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Thread: inverter installation for Load Shedding

  1. #1
    Full Member Tonye's Avatar
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    inverter installation for Load Shedding

    Inverter installation.

    This installation was designed for a 4,5 hr load shedding period with an average 1kW load
    and based on a 85% inverter efficiency & a 50% depth of discharge on the batteries.

    Click image for larger version. 

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    Option 1 400 battery cycle life at 50% DOD (the one that was installed)

    4KVA 3.2Kw PSS low frequency 48v inverter (weight 53kg & capable of handling high inrush currents)
    8x 110 A/H deep cycle batteries (weighing in at 240 Kg)
    400 cycle life @ 50% DOD
    (Total weight of Inverter, Batteries & cabinet @ 300kg)

    Total cost including installation R46000.

    Option 2 (Solar ready) 5000 battery cycle life at 50% DOD

    5KVA 5Kw Axpert 48v Inverter with built-in MPPT solar charge controller (weight 13.5kg)
    10 KWh Freedom Lite 48v Lithium iron phosphate battery bank. (weight 104 kg)
    (programmable for a 5000 cycle life @ 50% DOD or 3500 cycle life @ 70% DOD
    (Total weight of Inverter & battery bank @ 117.5kg)

    Total cost including installation +- R113000

    (the Lithium iron phosphate batteries are available up to a 2500 KWh battery bank @ R10 Mil)

    Mockup of what the two installations would look like.

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    The inverter feeds a 3 phase DB (with single phase loads) via a 4 pole changeover switch
    Certain loads need to be turned off prior change over to avoid unnessary tripping (All items marked in red)
    Gas geysers will be installed shortly, so that leaves only the underfloor heating (which are permanently turned off), the Jacuzzi, Stove/Oven (Hob is gas) & the swimming pool.
    The upside is that the whole house is powered on inverter mode and have the convenience of turning lights & appliances on in every room in the house.
    (within in the load capacity of the inverter)

    UPS's will be installed in the study & lounge to keep mission critical items on prior the changeover.

    The one concern was whether the three phase earth leakage would trip under earth fault conditions while running on the single phase inverter.

    Tripped at 20ma.

    Three ct's were added for monitoring power consumption either through grid supply or inverter supply.
    This is connected wirelessly to the router and can be monitored via the Efergy engage platform cloud server on a laptop, tablet or smart phone.
    The real time usage is updated every 6 seconds and also gives averages (daily, weekly, monthly & yearly)

    Click image for larger version. 

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    View Demo

    Will be installing an extra CT and transmitter to monitor inverter power seperatley.
    This will give more accurate readings as the grid voltage is +-240v & inverter voltage is +-230v
    Last edited by Tonye; 08-Mar-19 at 04:15 PM.

  2. #2
    Diamond Member Justloadit's Avatar
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    There's no match with respect to cycle times between Lead acid and Lithium.
    The number of cycles stated on the lead are conservative at 400, I found that more like 200 cycles.
    But lets leave it at 400 for the sake of this discussion. One will replace the Lead Acid battery bank 10 times in the same lifespan of the Lithium, and with the advantage that the lithium theoretically could charge in 4 hours, as opposed to Lead acid taking a 24 hour cycle . So lead acid cost x 10 replacements and approximate battery cost of R21K = R210K, against the Lithium cost .

    The question is - Does the customer have the cash up front right now for the Lithium?
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions -

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