UPS and Approx 1200 watt solar

drraptordrraptor Solar Expert Posts: 205 ✭✭
I want  to build a setup with the following 
4x 315 canadiansolar CS6U-P http://www.canadiansolar.com/solar-panels/maxpower.html 
UPS according to the system either 24v or 48V 
2 x 12V 200A flooded batteries or 4 x 12V 200A  flooded batteries 
MPPT charge controller. 

Which will be better 24V or 48V and which MPPT charger controller ? 

The load is
  • 2 x Ceiling fans wattage around 80-120W only one will be used mostly 
  • 3 x 14W LED bulbs only 2 will be used regularly 
  •  1 x 5W LED bulb in Washroom 

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    The issue is not 24 or 48 volts, but battery capacity.  As far as your loads go, you could build this as a 12 volt system.  btw, is this an all DC system, or will you have an inverter?

    The real question is how much battery capacity do you need.  What about autonomy... how many cloudy days can you go without running the generator? 

    Once you know your battery capacity, you can figure out a system voltage and battery configuration.  The batteries you mentioned are 2.4 kwh each.  Four of them at 48 volts is 9.6 kwh.   You could also use four 6-volt, 400 ah batteries and have the same capacity at 24 volts.   Or get six 2-volt, 800 ah batteries and have the same capacity at 12 volts.

    Unless you have plans to expand the system, or have long DC runs, a 12 volt system may be the most reliable system you can build.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    You might look around for some other ceiling fans... There are more efficient versions, and even some DC versions (at least a few years back). Drop this search string into google (or click the link below) for some past threads:
    https://www.google.com/search?q=site:http://forum.solar-electric.com/+dc+ceiling+fan

    120 Watts for a ceiling fan is a very significant load (if you run it 12 hours per day, that is about the same energy usage as a full size Energy Star rated refrigerator/freezer). A DC fan could be 1/4 that load...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drraptordrraptor Solar Expert Posts: 205 ✭✭
    UPS act as inverter + charger. 
    The cable from Solar panel to Charge controller will be more than 50fts if I place it at ground floor. 
    I don't have exact wattage for ceiling fans but I will check.  
    how long I can run these load using these 2x 200AH batteries 
  • jonrjonr Solar Expert Posts: 1,384 ✭✭✭✭

    I am available for custom hardware/firmware development

  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    edited July 2016 #6
    Just to show the math based on what you have said so far...
    • 2x 14 watt LED * 7 hours per night = 196 WH
    • 1x 5 watt LED * 2 hours per night = 5 WH
    • 1x 120 Watt fan * 12 hours per day = 1,440 WH
    • =====================================
    • 1,641 WH per day
    If you use 12 volt * 200 AH * 2 batteries, with 2 days of storage and 50 maximum discharge, assuming 85% AC inverter (unless you go pure DC). Note, the calculation below is a 24 volt @ 200 AH battery bank (two of your 12 volt batteries in series):
    • 12v * 200 AH * 2 batteries * 0.85 inverter eff * 1/2 days storage * 0.50 maximum discharge = 1,020 AH per day (nominal)
    So, your above numbers (again, just to really show the math, and how reducing fan usage/power can really save you a lot of energy), you would need a ~60% larger battery bank to meet our rules of thumb for balance system design and storage/usage.

    And I forgot you are in Pakistan (at least your IP Address)... For Islamabad, PK:
    http://solarelectricityhandbook.com/solar-irradiance.html

    Islamabad
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 56° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    4.81
     
    5.06
     
    5.69
     
    6.35
     
    6.63
     
    6.56
     
    Jul Aug Sep Oct Nov Dec
    5.77
     
    5.52
     
    6.25
     
    6.76
     
    5.91
     
    4.79
     
    For your 4x 315 Watt panels, drop the bottom 3 months (cooler weather, less fan), fixed array, November sun (5.91 Hours of sun average):
    • 1,260 Watt array * 0.61 DC off grid system eff * 5.91 hours of sun per day (NOV) = 4,542 WH per day (DC system)
    • 1,260 Watt array * 0.52 DC off grid system eff * 5.91 hours of sun per day (NOV) =3,872 WH per day (AC system)
    And, to finish up, 5% to 13% rate of charge--Recommend 10% or higher rate of charge for full time off grid system:
    • 1,260 Watt array * 0.77 panel+controller derating * 1/0.05 rate of charge * 1/24 volt battery bank = 809 AH  24 volt maximum battery bank
    • 1,260 Watt array * 0.77 panel+controller derating * 1/0.10 rate of charge * 1/24 volt battery bank = 404 AH @ 24 volt nominal battery bank
    • 1,260 Watt array * 0.77 panel+controller derating * 1/0.13 rate of charge * 1/24 volt battery bank = 311 AH @ 24 volt minimum battery bank
    Notice that I really have not said 12/24/48 volt battery bank... Nominally, I would suggest that >800 AH battery bank, you should step up to the next higher voltage bank.

    Some of the choice drops back to what you can get for DC appliance voltage (if you stick with DC)--You might find DC fans through China, if you do not have them locally.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drraptordrraptor Solar Expert Posts: 205 ✭✭
    So I should use 4 batteries at 24V with 2 in series and 2 in parallel ? 
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    drraptor said:
    So I should use 4 batteries at 24V with 2 in series and 2 in parallel ? 
    The most optimal design is a single string (avoid parallel batteries).  Those 4 batteries in series (48 volts) will have the same capacity as they have in series/parallel (24 volts).

    Are there any other batteries you can use?  A single string of 800 ah batteries at 12 volts, or 400 ah batteries at 24 volts will have the same capacity.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • drraptordrraptor Solar Expert Posts: 205 ✭✭
    larger batteries are not so easily available  but I can check 
  • JohannJohann Solar Expert Posts: 245 ✭✭✭
    The way I understand is that many UPS are not pure sine-wave boxes.
    Wouldn't a pure sine wave inverter better to use than a UPS that may be a modified sign wave to start with.
  • mike95490mike95490 Solar Expert Posts: 9,022 ✭✭✭✭✭
    Also, many UPS's only have about a half hour thermal capacity, long enough to run the inverter, heat it up, and the batteries are flat by the time the -deleted $5 cooling fan- is supposed to come on,    Using a large battery and multi-hour duty cycle may overheat the UPS.
    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 ,

  • MarkCMarkC Solar Expert Posts: 194 ✭✭✭
    drraptor said:
    UPS act as inverter + charger. 
     
    I don't believe you stated what UPS you are considering.  I'm very familiar with the APC/Schneider line of Smart-UPSs of essentially all capacities.  Some comments:
    1.  The 48 VDC UPSs are very robust and designed for multiple backup battery packs - so they can operated essentially continuously - especially if not at max load.   However, the efficiency (of the older models in particular) are not as high as dedicated off-grid inverters (in general) - especially at low loads.
    2.  The built in charging systems are limited and are not sufficient for off-grid battery systems.  It appears that you are only using the DC/AC inverter section anyway - so this may be irrelevant.
    3.  All the "Smart UPSs" are sine wave except the SC-450 (the smallest they make) - it is a modified sine wave.

    Let me know what UPS you have and I might be able to help determine how good a "fit" it is with your system.

    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
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