Watts * 0.77 panel+controller derating * 1/0.10 rate of charge * 1/14.5 volt charging = 345 AH @ 12 volt battery bank (daily use)
    650 Watts * 0.77 panel+controller derating * 1/0.13 rate of charge * 1/14.5 volt charging = 266 AH @ 12 volt battery bank (heavy daily use)

    All of those would work fine with a 12 volt battery bank (690 AH is getting pretty big for a 12 volt bank)." -Bill

    Hi Bill...Question; Was this put in the correct order? You have the bigger bank designated under the lightest level of use...is this correct or did you mean that the 690ah bank is recommended for heavy use?

    Also, to achieve the 3.3kw range (using the same formulae in reverse), I would need another 130w panel to fill out the 12v string, and then around 1k of GT panels for the second string (using a pair of those kid controllers that Coot recommended)?

    Assuming I went with such a configuration, and wanted to have a 24v bank, what would make for a nice balanced battery bank? Is there a reason I should go with a 12v bank as you listed over a 24v configuration?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: expanding from inherited panels

    Let's look at it with a little more focus.

    IF you had six 130 Watt panels you'd have 780 Watts of array. From that you could expect a peak charge current of about (780 * 0.77 /24) 25 Amps which would be 10% of 250 Amp hours. That would provide at 25% DOD approximately 1.5 kW hours. So if you doubled both the array and battery bank you'd have about 3kW hours capacity at 25% DOD.

    Here come the caveats!
    Battery banks don't come in any size you want, so you need to make allowances. That 25 Amps would be good for: a set of GC2's (220 Amp hours), a set of T105's (225 Amp hours), a set of PS2200's (232 Amp hours) et cetera up to whatever you can find that might be 250 Amp hours or a little bit more. This is that range of charging, and by the way forget about 5% because that really only works with no-load charging (concurrent loads reduce the effective charge rate).
    How much power you get in Watt hours AC is another matter, as it depends not only on the particular inverter's power consumption and conversion efficiency but also on how you use the power; being able to run opportunity loads when the batteries are at/near full charge will greatly improve the over-all efficiency of the system. Otherwise you are calculating for all power stored in and used from batteries and that can be a dreadful loss. Usually in those circumstances the end-to-end efficiency is 52%, so the 780 Watt array in 4 hours of equivalent good sun gives (780 * 4 * 0.52) 1.6 kW hours. Numbers are never carved in stone.

    A 12 Volt system is to be avoided unless it is absolutely necessary. 24 Volts is a major improvement in efficiency without the added costs of increasing to 48 Volts.
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: expanding from inherited panels

    would a "set" of batteries be defined as a pair? This would mean that if I doubled the array, I could use four 12v T-105s wired in 24v for 550ahs? Sorry for questions that might seem repetitive as I try to grasp the info. To further illustrate my power needs, most water usage would be in the daylight hours, but the lady of the house takes showers at night, so Ive factored in Yamaha ef2000is to run heavier loads at night and to charge batteries. Also have a 5500w genset allready, if need be. But for the most part, nightime loads would be small load electronics like led tv and led lights.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: expanding from inherited panels
    would a "set" of batteries be defined as a pair? This would mean that if I doubled the array, I could use four 12v T-105s wired in 24v for 550ahs? Sorry for questions that might seem repetitive as I try to grasp the info. To further illustrate my power needs, most water usage would be in the daylight hours, but the lady of the house takes showers at night, so Ive factored in Yamaha ef2000is to run heavier loads at night and to charge batteries. Also have a 5500w genset allready, if need be. But for the most part, nightime loads would be small load electronics like led tv and led lights.

    A set of batteries in this case is the number needed to make the Voltage. All those models I quoted are 6 Volt, so a set is four. Four T105's adds up to 225 Amp hours @ 24 Volts. Eight would be required (two parallel strings of four in series) to achieve 450 Amp hours @ 24 Volts.

    Having back-up power is always a good idea. The Yamaha gens have a good reputation too. Also, you may be able to adjust your nighttime water use by increasing the capacity of your pressure tank(s) so that they can store up water (under pressure) during the day when PV power is available for pumping.

    You'd be amazed at how much those 'small loads' add up to in Watt hours. 125 Watt TV for two hours = 250 Watt hours. Not including DVD player or cable box or whatever. My satellite Internet connection system would use as much in a day as the refrigerator does if I didn't shut it off at night.
  • BB.BB. Super Moderators, Administrators Posts: 30,177 admin
    Re: expanding from inherited panels

    Sorry for the confusion... I really like to know the loads and design the system to support the loads--Then the design progression makes a bit more sense the first time.

    When you start somewhere else (like with XYZ watts of solar panels), I am fitting the rest of the system to match the amount of solar panels you have.

    The batteries are really the "heart" of the system. Batteries do not "create" or generate power, they just store what is fed them, and then output it to your loads.

    Batteries have a set of characteristics that they need to follow so that they will have a a long and productive life.

    One of the first is how much current they receive when charging. Too low of rate (less than ~5%), the batteries will not chemically charge correctly and will take a very long time to reach full charge (both are very hard on the plates--Sulfation, poor mixing of electrolyte, the pores in the plates become plugged up, etc.)--All of this can cut years off the life of the battery bank.

    Next, batteries can only output so much current... The faster you discharge them (higher current draw), the less efficient they are (more energy is turned into heat). And if you draw too much current, their output voltage would simply collapse (for example, a small motorcycle battery cannot start a car engine reliably).

    Lastly, you need to refill the battery bank with energy from the solar array. A If you only use the system during a weekend, your battery bank can refill the next day or so just fine. If you use it every day, then you really need to refill the battery bank every day (via solar, grid power, generator, etc.).

    So, for a weekend cabin, you can have a larger battery bank with XYZ panels. It will start/run larger loads (well pump, over night power, etc.).

    For daily power use--A smaller battery bank will recharge faster/more fully every day--And you can use power during the day (computer, TV, etc.). So, you have enough power to both properly recharge the bank when you also run your day time loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: expanding from inherited panels

    ah, thank you so much, 'coot. I feel like im getting somewhere now. So running a string of those 6 130w, and a string of say 4 250w GTs...each on one of those kid controllers, and into a bank of eight T-105s into something like an outback vfx3524...is this viable? So far as the small loads, a 20-30" led, a solid state hard drive media player, 2-3 led lights is about my anticipated nightime loads. I was hoping for one of those converted chest fridges as well, but if the system cant handle it, I can just go total luddite mode and use an icebox (as we have an icehouse on premises allready and no lack of winter ice available for year round storage...my brother does this allready).
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: expanding from inherited panels

    It is certainly viable.
    I have 700 Watts on 232 Amp hours @ 24 Volts using a VFX3524. It runs the full size refrigerator, the satellite Internet connection (modem, router, phone adapter, wireless phones), the computers (laptop & netbook), the lights, the water pump, the septic pump, and the occasional microwave zap. A lot of that is possible by managing load times. Some is facilitated by the slight efficiency advantage of high elevation.

    Right now the generator is running everything because it won't stop raining! Today the rain is even knocking out my sat connection repeatedly! ARGH! :grr

    Your plan for about double the battery bank and array would be good for all that you want I should think. Four 250 Watt panels would be slightly over the Kid's 30 Amp limit, but not that it would do any harm. You'd get about 32 Amps potential. So 30 Amps there and 25 from the other array and you've got 55 Amps of peak current at 24 Volts. More than enough for 450 Amp hours @ 24 Volts. That would be about 2kW hours AC at 25% DOD on batteries alone. Here's a hint; I can squeeze about 500 Watt hours more than that out of my system; being able to make use of good sun when the batteries are near/at full charge can really improve the total output.

    As it is I'm adding more panels to my system to catch the morning sun and start charging earlier. If the sun ever shines again and I can actually put them up.

    P.S.: As I wrote this the net went down twice from the rain. Now wait for it to come back so I can send it.
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: expanding from inherited panels

    Thanks for clearing that up for me, Bill. This is a full time off grid house, and Im comming from the angle of "I've got these 5 panels and between 4-6 thoudand to spend on power, my main concerns being water pumping and lights". As long as I can do that, I can work around the rest to most effectivly use my system, wether that means adding a few loads to get a good dischage rate or being bare bones with water/lights.
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