Grid tie system with Solar and Lithium pack

kyferez Registered Users Posts: 3
I am in the process of planning. I intend to start with 48kWHr of lithium batteries modules, and add quite a bit more if it preforms as I think it will.

I have been researching, and my desired plan seems sort of complex and I've not found much info on how to accomplish what I want to do, so I will explain my goals below and hope I'm clear and someone can guide me to how I can accomplish this and what I'll need. I am an electronic engineer and fully understand power voltage etc. The complexity comes in the "features" I'm looking for with the electronics involved.

Basically my goal is to "buffer" electricity using lithium batteries as I have access to very low cost ($0.01 / kWHr) electricity during off-peak hours, so want to leverage that with solar using batteries to eventually eliminate daytime Grid usage. Additionally I mine cryptocurrency so reducing electric usage is highly advantageous.

What I envision:
1) Grid meter 1 with regular price electric---->Powers house during day if batteries are drained

2) Grid meter 2 with low cost Electric at night(very high cost during day)--->Powers battery chargers ONLY at night per programmed schedule

3) Batteries--->Generate power for house until discharged.

4) Solar--->Charge batteries and feed Grid meter 1 during day

So it's sort of complex, and I am having trouble finding out what I need to accomplish a system like this. I would like a system that is expandable so when I add batteries I can add capacity.

My main point of not understanding is what equipment is required to do the above 4 points with up-gradable capacity up to 200kWHr as I add components.

Other details: At peak usage, I pull 100kWHr per day. Grid Meter 1 circuit is 220VAC 200Amp residential in the US. I'm waiting on additional details for Grid meter 2 from power company.

Thank you for any help!


  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Most residential installs are simple, till you reach 10Kw installed PV.  Then the permitting and connection get tricky, you may want to look into what rules are in your neighborhood before you go too far.
    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

    gen: ,

  • kyferez
    kyferez Registered Users Posts: 3
    edited June 2018 #3
    I am going to have some limits with the solar. The solar is an addition in the idea; the primary goal is actually to "buffer" the cheap electrical using the batteries in order to save cost, over time.

    What I am looking for is recommendations on the electrical equipment to provide the features I detailed in 1-4.
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    So if I'm understanding this properly, it seems like you want a grid-tied inverter that can preferentially use solar/battery rather than grid, on service/meter 1. I'm not a grid-tie person, but that doesn't seem too complex to me.

    For service/meter 2, you basically want a battery charger controlled by time-of-day. Also doesn't seem all that complex.

    That said, when you're getting into bigger, higher voltage and/or higher current DC systems, you're likely to need some help from someone who knows what they're doing.
    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
  • kyferez
    kyferez Registered Users Posts: 3
    When you put it that way, I guess that does simplify the whole thing :) The only other difficulty then is figuring out what units can do this and be stack-able to increase capacity as I increase battery storage.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    Look at Schneider and Outback. 48 Kwh is not that big and I have been involved in much larger. What you want is really a combination of both of the links below. Good Luck!

    "we go where power lines don't" Sierra Nevada mountain area

  • MarkC
    MarkC Solar Expert Posts: 212 ✭✭✭
    Have you discussed this with a Pika Energy representative?  They make off-shelf systems that might actually accomplish your goals - with warrantied equipment/installations.  I certainly would like to know if they can do this as I'm considering such a system based on a "free night" electricity plan that is available to me.  However, you will need to buy their (expensive) smart battery systems - which for the storage that you are considering might be unaffordable!  It's a great idea if you can make a solar/energy storage system pay for itself based on cheap off-peak energy costs.
    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.