Post-Irma Caribbean Small Solar System

SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭
Dear All,

I returned two days ago from the Caribbean nation of Anguilla, which was hardest hit by Irma along with St. Martin. I am attempting to build a solar system that will power well pumps (usually 1/3, 1/2, or 3/4 HP, which has a max wattage that should be below my system's capabilities), so people can have water again. The electric grid was destroyed by Irma, and we're expecting 4-8 months of no electricity. 

I'm trying to keep the system around $1,000. Can you please advise if there are any problems with this system (one with more expensive charge controller and batteries, one with cheaper)?

System 1:
Morningstar Prostar PS-30M Solar Charge Controller - $191
Crown AGM 12V 98 AH Battery (X2) - $375.94
Power Bright ML2300-24 Power Inverter - $249.99
Renogy 280 Watt 24V Solar Panel - $252.99
+12 AWG wiring
Total before taxes and shipping = $1,069.92

System 2:
Victron MPPT 70 | 15 Solar Charge Controller - $99
Universal UB121000-45978 12V 100AH (X2) - $318.98
Power Bright ML2300-24 Power Inverter - $249.99
Renogy 280 Watt 24V Solar Panel - $252.99
+12 AWG wiring
Total before taxes and shipping = $920.96

I know the inverter is not the best, but other inverters are just way too expensive. My main question is, will it work?

Thanks so much for your help, and for giving power to those in the dark in the Caribbean!

-James


Comments

  • BB.BB. Posts: 27,694Super Moderators admin
    You really need to look at the well pump. That is a small battery, but AGM batteries can supply higher surge current and could run a 1/3 or 1/2 HP well pump for some time per day (an hour or so). If water is used at night, an hour or so of power (battery storage).

    I understand that water, lighting, and a small radio would be a huge help for those folks hit by multiple hurricanes and start their rebuilding.

    Also, the panel you have listed appears to be a Vmp~30 volt device. To charge a 24 volt battery bank, you need a Vmp~36 volt panel with a PWM controller. The configuration you have will not work well (solar panel voltage is not high enough to charge a 24 volt battery bank). If you switch to a 12 volt battery bank, your system would work (with an MPPT charge controller).

    Having some sort of meter (in charge controller or similar) is going to be critical for folks to understand how to run their system (do not run the battery flat, understand to let it recharge the next day, remember to turn on inverter only when they need to run AC power--leaving the inverter on 24x7 will burn more than 1/2 the power supplied by the solar panel, etc.).

    And, this is a MSW (Modified Square/Sine Wave) AC inverter... Not great for running motors and small AC appliances with wall transformers (it really depends on the AC load, probably 80% will work OK and ~10% will have a shortened life--Very difficult to predict).

    I would suggest a Samlex or Cotek (or similar) AC PSW/TSW (pure/true sine wave inverter). Or look at supplying a 12 volt DC water pump with the system.

    For the sake of argument, lets say the system support ~400-600 WH per day (280 Watts * 0.52 system eff * 4 hours of sun = 582 WH per day) and the batteries last ~1 year (hot climate, heavy starting loads, and people that do not really understand solar power).

    That is a very small system. And I would ship some sort of small LED lights with it (people will connect lights to the system--Too large of AC power draw will kill the battery bank/not let solar panel fully recharge battery bank).

    I would suggest that you build such a system and connect a pump to it and see how it performs over a few weeks (as somebody in the field would run the system).

    I fear that the end user in the field will simply run the system until the battery goes dead. Then it recharges some the next day, and as soon as they can, they will run it again until it is dead again. The battery may last a few weeks at best when operated this way. And they will be left with a crippled system that may start a 1/3rd HP pump and run it for an hour during high sun.

    Most people do not understand the care and operations of off grid solar power. And while the system may operated well (the AC inverter is questionable), and any solar system will just will not survive the expectations and usage of the folks in the field unless there is good training and support.

    If you go with a solar panel + DC direct water pump (surface or in-well pump--not going to be cheap)--Get rid of the (troublesome/short life battery, don't bother with AC inverter), and a recharger (AA NiMH batteries) for radio+flashlights--It might be more "rugged" and forgiving. If the users kill their AA batteries, can replace the batteries for a few dollars (need more research to find "good" 12/24 volt solar battery charger).

    https://www.solar-electric.com/sh93susowapu.html
    https://www.solar-electric.com/902-100.html
    https://www.solar-electric.com/902-200.html
    https://www.solar-electric.com/2088-574-534.html

    For an "optimal" system design, you should talk with somebody that has the detailed knowledge to set up a panel+controller+pump (no battery) system like our host NAWS. Then you may need to supply pumping, filters (most pumps do not like dirt/sand), etc. And how many people on the islands have access to a fresh water well vs relying on central water facility/desalination?

    I understand your heart to try and help these folks--But this is a complex task.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭
    edited September 2017 #3
    BB. said:
    You really need to look at the well pump. That is a small battery, but AGM batteries can supply higher surge current and could run a 1/3 or 1/2 HP well pump for some time per day (an hour or so). If water is used at night, an hour or so of power (battery storage).

    I understand that water, lighting, and a small radio would be a huge help for those folks hit by multiple hurricanes and start their rebuilding.

    Also, the panel you have listed appears to be a Vmp~30 volt device. To charge a 24 volt battery bank, you need a Vmp~36 volt panel with a PWM controller. The configuration you have will not work well (solar panel voltage is not high enough to charge a 24 volt battery bank). If you switch to a 12 volt battery bank, your system would work (with an MPPT charge controller).

    Having some sort of meter (in charge controller or similar) is going to be critical for folks to understand how to run their system (do not run the battery flat, understand to let it recharge the next day, remember to turn on inverter only when they need to run AC power--leaving the inverter on 24x7 will burn more than 1/2 the power supplied by the solar panel, etc.).

    And, this is a MSW (Modified Square/Sine Wave) AC inverter... Not great for running motors and small AC appliances with wall transformers (it really depends on the AC load, probably 80% will work OK and ~10% will have a shortened life--Very difficult to predict).

    I would suggest a Samlex or Cotek (or similar) AC PSW/TSW (pure/true sine wave inverter). Or look at supplying a 12 volt DC water pump with the system.

    For the sake of argument, lets say the system support ~400-600 WH per day (280 Watts * 0.52 system eff * 4 hours of sun = 582 WH per day) and the batteries last ~1 year (hot climate, heavy starting loads, and people that do not really understand solar power).

    That is a very small system. And I would ship some sort of small LED lights with it (people will connect lights to the system--Too large of AC power draw will kill the battery bank/not let solar panel fully recharge battery bank).

    Hey Bill, thank you for this great response. If I:

    1) Substituted the two 12-volt batteries for two CROWN AGM GC2 6V 220AH batteries
    2) Substituted the MSW AC inverter for a Cotek PSW inverter
    3) Supplied small LED lights to discourage use of more energy-intensive lighting at night
    4) Ensured that inverter was not constantly connected but rather used on a need-basis

    Would that be enough to take this system from dismal to practicable?

    Thanks so much for your insight. This is definitely more of an emergency type of solar system rather than a five-year solution, but if it could provide help for three or four months rather than failing in three weeks, that would be great. 
  • Dave AngeliniDave Angelini Posts: 3,901Solar Expert ✭✭✭✭
    edited September 2017 #4
    Not a 3/4 HP induction motor, probably not the 1/2 HP reliably. The real problem for you is that these pumps are not soft start and not variable speed. If you had that in the design it would work, but of course you can't. Can you get those batteries in Anguilla in "normal" times? Can you do what Bill suggested and use 12V pumps, probably not for a well pump and not in your price range.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Posts: 2,635Registered Users ✭✭✭✭
    For an emergency type system, I'd think about storing water (as opposed to storing solar power to pump the water). Fill a tank when the sun is good, and either gravity feed if there's terrain (not much IIRC) or use an rv DC pressure pump for supply. Storing water is likely to be a lot simpler and cheaper in this situation than trying to design a system to store solar power to run a well pump on demand.

    Also, pump often run on 240v. Are these only 120v?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Posts: 27,694Super Moderators admin
    At this point, I think folks need to wait until the storm clears and emergency response and the residents have a few days to figure out what they will need. I don't know if salt water may have contaminated their ground water/wells (i.e., desalination vs filtering, or perhaps fuel/other contamination), or if water is a bigger issue than power/food/sanitation.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bsolarbsolar Posts: 103Solar Expert ✭✭✭
    hey i feel for you i got the weak end of irma here in north florida- power out for 5 days only here ...... as mentioned above trying to make a small system to run a high power well pump is going to be dicey ... if you have access to fuel, using a generator to fill a large holding tank that could supply several places would be a better option .. you could fill it and then run a 12v rv pump on a single panel single batt system no problem .. typical household use if theyre frugal will average around 100gals a day .. you 'could' use solar to fill a tank from a ~1/2 hp 120 well pump but i would want at least 6 large panels and 4 batts, and preferably double that,  to support that kind of load.
  • mike95490mike95490 Posts: 7,800Solar Expert ✭✭✭✭
    I doubt those 12v inverters would start those well pumps after a week.  
     You may be better off with a gasoline powered generator and run the pump from that, and fill a holding tank.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • westbranchwestbranch Posts: 5,087Solar Expert ✭✭✭✭
    Solar Caribbean, I think it was in at least one of the above but not really clearly stated....follow the KISS priciple... the simpler the better, especially with a shortage of all resources at this time. that said...
    Can you locate a 1000gal  (or less) clean tank and put it in an elevated spot so that once the water is in it no additional power is needed to fill smaller (1 to 3 gal)  jugs for home use initially and then as resources (piping for the water etc) are available the system can be powered with a (1/3 Hp) pressure pump running off a larger (24V or 48V) battery bank with adequate solar to recharge.
    Here is a link to a project in Haiti to see just what might be needed at the end of your journey...
    http://midniteftp.com/forum/index.php?topic=3730.msg36045#msg36045

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • OceanOcean Posts: 40Registered Users ✭✭
    Indeed Sir, even with such good intentions, you really must know exactly what pump you are designing your system to run.  And most standard well pumps will pull at least twice if not three times their rated capacity at startup.... for at least a couple seconds.  And your batteries MUST be able to supply full power / amperage required by the surge, or the pump will not start - but rather it will stall, and overload the system.  You have to know the details to really make it work.  Finding a certain well / pump for which you can get details would be a start.

    If you contact anyone who is in a position to pull and replace a well pump, than you might look into the Grundfos SQFlex series of pumps, such as the 11SQF2 (down to 300 feet deep)...  these pumps can run directly from solar panels and will deliver water all day while the sun is shining, in proportion to the amount of power they are given.  They have a huge range of voltage they will accept (30 - 300 vDC OR about 50 - 250vAC).  They are super smart and will last a long time so long as they are protected from sand / grit.  Also, they're about $2400... so not cheap but again, can be connected directly to solar panel (anywhere from 100 watts to 1400 watts @ >30v) OR run from a generator of ANY standard output / frequency.  I have one and it's amazing.

    Best Wishes and Luck to those in the path of nature's wrath...
  • SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭
    edited September 2017 #11
    Thank you so much everyone for the great feedback!

    When I was on the island this past weekend, I spoke to the plumbing experts, and they assured me that most cistern pumps are 1/3 or 1/2 HP. The pumps are 120V.

    1/3 HP Well Pump | Startup Wattage = 1,500 | Running Wattage = 750
    1/2 HP Well Pump | Startup Wattage = 2,000 | Running Wattage = 900

    Also, since we typically don't have this kind of water catchment system in the US, I think there's a bit of confusion. The pump typically comes on for a mater of seconds, maybe five times an hour or so. I can't imagine it running for more than a minute at a time. 

    This comes from personal experience, as I lived in homes on the island, and you can hear when the pump is running and when it's not.

    In other words, the energy requirements are quite small. It literally could be 700 watts for 20 seconds, three times an hour, ten times a day. And nothing at night. Ie,

    USE = (700 watts X .2 hours = 140 watt hours) X 10 hours = 1,400 watt hours/day
    CAPACITY = (12 volts X 440 AH) = 5,280 watt hours

    The thousands of dollars, manpower, and material needed to build new catchment systems or above ground systems are completely out of the question at present. Also, trying to do expensive new pumps when people already have pumps in place is unlikely to get compliance.

    Gas/diesel generators that do the trick are available for around $400. But they cost at the very least $140 a week in fuel to run, and fuel is in extremely short supply right now. Not to mention the potential for carbon monoxide poisoning when people place them incorrectly.

    So how does this look:

    CROWN AGM GC2 6V 220AH batteries (X2) for a total of 12V/440AH of batteries
    Power TechON PS1005 Pure Sine Wave Inverter (1500W Cont/3000W Peak)
    Renogy 280 Watt 24V Solar Panel
    Renogy Rover 20A MPPT Charge Controller

    Are those changes helpful? This has more AH, a better charge controller, and a PSW inverter. Does that help?

    If not, what is the key to making the system work? More batteries? Better inverter? More panels? Or a combination of those two? If rebuilding the whole water catchment system is completely out of the question, how can you design the solar system to work?




  • mike95490mike95490 Posts: 7,800Solar Expert ✭✭✭✭
    Those high surge loads (starting the pump motor) are tough on inverters. And I'll bet your starting wattage is much more then you were told.  Try 5x the running power, and that would be close.   No matter where the motor is made & used, they all work the same way.

    Or, run the pump for 10 minutes off the generator, and fill a holding tank, and use a small RV pressure pump to get water to the sink & shower.  10 minutes of fuel per day.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Posts: 27,694Super Moderators admin
    edited September 2017 #13
    An RV motor takes around 40-60 Watts, your larger induction motors + AC inverter are going to take 100's to ~1,000+ Watts to start.

    If there was anyway to pack an RV pump+pickup pipe+pipe (and valve) to tap into the main water pipe--Your solar+battery system will be much smaller, cheaper, and less complex to operate (from an electrical/battery maintenance point of view).

    If the cold water plumping is usually PVC--Cut out a section of pipe and add two valves--One to block the AC pump and the second to block the DC pump water flow (so you do not back pressure the check valves in the "unused" pump). connect the second valve to t-he RV pump. Add check valve and input strainer as needed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • OceanOcean Posts: 40Registered Users ✭✭
    edited September 2017 #14
    Hey @SolarCaribbean

    Can you clarify - you said these people have Cisterns as water catchment.  And the pumps come on for mere seconds 5 times per hour?

    Does this mean that the Cisterns are serving the purpose of a "holding tank"?  How many gallons do they hold?

    What is the function of these 1/3 or 1/2 horse pumps???  Are they deep well pumps?  OR are they actually pressure pumps driving pressure from the Cistern???  If so, are there pressure tanks involved?

    This is important for us to clearly understand what you're dealing with.  Just how are these systems working?  How are the Cisterns being filled???

    It's important because, as was mentioned earlier by Mike, deep well pumps can have a very high surge - and this may be due in part to the fact that most of them are starting under a load (water held above by check valves = pressure against the pump when starting).  Shallow pumps on the other hand, like a jet pump, or something that simply drives pressure from a holding tank, will have a surge much more like you described - like 2x the running watts.  I have a 1HP swimming pool pump - and the running amps is almost 20 amps @120v, but the startup surge is closer to 30 amps... so that's an example.  It has nothing to push against until it draws water from the pool.

    Still, Surging 5x per hour, as you indicated, would be hard on any inverter.  The thing is, you want an inverter that is designed for heavy motor loads.  The inverter itself will be heavy.  I have a 1500 watt Heart Inverter... it's HEAVY (like 45 lbs or something) because it has a relatively massive transformer in it.  You need that.  It can start my 1.5HP Table Saw IFFFF there's enough battery power behind it.  That's the critical point.  And you have to maintain that battery at FULL for it to keep providing that surge power.  If the battery is not kept full, then it will not supply the amps necessary for the surge (it's voltage sill sag too low), and the motor will not reach running speed (therefore stuck in Surge, or Stalled) and so the Inverter will be stuck supplying the Surge current (with not-enough voltage) until it overheats and shuts down or melts down and dies.

    I don't know about the inverter you listed.  But you can tell something about an inverter by it's weight (check "shipping weight").  Some 2000W inverters only weigh 5 or 10 lbs.  They will not last - they will melt down.  You want one that weights 50 lbs.

    Also, to go with your calculation of 1400 watt hours per day, you need BOTH to recover that energy AND Float the batteries.  One 300 watt solar panel can reliably produce about 200 watts for 6 hours on a sunny day - assuming it's placed in a sunny location and facing the sun.  That's only 1200 wHrs per day.  YET LA batteries are only about 50% efficient, so keeping them charged up will require twice the energy than what is pulled from them.

    So realistically, you should be recovering about 3kWhrs per day to run those pumps for 1400wHrs per day and keep your batteries charged up.

    To do that, you need 3000/6 = 500w of panels x 1.5 (efficiency losses) = about 750 or 800 watts of panels.

    So:

    A 1500 or 2000 watt inverter weight about 50 lbs designed for inductive motor loads (Sinewave probably but that's secondary to the weight)

    Your batteries looked good but something you need to understand: YOU said 6v 220Ah x2 = 12v 440 Ah. Wrong.  Unless you meant x4.  Because when you run batteries in series you add the volts, but the amps remain the same.  When you run batteries in parallel the amps add together, but the volts remain the same.  You get one or the other but not both.  Therefore 6v 220Ah (x2) = 12v 220Ah.

    This may be enough battery battery to start those motors, but it will be hard on them doing it 5x per hour.  Four of these batteries would be better.

    Thus:

     (2 or 4x golf carts 6v each wired series / parallel for 12v or all series (if you get 4) for 24v with 2/0 welding cable and appropriate connectors, crimp or screw, and completely coated with vaseline (entire connection and post) or other protective to resist corrosion which WILL happen if you do not protect the connections at the batteries - although this is actually much less of a problem with gels than it is with flooded LA's - but eventually it will happen)
    800 watts of solar panels
    an Mppt Charge Controller of good quality like Outback, Morning Star, Midnight etc.  I don't know about Schneider I don't trust them..

    Your system would operate better if it was a 24v system rather than 12 volt, because volts x amps = watts, and therefore to get the same watts from a 24v system you can cut the amps in half, and AMPS are what produce heat, and heat is what kills inverters and cables.

    Cheers!
    -Ocean
  • BB.BB. Posts: 27,694Super Moderators admin
    I believe these are rain water catchments/cisterns. And, from what I can find, use a small AC pump + pressure tank to move water into the home. Pretty detailed report for the Caribbean.

    http://www.caribank.org/uploads/2013/08/em-rainwater-handbook-caribbean.pdf

    I presume that homes/businesses that need water (dry weather or droughts) can have tank trucks deliver water too.

    Something from the news, even if the houses were still standing--There were areas where entire neighborhoods lost their roofs (which would limit rainwater catchment until rebuilding was well along.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • cow_ranchercow_rancher Posts: 100Solar Expert ✭✭✭
    edited September 2017 #16
    BB I agree, at first I was baffled... thinking that these were well pumps, but remembering my visits to St. Thomas everything is rain water.  An RV pump instead of what is normally used will get water into the homes, RV pumps are also available at boat suppliers.

    Rancher
  • OceanOcean Posts: 40Registered Users ✭✭
    The system you want to build is plug and play for those people who simply want to plug in their existing system / pump and make it work.  Yes it would supply some lights as well.

    But the guys are right about the RV pumps... IF they can be plumbed in to replace / bypass the existing cistern pumps, they can move a little water (2-3 gpm) with one 12v RV (deep cycle) battery and one 12v 200 watt panel and a small 12v pwm controller to keep it charged up.  It's the plumbing in this case that has to be worked out.  Simple for a plumber.
  • mcgivormcgivor Posts: 2,069Solar Expert ✭✭✭✭
    edited September 2017 #18
    Anguilla, being  British, would most likely have cisterns in the attic space, speculation of course, usually with float valves to control water level, if city water is available, in its absence a float switch controlling a well pump would be implemented. If this is the case, lowering the cut in level of the float switch would allow longer pump run, with less frequency. 

     A while back I had a Morningstar,  60A PWM charge controller with 1500W PV ( must be 72 cell 24V nominal, usually 300W + not 60 cell GT panels ) , a 260 AH  24V battery,with a 1 hp pump, I ran this way for over  a year, for about 2 hours per day for irrigation, The pump was a 230V submersible 15 meters down, static water 4 meters, AC run current ~4A, inrush 43A, the inverter was a cheap 2000 W sine wave, which had no problems supporting the load, a 1/2 hp. pump in similar conditions, would be half these values. 
    The advantages of MPPT in tropical environments are minimal, PWM are cheaper so more can go towards PV, it's important to have  more solar than the pump requires, ~50% more. The main purpose of the battery is to support the inrush, and the occasional cloud passing,  you need to keep an eye on things though, clouds can cause the battery voltage to sag, fortunately I only used this setup in the dry season, when clouds are rare, located in the tropics 17°N.

    Just sharing my experiences hoping they may be of help, but keep in mind, this is not a suggestion for an install and forget, left unattended it would probably fail. Using a temporary bypass DC pump would greatly simplify matters and reduce costs by probably 80%, who knows it may be left that way, using the AC pump as a backup. 

      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • BB.BB. Posts: 27,694Super Moderators admin
    McGivor,

    Do you remember the Watt rating of the AC inverter you used?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Posts: 2,069Solar Expert ✭✭✭✭
    Yes Bill, its a 2000W 4000w surge.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭
    BB. said:
    I believe these are rain water catchments/cisterns. And, from what I can find, use a small AC pump + pressure tank to move water into the home. Pretty detailed report for the Caribbean.
    First of all, thank you so much to everyone for the amazing energy and focus on detail I'm seeing in this thread.

    Like Bill said, these are rain water catchments/cisterns, and use small AC pumps. I slightly regret ever using the word "pump," because that kind of threw the discussion in all directions (although I do appreciate the focus on finding root causes rather than treating the symptoms). Thus, to simplify things, rather than focusing on the water catchment system or pump, let's say I want a solar system that powers a children's basketball arcade game.......which uses 2,000 watts to start up, 900 watts to run continuously, and will be run for less than 20 minutes a day, with most use during sunlight hours. The PV system will also be dedicated to use for the pump....I mean.....arcade game.....rather than used willy nilly for anything that people want.

    We have redesigned the system based on our research and your feedback, with a final system of:

    Base System:
    Apex APX12-200 12V 200AH X2 connected in parallel for 400AH total
    Renogy Rover MPPT Charge Controller 12V/24V 20A
    Renogy 280 Watt 24 V Panel X2 connected in parallel for 560 watts total
    Power TechOn PS1005 inverter (1,500 watt continuous / 3,000 watt peak)

    Cabling and connectors:
    Four Star Solar MC4 10 AWG - 15' Cable Extension X2 
    MC4 Branch Cable Coupler (neg) - 2 Male 1 Female
    MC4 Branch Cable Coupler (pos) - 2 Female 1 Male
    Four Star Solar 2/0 - 12" UL Cable (White) 
    Four Star Solar 2/0 - 12" UL Cable (Red) 
    Four Star Solar 2/0 - 18" UL Cable (White) X2
    Four Star Solar 2/0 - 18" UL Cable (Red) X2

    Also of note, due to the location of Anguilla, we're looking at much closer to 7 usable hours of sunlight than 4, and conditions are great year-round (with the exception of the occasional hurricane of course).

    McGivor, you stressed the need to have more panel wattage than the pump needs, but if the pump is used so little, can a lower total panel wattage be compensated for by the battery capacity?

    Thanks again to everyone. We're obtaining system components imminently, so please provide feedback soon if we're missing something critical.
  • SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭



    Also would someone mind looking at the connections and seeing if everything is right?

    -James
  • mcgivormcgivor Posts: 2,069Solar Expert ✭✭✭✭
    If the load is, as you say only used for 20 minutes, you should be able to get by using the batteries, since they will be replenished immediately, but you are withdrawing twice what's going in approximately, keep in mind the maximum output from the panels will occur between the hours of 10:00 & 14:00, outside this, it's less,based on latitude 18°N. Since the pump is not working against a head, being primed by the cistern, an assumption, the duration of surge would be reduced, making the whole project more feasible, according to your design.
    Please understand all the valuable comments made by others, are made based on information provided with the intent of seeing you succeed, designing a system for long term use is very different to a temporary, emergency situation, with a limited budget. Based on the diagram provided, the only thing missing is fusing, battery to inverter being the most important. My previous post, regarding having the array 50% larger than the pump consumption is based on a full time off grid situation , needing  to power other loads at night, if the majority of loads are within the prime time, so to speak, you are probably ok, just remember this is not a convenience, but rather a necessity, conservation is paramount.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • AguarancherAguarancher Posts: 270Solar Expert ✭✭✭
    I would think the inverter should be connected to the battery and not ran through the charge controller.
  • EstragonEstragon Posts: 2,635Registered Users ✭✭✭✭
    A single 20a charge controller is marginal for 400ah of battery. 560w of panel might produce about 560x75% derate ÷14.5v charging = about 29a. I'd consider a second controller, or a larger PWM.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Posts: 2,069Solar Expert ✭✭✭✭
    I would think the inverter should be connected to the battery and not ran through the charge controller.
    Absolutely, missed that, always good to have other eyes, noticing relevant points.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • AguarancherAguarancher Posts: 270Solar Expert ✭✭✭

    I thought we used to have ‘stickies’ with a basic wiring diagram for simple off grid set-up, but I couldn’t find one. It would be helpful to have one as the first post in off grid or beginners section.


  • BB.BB. Posts: 27,694Super Moderators admin
    Be careful with the "hours of sun" per day... Many times, folks over estimate the amount of energy they can collect. For example, a fixed array facing south for Anguilla:

    http://www.solarelectricityhandbook.com/solar-irradiance.html

    The Valley
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 72° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    5.97
     
    6.55
     
    7.04
     
    6.86
     
    6.71
     
    7.16
     
    Jul Aug Sep Oct Nov Dec
    7.10
     
    6.57
     
    6.38
     
    6.23
     
    5.67
     
    5.68
     
    If you assume that you need a minimum of 900 Watts * 1/3rd hour per day:
    • 900 Watts * 1/3 hour per day = 300 Watt*Hours per day
    And your system of 560 Watts would produce on an "average day" in December:
    • 560 Watts * 0.52 system eff * 5.68 hours of sun per day (Dec) = 1,654 Watt*Hours per day (Dec)
    Gives you ~1,354 WH of "excess" solar power for other uses. A 1,000 WH per day system is good for LED lighting, radio, cell phone charging, laptop or tablet charging (and water pumping).

    You need breakers to the battery bank... For the solar charge controller, a minimum circuit breaker (and supporting cable to battery) of:
    • 560 Watt array * 1/11.5 volts minimum battery charging * 1.25 NEC derating = 61 amp breaker/wiring support (~60 amps).
    The charge controller looks a bit small (for optimum) charging--You appear to be walking away from almost 10 amps charging current during the middle of the day (controller will work fine and limit its output to 20 amps):
    • 560 Watts * 0.77 derating for panels+controller * 1/14.5 volts charging = 30 amp recommended minimum typical MPPT controller
    If you use a 20 amp maximum controller, then the battery wiring+breaker would be:
    • 20 amps MPPT charge controller output * 1.25 NEC derating = 25 amp minimum breaker+wiring
    You don't need a switch/breaker on the PV input, but sometimes it is nice to have at least a switch to cycle power to the charge controller (all switches off, turn on battery bank first to boot controller, then turn on PV array).

    The AC inverter--Assuming that it uses ~20 watts just turned on... Then the self consumption of an inverter running 24x7:
    • 20 watts * 24 hours per day = 480 Watt*Hours per day.
    The AC inverter you selected does have a remote on/off switch--Which is nice, if folks will turn the inverter on when water is needed. If not, it will "waste" a fair amount of power (I did not find any details on inverter power consumption--Guess 10-20 watts typical).

    Wiring the remote to the system pressure switch would be nice (inverter turns on when water is needed)--But may not be practical (have to rewire the installed pressure switch, splice into remote panel--And folks may want AC power for other things and turn on inverter anyway).

    Cabling between charge controller and battery bank needs to be short and heavy (low voltage drop). For example, if 3 feet of wiring and 30 amps with a maximum of 0.10 volts drop:
    http://www.calculator.net/voltage-drop-calculator.html
    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&voltage=12&phase=dc&noofconductor=1&distance=3&distanceunit=feet&amperes=30&x=71&y=4
    • 3 feet of cable (one way run), 30 amps, and 6 AWG gives you:
    Voltage drop: 0.071
    Voltage drop percentage: 0.59%
    Voltage at the end: 11.929

    And for the AC inverter... Wiring also needs to be short and heavy:
    • 1,500 Watt * 1/0.85 AC inverter eff * 1/10.5 batter cutoff * 1.25 NEC derating = 210 Amp minimum rated breaker+wiring
    • 1,500 Watt * 1/0.85 AC inverter eff * 1/10.5 batter cutoff = 168 Amps
    And voltage drop wise, 0.50 volts maximum drop. Assuming 3 feet of wiring and 168 amps, that would be:
    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.5127&voltage=12&phase=dc&noofconductor=1&distance=2&distanceunit=feet&amperes=168&x=66&y=14
    • 2 feet of cable (one way), 168 amps, and 2 AWG cable:
    Voltage drop: 0.11
    Voltage drop percentage: 0.92%
    Voltage at the end: 11.89

    Having 12 volts is nice for running 12 VDC loads (battery chargers, lighting, radio, laptop computer), but it does put a severe crimp in plans when running heavy loads (1,500 Watt of AC inverter)... And that is not including the additional surge current for starting (why I used a sort of conservative value of 0.5 volt drop at running current to allow 1 volt drop at 3,000 watts of surge).

    If you do not have short heavy connections to the battery bank, you lose the ability to start loads with high surge current and less than full battery bank.

    For connecting your two batteries in parallel (I would prefer 2x 6 volt batteries at ~400 AH each--But did not find any for that brand), you need to wire them on the "diagonal" to ensure that they charge/discharge evenly:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarCaribbeanSolarCaribbean Posts: 6Registered Users ✭✭
    If you do not have short heavy connections to the battery bank, you lose the ability to start loads with high surge current and less than full battery bank.

    For connecting your two batteries in parallel (I would prefer 2x 6 volt batteries at ~400 AH each--But did not find any for that brand), you need to wire them on the "diagonal" to ensure that they charge/discharge evenly:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill
    Thank you for these phenomenal responses!

    I am a bit lost on breakers, switches, and fuses. I will do more research, but do you have a specific product that you would recommend for this particular system?

    The cabling I was looking at for connecting charge controller and batteries is listed as 2/0 rather than with an AWG gauge. Is 2/0 what I want? Or should I just get some 2 AWG cable and use that? I liked the look of the pre-made battery connection cabling on wholesale solar because it had the terminal lug connectors on it already.

    Also, based on the numbers you provided, I'm thinking the 18" charge controller-to-battery bank length I'm using is okay and would quality as "short."

    Renogy makes a 40A charge controller that is very similar to the 20A model I listed, so I have upgraded our system to incorporate that.

    The inverter will be directly connected to the battery bank too. 

    I tried to research what you meant by diagonal connection of batteries, but it seems in the diagram I listed, I already have connected in diagonal? 

    Thanks again for the great feedback.
  • BB.BB. Posts: 27,694Super Moderators admin
    Yep, you got the battery wired "diagonally". You want equal wiring resistance between the two batteries.

    Fuses can be a bit cheaper on initial install... But blow a couple of fuses (or don't have any in the drawer at home), you will wish you had breakers. Also, breakers can also function as disconnect switches for servicing. With fuses, you have to add a switch if you want the switch function.

    As to brands/models--You should be working with a supplier you trust to get you the equipment you needs. Cheap thermal breakers (and fuses) may work well, or trip at 1/3rd their rated output. Random parts, random results.

    Note that many folks that deal with AC and DC power are used to over sized circuits with minimal current flow. You have 300 Watt motor (roughly 4 amps) on a 15 amp minimum circuit (if this is 120 VAC 15 amp North American power). When you run solar power (i.e. 30 amp why I highly suggest the 1.25 NEC "continuous power" derating for solar. Running battery charging is many hours at rated current and the typical (even good quality) breakers are usually spec'ed to pop at >100% rated load (seconds/minutes/hours) and not pop at ~<80% of rated load.

    Getting help from a "full service" retailer/wholesaler like NAWS (our host) is a good start (and supports our host who pays the freight for this this forum).

    Once you choose one or several sources for your products, then you can look at their product line(s) and figure out what will be cost effective for your requirements (picking a random/good product from the world of the Internet may not be helpful).

    Also--Since the island you are asking about is a British protectorate, do they use 120 Volts @ 60 Hz or 230 Volts @ 50 Hz (the correct AC inverter). Using supplies that are local to the island (or at least can get there quickly and cost effectively) will be helpful to folks maintaining the systems (get a good price on batteries from China, but 6-8 weeks on a slow boat, then sit on the docks waiting for customs--Always fun). NAWS and others suppliers have experience shipping to the Caribbean. You might have several sources (NAWS can design/build/test systems, get another supplier that has warehousing for batteries on/near the island).

    You can use heavier cable and, in most installations, that is not a problem (other than making sure you can fit the wire in the terminals, plus large diameter cable is very stiff and difficult to bend/pull through conduits/boxes, and every 3 AWG heavier cable, is 2x more copper and 2x the cost). Using wiring charges to Ampere ratings, voltage drop calculators, following/confirming the manual instructions needs to be done everywhere. We have had reports here of Electricians that do only AC wiring that have not a clue what to do with a 12-48 VDC system.

    Whatever you do--I highly suggest you buy at least one set of hardware and build out the system. Then test. There are a lot of details that need to be right before kitting up 100's of systems and shipping them out to the market.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • OceanOcean Posts: 40Registered Users ✭✭
    Echo the last point.: put one system together yourself, and see it work.  Test it on a similar load.  Be familiar with the components.  Have yourself a fully functional kit before you head out.  Breakers are really nice when you realize you need to make changes to your wiring...
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