first time solar dummie [posting # 2 ]

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
I'am sorry, from the answers I have received from my first posting. It would seem that I did not frame my question properly. what I am looking for is the largest,[ in what series/parallel array set up] six panel array to put on my moterhome. I have a Xanterx wx-60amp-150volt charge controller , that i would like to use .I have room for four 12volt battery's . look at buying the Concorde PVX-258 OL solar battery with 24hr rate of 258 amp hours. [ leave at 12volt or set up for 24 volt ? ] to hard wire in a pure sine wave inverter 5000/9000 watt. [comes 12volt or 24volt ] . I know I will not be able to run all my 120volt appliances. I'am looking just to run a 1000watt Air Conditioner all day [HOT IN ARIZONA ] and charge the battery,s so it will run all night. [ is this possible ?] if there is any power [ day or night ] left over to use more 120volt appliances that would be nice, but not important. I hope I have made my question easier to understand. thank you for any help i can get.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #2
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    Re: first time solar dummie [posting # 2 ]

    Swamp Cooler? Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,463 admin
    #3
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    Re: first time solar dummie [posting # 2 ]

    Assuming the array meets the rest of the maximum input ratings of the controller, my math looks like this--Assume 0.77 array+controller deratings/losses, the maximum cost effective array size would, roughly, be:
    • 60 amps * 14.5 volts charging * 1/0.77 = 1,130 watt array @ 12 volt bank
    • 60 amps * 29.0 volts charging * 1/0.77 = 2,260 watt array @ 24 volt bank
    If you are in colder areas, you may do better than 0.77 (possibly 0.82). If you are in very hot areas, then you may do a bit less.

    Again--this is not a physical limitation. The MPPT charge controllers (as a family) all have the ability to limit output current (safely and reliably) to their maximum listed output rating.

    PWM controllers do not have this ability, and you have to derate the solar array to keep from damaging PWM controllers.

    By the way, typically for a 150 VDC maximum input voltage MPPT charge controller, the STC rating of the array should be a maximum of ~100 VDC... Any higher voltage, then on very cold days (below freezing), the Voc of the array may exceed 150 VDC and could damage the charge controller (note--most companies offer "calculators" for checking array configurations).

    Is this the question you where looking to be answered?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,463 admin
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    Re: first time solar dummie [posting # 2 ]

    By the way, you should see if you can use a Sanyo (or other equivalent) Mini-Spit AC (or heat pump) unit... They are very friendly for off-grid power systems.

    Sanyo mini split AC (inverter/variable speed)

    And why a 5,000 watt (9,000 watt max surge rating?) TSW inverter? That would easily power my entire 3 bedroom suburban home quite nicely (I don't have A/C and use natural gas for various heating of air, hot water, cooking...).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    Hi dd,
    Well, many things are quite realtave. For example, regarding the PV array, PV modules come in many dimensions. It might be best is you could indicate the area that you have for the PVs.

    Regarding the Inverers, a 5000 watt, or 9000 watt 12/24 volt inverter simply does not compute. The currents at 12 & 24 volts at these power levels are simply astronomical. No company can meet these specs. 5000 watts from a 12 volt battery is probably over 500 amps. Cabling to this inverter, and within it is just HUGE. So large that it is almost impossible to wire the output circuitry -- usually some form of Transformer. IMHO, any company that offers the two above inverter power levels at 12/24 volts is not credible.

    And regarding the A/C. You do have one value, the power, but the duty cycle of the A/C is a very important piece of missing info.

    BB Bill's link to the Mini-Split A/C could help, altho, cooling requires a lot of power.

    The one good thing is that AZ often has wall-to-wall sun.

    Just my attitude. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    And you want to run all this on 6 panels?
    Methinks you're in for a rude awakening.
    It's a shame, but we in North America have been brought up to overuse and waste energy to the point where we consider such overuse and waste to be normal and our right. And many folks believe all they have to do is stick a couple of panels on the roof and all their energy problems are over.
    It's definitely NOT my intention to be, or appear to be harsh, rather it's my honest, up front opinion that you're going to have to totally rethink what you can do and where you want to go with this project.
    Don't give up, at least not yet, keep asking questions, the guys here know what they're talking about.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    hi again dd,

    Please look at the detailed Reply #2 in this thread (your first post):
    http://forum.solar-electric.com/showthread.php?t=13172

    I had forgotten about this thread, and your outline of the panels you were considering.

    One important bit of information is your exact location (more or less). It will affect the amount of sun you could receive on an average day. As others noted, RVs are often subject to shading. And shading can reduce the amount of A/C that you would need, but at the same time reduce the amount solar power you make.

    In looking at the nominal Latitude for AZ, the concern about panel tilt should not be much of a concern for the Summer -- optimum for Phx, AZ is about 4.5 degrees. Other seasons would like additional uptilt, but the cooling demands should be reduced in Spring/Fall.

    If the average humidity at your location is low, a Swamp (Evaporative) Cooler could save lotsa electricity, altho, they do consume quite a lot of water.

    Many trade-offs, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    Pretty simple math. A 1000 wat a/c unit running 24 hours will consume 24 kwh/day.

    Not counting any system loses, and assuming 6 hours of good sun, you would need a 4 kw system just to power the a/c! No RV on the planet could carry a 4 kw system. Add in system loses, STC, ECG and that systEm might approach 8 kw.

    On a related note, 1 kw a/c will draw ~90 amps from 12 vdc, 45 from 24vdc. One would need a huge battery bank to deliver those kinds of currents for very long!

    Tony
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]
    icarus wrote: »
    Pretty simple math. A 1000 wat a/c unit running 24 hours will consume 24 kwh/day.

    Not counting any system loses, and assuming 6 hours of good sun, you would need a 4 kw system just to power the a/c! No RV on the planet could carry a 4 kw system. Add in system loses, STC, ECG and that systEm might approach 8 kw.

    On a related note, 1 kw a/c will draw ~90 amps from 12 vdc, 45 from 24vdc. One would need a huge battery bank to deliver those kinds of currents for very long!

    Tony

    Well most AC units have a duty cycle if sized correctly, but a 1000 watt one in anything but a small room is probably a 100% duty cycle.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    I was just quoting the poster desiring to run "a 1000 watt a/c unit all day, and all night,, because it is hot".

    Like you say, a 1000 watt unit will probably have a duty cycle of near 100%.

    I know that in the brutally hot ( and humid ) days we have occasionally I n the summer, I have a 5000 btu window unit, running in a well insulated 500 sq ft house and it can't begin to keep up. We resort to spraying down the house with lake water in the evening to suck of as much heat as possible!

    Tony
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: first time solar dummie [posting # 2 ]

    As usual it comes down to getting accurate numbers for the loads. Otherwise you're just guessing at equipment and will likely be disappointed with the result.

    5 kW 12 Volt true sine inverter? Whose is that? Likely the notorious AIMS. Do not buy it, as 5kW on 12V is not sensible.

    The need to run a 1kW A/C is a big power requirement. Its start-up will be huge, and even if it only runs 1/3 of the time it will use more Amp hours than is practical on a 12 Volt system.

    Get a Kill-A-Watt meter. Get a generator. Run what you need through it and get some numbers that are real. This is the best way to do a design that will work.
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