46 kW solar battery based system with grid back-up

thorbjornwthorbjornw Registered Users Posts: 14 ✭✭
I am putting a solar system together for our hotel in Nicaragua, where electricity is expensive (21 cents/kW) and there is no feed-in tariff. As most of our energy consumption is at night (70%), the batteries are the core of the system. I have ordered a 144 kWh Ni-Fe battery bank and 170 Yingly 280W panels in China, and am now looking for at setup for inverters and solar chargers.
Our system here is 120/240 split phase, and our load is between 4 and 20 kW.
My idea is to order 6 Schneider XW+ 6848 inverters, 3 Power Distribution Panels and 9 XW+ 80-600 chargers to make 3 blocks of dual inverters in parallel.
The whole idea is to be as grid-independent as possible, charging the batteries each day and discharging them in the night, and only use the grid when the batteries are down to 20% SOC, probably in the late night or early morning hours.
My doubt is whether this will work without a transfer switch, as the information in the Schneider documentation is difficult to understand. They state that the risk with not using a transfer switch is that the last inverter to open will have to handle the overall load current, so if a higher current rating is needed than the internal pass-through capacity of 60 Amp (and I will need that) then it is necessary to use either an external contactor or a transfer switch. But then I understand that it will not be possible to configure a system with an external transfer for load-shaving (selfconsumption) - not sure why that is so.


  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    Sorry i wont be answering the technical questions you asked.  You're looking at a very large system.  I will let more advanced people answer them. I don't think your offgrid system is going to produce energy more cheaply.  But I would work on conservation which I know is super hard in a hotel setting.

    But I would imagine main consumption is air conditioning. 
    Have you been up on your roof recently.  It should be painted bright white to reflect solar energy. Especially if it is a concrete roof without insulation.
    I am in mexico and some roofs turn dark, alost black. Makes the structures roast.
    Insulating shades for the air conditioned spaces. Awning type structures to keep sun off the windows. 

    Do you have solar hot water heating system?Super cheap here in mexico (comparatively).

    Since you already have it bought I would use solar energy to offset daytime usage . Then what ever you can get into your batteries can help at night. But not go crazy about night time usage ni-fe batteries are not terribly efficient.  So basically use all the power you can during sunny hours. This way less needs to discharge and charge batteries.  

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    I think you should be looking into FLOW batteries, a commercial product...  to start try RED FLOW in Australia...http://redflow.com/

    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
  • jonrjonr Solar Expert Posts: 1,379 ✭✭✭✭
    If it is for AC, then I'd look into thermal storage (ie, water tanks) along with something like Chiltrix heat pumps - running mostly while the sun shines.   And I second the suggestions about making the place need less (insulation, air sealing, more efficient heat pumps, etc).

    I am available for custom hardware/firmware development

  • cupcakecupcake Solar Expert Posts: 254 ✭✭✭
    21 cenes per kwH is WAY CHEAPER than any solar setup is going to be...

    Stay on the grid is 'savings' is your goal -- not gonna happen with solar....
    The point of solar is to live in remote, beautiful places where the grid doesn't reach and have a decent amount of electrical power

    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired

  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    edited November 2016 #6
    That 21 cents a kwh, does that include delivery fees? Thermal storage would have to be huge but it is a good idea, as water does wear out like batteries do. The battery cost alone is going to be huge!

    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
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