New to Solar - Need help figuring out what I really need

Musterpoint
Musterpoint Registered Users Posts: 6
Hi Folks,
Great forum, I'm completely new to solar and have a lot to learn, but need to set something up on my boat. There's a great deal of youtube videos showing lots of products and technical blurb but few show product combinations that work well with each other for my particular requirement. That's is what I'm missing.

A bit of background: I need a long range cruising system for a sailboat. It presently has no charging abilities other than engine alternator (12V/80Ah). I intend to add Solar and Wind so I can get by with minimal engine time.

There are 4 batteries on-board: 3 x 12v house batteries provide 330Ah and one 80Ah engine. It has a 110v/12v shore power inverter/charger which will rarely get used.

Assuming I went with 4 x 260w 30A solar panels, my questions are:

Which model charge controller should I get (I believe MPPT is best but make/model?)
Do I need more than one? (I'm having trouble finding 30A, 1040w MPPT)
Can I use the same controller for the wind generator?
Any suggestions or examples greatly appreciated.

Thanks

Comments

  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    Re: New to Solar - Need help figuring out what I really need

    I'm new here myself, but seems like too much panel for that size house battery bank. From what I've read so far here on this forum, I would expect around 600 watts for a nominal 12-volt bank of that capacity. (ETA: For that size panel, you will want to use an MPPT controller, as the Vmp of a 260-watt panel ought to be around 32 volts. A MorningStar TriStar 60 controller ought to work for a 600-watt PV array, with some room for growth if needed.)

    Of course, the first question is:

    What loads do you need to run with this system?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: New to Solar - Need help figuring out what I really need

    One of the big problem with boats and solar is the orientation of panels and shading by lines/masts/sails. Another issue can be dropping of tools/metal line ends/etc. on fragile glass panels. And I would not suggest the flexible/plastic based panels--They probably only last a few years in a marine environment.

    The size of solar array (if you can fit it on the ship) is not bad for your battery bank (5% to ~13% rate of charge based an Battery Bank 20 hour discharge capacity rating--go towards 10%+ for off grid daily use, go down to ~5% for weekend use--if cost/size of array is an issue).

    From what we have seen here, it is not uncommon to find sailors cannot fit enough panels on a boat and run the gear during a race from SF to Hawaii in typical weather without running the batteries dead.

    So, as asked above--What is your daily load plan (Amp*Hours at 12 volts, Watt*Hours, etc.)? Both "desired" and minimum loads.

    Conservation will be your friend, and a good plan for efficient charging of the batteries when needed (will this be your boat motor+alternator, or a small Honda eu1000i or eu2000i type genset or marine equivalent--not sure). Fuel availability (boat motor diesel?) and what you can get in port/amount of fuel storage/etc.... Worst case planning can get very depressing. :cry:

    If most of your loads are purely optional (a few LED Nav lights, Battery powered GPS, few LED cabin/map lights, etc.)--Then your power needs are usually quite manageable.

    Regarding wind (or even towable) turbines. Have you found anybody happy with such units in your circle of friends? In general, turbines are only as reliable as the wind (water turbines only work under way), and can be noisy/a bit of a hazard to be around. But if you need all the power you can harvest, may be the best of a bad situation....

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: New to Solar - Need help figuring out what I really need
    Assuming I went with 4 x 260w 30A solar panels, my questions are:

    Which model charge controller should I get (I believe MPPT is best but make/model?)
    Do I need more than one? (I'm having trouble finding 30A, 1040w MPPT)

    Welcome to the forum,

    I presume (correct me if I'm wrong) that your panels are Vmp about 35 volts and Imp about 7.5 amps, and that the 30 amps you refer to is the combined current of the 4 panels in parallel.

    Charge controllers are rated in amps at their output. Thus if you are charging a battery that is at 12 volts, a controller would need to be rated 86.6 amps to deliver 1040 watts to a 12 volt battery (12 volts X 86.6 amps = 1040 watts). You will rarely get 1040 watts from your panels, so a controller rated 60 amps will be OK. Now, that said, 60 amps into a 330 ah battery bank is pretty high, but most full featured controllers can be set to not exceed a value that you can set... about 45 amps would be right for your batteries.

    btw, the same controller that can push 60 amps into a 12 volt battery (720 watts) can also push 60 amps into a 24 volt battery (1440 watts)... the advantage of higher volts.

    Next consideration is the environment... you need something that can handle a marine environment. Outback makes an "extreme" line of controllers. The new "kid" controller by Midnite also comes in a marine version, but is only rated 30 amps... you would need two of them. That may actually be a good idea... if your panels have different orientations or different shadows there would be an advantage to splitting your panels up into two controllers.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New to Solar - Need help figuring out what I really need

    What I see:

    Three 12 Volt 110 Amp hour batteries in parallel. First thing: check the parallel wiring to be sure they are not 'laddered'. Smart Gauge diagrams: http://www.smartgauge.co.uk/batt_con.html Method #3 should be used here.

    330 Amp hours should have 33 Amps peak charging current or (33 * 12 / 0.77) 514 Watts minimum array size. On a boat you may be limited to how much you can fit, and where. This may call for more expensive monocrystaline panels, many of them, possibly smaller sized, and parallel connections to avoid shading issues.

    Trying to pick up the slack (if necessary) with wind (or hydro - they make trailing turbines for boats) may be difficult too due to space limitations. Most small turbines are not of good quality and do not meet the advertised output power. If the turbine and solar can be reasonably small and matched you can use a single diversion controller to handle both.

    I don't think you'll find a 260 Watt 30 Amp panel: specs on a 260 Watt panel would likely be 30 Vmp and 8.6 Imp (Amps) requiring an MPPT type controller to adjust the Voltage to proper levels for the 12 Volt system.

    I would not worry about the engine battery specifically, as it can be charged from the house system if needed.
  • Musterpoint
    Musterpoint Registered Users Posts: 6
    Re: New to Solar - Need help figuring out what I really need

    Thanks for all the quick responses, it's greatly appreciated.
    seems like too much panel for that size house battery bank
    AuricTech - I'm starting to realize that may be the case, but I need to understand what I can do about it. Additional batteries would not be an issue, but what would the minimum be?.
    What is your daily load plan
    BB. - At the moment I'm not sure. The boat is new to me (but used) and there are a number of repairs the old owner is completing. Replacing broken mechanical fridge pump with an electrical one is in progress. The plan is to do a power audit when I visit the boat later in June. Once I have more info, I'll update the thread here.
    if you can fit it on the ship
    The plan is to place 2 above the cockpit and another 2 on the radar arch. Each pair in series, making 2 strings (is that how it works?)
    I presume (correct me if I'm wrong) that your panels are Vmp about 35 volts and Imp about 7.5 amps, and that the 30 amps you refer to is the combined current of the 4 panels in parallel
    vtmaps - Details from the back of the PV panel are below

    Each panel is Monocrystaline and the sticker reads:
    Max Power (PMax) = 260w +/-3%
    Max Power Volts (VMP) = 31.30v
    Max Power Current (IMP) = 8.32a
    Open Current Volt (VOC) = 37.00v
    Short Circuit Current (ISC) = 9.02a
    Maximum System Volts = 600v
    Protection 'A'
    Max Overcurrent Rating = 15a

    Thanks for the output info, I thought the charge controller rating was the max panel rating it could handle.
    Next consideration is the environment... you need something that can handle a marine environment. Outback makes an "extreme" line of controllers. The new "kid" controller by Midnite also comes in a marine version, but is only rated 30 amps... you would need two of them. That may actually be a good idea... if your panels have different orientations or different shadows there would be an advantage to splitting your panels up into two controllers.

    I looked at the Midnite KID Marine they look promising, however when I use their sizing tool, i get the results below:
    Attachment not found.

    With the EXCESSIVE warning, does that mean they're too small. Could I use 2 controllers (one for each string) and get by ok?
    check the parallel wiring to be sure they are not 'laddered'
    Cariboocoot - they are all in parallel, not laddered.

    Thanks again - keep the suggestions coming! I'm learning a lot!
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: New to Solar - Need help figuring out what I really need
    With the EXCESSIVE warning, does that mean they're too small. Could I use 2 controllers (one for each string) and get by ok?

    Try it and see.. tell the string sizer that you have only two panels, and that they are in series.

    Then tell the string sizer that you have only two panels, and that they are in parallel. Note the difference?

    These charge controllers work by down-converting a high input voltage to a lower battery voltage. The less down conversion, the better. If you put your panels in parallel, the input voltage to the kid will be lower and it will handle more power.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Musterpoint
    Musterpoint Registered Users Posts: 6
    Re: New to Solar - Need help figuring out what I really need
    Try it and see.. tell the string sizer that you have only two panels, and that they are in series

    Hmm, thanks for the suggestion vtmaps ... I guess even with 2 x KID controllers it's cutting it a little close:

    Attachment not found.

    I always thought the more watts the better! I never though solar panels could be over powered :blush:

    I've contacted Midnite Solar's Technical support, asking for details on the difference between their KID (marine) and Classic (domestic) controllers. Using the same data on their Classic sizing tool both the 150 & 200 Lite models can handle these panels fine. Now I need to understand the drawback of either using the Domestic controller in a marine environment; or alternatively what the "EXCESSIVE" warning the sizing tool actually means if I did use 2 KIDS. I'll post their response.

    Also once I have more info about the boats power consumption; I'll post it too. In the mean time, any alternative suggestions are appreciated.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New to Solar - Need help figuring out what I really need

    The warning is in regard to how much clipping the controller would be doing under sunny conditions. If the panel output could potentially provide >30 Amps for a given system Voltage that power would be clipped. This starts as a minor nuisance and works its way up to a major wasting of money on panels as the power would never be fully utilized. A small amount over is not a problem.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: New to Solar - Need help figuring out what I really need

    That small amount of clipping is usually around a 0.77 derating of the array.

    For example, a 12 volt system with a 30 amp MPPT controller could "cost effectively" go upwards of:

    30 amps * 14.5 volts charging * 1/0.77 panel+controller derating = ~565 Watts

    And you will have a few hand fulls of hours per year of clipping (cool/clear days). If you have sub freezing conditions, you could get a bit more clipping in the winter (very cold/clear days, higher than average Vmp for array = more power in cold weather).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Musterpoint
    Musterpoint Registered Users Posts: 6
    Re: New to Solar - Need help figuring out what I really need

    Cariboocoot, BB., thanks for your help. Can you explain clipping to me in a little more detail please?

    Do I understand this correctly?:
    Assuming in my case i have 2 strings of 2 panels as discussed above, each string with its own controller. Now, most of the time they won't be at full output of 520w per string; so each controller won't see a issue. But when the panels reach a point close to peak output, it's too much for the controller, so is that when 'clipping' occurs? Does it simply dump some of the overcharge to ground or cut the 'feed' from the panel or something else?
    Also, can it that affect the rest of the electrical system in any way?

    Thanks again !
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New to Solar - Need help figuring out what I really need

    When a controller 'clips' extra power it simply doesn't pass it. The output of a controller is limited to its Amperage rating. The Kid is a 30 Amp controller. If you have it on a 48 Volt system with 1870 Watts of panels all it will put out is 30 Amps. If you have 2000 Watts of panels all it will put out is 30 Amps. Above the usual 'typical' derating you're wasting money on PV that will do nothing.

    520 Watts on a 12 Volt system we'd figure to produce (520 * 0.77 / 12) 33 Amps. The controller will only pass 30 Amps, so that 10% more power available from the panels simply isn't realized. It does not harm anything.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: New to Solar - Need help figuring out what I really need

    With "switching power converters"--They naturally are able to control current flow though their circuitry.

    A PWM "simple" charge controller is nothing more than a computer controlled "on/off" switch. Just like your light switch, there is no ability to control/limit current flow. If the load current draw is too large--There will be too much current flow and the wiring/switch (transistors) will be over heated/damaged/cooked.

    A MPPT charge controller uses at its very basic--A switch connected to an inductor. And a "fly back" diode also connect to the switch/inductor junction.

    When the switch is first turned on, the current flow is zero and rises the longer the switch is closed. So--Current flow is "regulated" by the inductor (no damaging surge current). At some point the switch is turned off, and the inductor wants to keep the current flowing--The inductor "sucks" current from the fly back diode instead and the current flow starts to fall to zero (based on the stored energy decay in the inductor).

    Turn the switch (transistor) on again, the the current starts flowing through the inductor again. Do this a few hundred times a second, and vary the "closed" and "open" ratios--You have a PWM controlled buck mode switching down converter:

    Buck converter
    - Wikipedia, the free encyclopedia


    Buck converters are very interesting and quite simple as switching power supplies go. Also they are reasonably cheap, rugged, reliable, stable, and efficient.

    Clipping is when the computer controlled switching circuit for the MPPT controller simply limits the average output current by limiting the "on ratio" of the switch.

    No power is "dumped" (solar panels can be "turned off" when the sun is shining, no problems). And if you don't "over panel" very much (the ~0.77 derating factor), the number of hours of clipping per year is not very much (usually the limit is probably a few minutes or an hour at most on rare days--And the "clipping" is (for a random example) the difference between a 30 amp vs 33 amp output (if 10% over paneled).

    Does this make sense?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    Re: New to Solar - Need help figuring out what I really need

    Just throwing this question out there for consideration:

    Given the shadow issues on a sailboat (where even the shadow of a line in the rigging might knock out a panel's production temporarily), would more smallish panels, situated so as to minimize the number that might be in shadow at any given time, work better than a few largish panels? Obviously, this would complicate the wire runs from the panels to the charge controller, but it has the potential of increasing the average power production (unless I'm completely off-base, which has been known to happen, even in areas of knowledge in which I have much more training and experience... ;) ).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New to Solar - Need help figuring out what I really need
    AuricTech wrote: »
    Just throwing this question out there for consideration:

    Given the shadow issues on a sailboat (where even the shadow of a line in the rigging might knock out a panel's production temporarily), would more smallish panels, situated so as to minimize the number that might be in shadow at any given time, work better than a few largish panels? Obviously, this would complicate the wire runs from the panels to the charge controller, but it has the potential of increasing the average power production (unless I'm completely off-base, which has been known to happen, even in areas of knowledge in which I have much more training and experience... ;) ).

    This is in fact quite often the case. The shading issues can be many and varied on a boat.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: New to Solar - Need help figuring out what I really need
    AuricTech wrote: »
    would more smallish panels, situated so as to minimize the number that might be in shadow at any given time, work better than a few largish panels?

    Be sure the 'smallish' panels are in parallel... a series string is only as good as its shadiest panel... sort of... it depends on the panel configuration and its bypass diodes.

    If your panels do have different exposures or shadows there can be some advantage to using multiple controllers (as I mentioned in post #4 in this thread).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Musterpoint
    Musterpoint Registered Users Posts: 6
    Re: New to Solar - Need help figuring out what I really need

    BB. Cariboocoot, Thanks. It does make sense. I'm getting a much better understanding of how PV works. I was concerned 'clipping' was damaging, but it's more like just wasteful of your PV output.
    a series string is only as good as its shadiest panel
    The intention is to place two panels above the cockpit and two on top of the radar arch. Really, there's no 'ideal' places to mount them on a boat, with the constant change in orientation and hundreds of square feet of fabric flopping around. It's always going to be a compromise of sorts.
    The ones on the cockpit will suffer more shading from the boom and sails when the sun is lower in the sky and I accept that. The pair on the radar arch will only really suffer shading when heading into the sun with it low in the sky. The rest of the time they'll be pretty clear, high up hanging over the stern of the boat.

    However, thanks to this thread I know I should split them into separate strings, at least between cockpit and arch, maybe even separate the cockpit out as single panel strings. The possibility of using separate controllers is still a little unclear; as the longer term plan is to add a wind generator and possibly a small gas/diesel generator, depending on what this setup is going to cost me.

    So, knowing what I'm trying to do in the long term and what I'm trying to do it on; what would your ideal wish list of components be, allowing for the add-ons? The only thing I own at the moment are the panels, so its a 'green field build'. This'll give me a some product combinations to research and help shape the big picture.

    Thanks!
  • Musterpoint
    Musterpoint Registered Users Posts: 6
    Re: New to Solar - Need help figuring out what I really need

    Guys, thanks for your input. I've been emailing back & forth with Ryan from Midnight's Tech Support.

    He has also confirmed that 2 KID's will be fine in this scenario & I can ignore the "EXCESSIVE" warning.

    He told me there's a KID for Wind due to be released in the near future. No date yet, but did confirm it has different software and a clipper specific to Wind.

    Also, in follow me mode, you can connect up to 12 KID's (i assume including the Master)

    So, thanks to you guys I have a basic design & wiring diagram that can handle my PV panels AND easily expand to add wind & backup generator!

    You rock!