Options when Utility power goes out

I have a 5.2 KW rated solar system on my house with 2 Sunny Boy inverters tied into the local Southern California grid.

Other than an expensive battery bank, what options are there to utilize the power generated by the solar system when the utlity grid goes down, or even out of spec? (Under voltage.)

I know there are issues with using generators, but what about a generator that produces a clean sine wave, such as the Honda EU7000i?

Comments

  • mike95490mike95490 Solar Expert Posts: 8,234 ✭✭✭✭✭
    Re: Options when Utility power goes out

    I found few to none. So Cal, 4.5KW array myself. Best bootleg system I envision was to buy some 400V DC - DC 24V converters, and keep a pair of deep cycle batteries charged to run a pure sine inverter that could handle my 2 fridges daytime, and a couple of lights at night.
    That's why a hybrid system is so expensive.

    The new Xantrex XW series might possibly work for you, as a drop in replacement of your existing inverter. You can build a minimal 48V battery bank with 8, 6V golf cart batteries that will keep a house barely alive for a night, and fully powered daytimes.
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 28,992 admin
    Re: Options when Utility power goes out

    In general, I am a believer that if you have reliable utility power, then a generator is usually a better investment for emergency power...

    However, part of that depends on your local site's issues...

    For example, the last 1 week outage in my area (south of San Francisco, California), was over 50 years ago--the rest have been from a few seconds to a couple hours--generally one or two very short outages a year (seconds) and longer outages (over a few minutes) perhaps every couple years.

    Batteries, even if not used, still need to be replaced every ~5-15--and don't store that much energy for their cost, weight, and size.

    Generators, can be a nice emergency backup--but the larger the unit, the more fuel you would need to store... And, in some cases, like mine, I am really preparing for a major earthquake vs just storm outages--so natural gas, which is a very clean and easy to use source may not be a reliable source in the event of an earthquake (although, up to now--there never has been a wide spread natural gas outage in our area that I know of--other than very rare and localized pipe line failures).

    And, the larger the gen set, the more fuel use becomes and issue... A small Honda eu2000i will keep my emergency power needs going for more than 10-20 days on just twenty gallons of fuel (400 watts for 15 hours at 1.1 gallons per hour--I plan on running ~12 hours per day to keep the fridge, freezer, and a few lights/radio running)... The typical 5kW cheap generator can go through that much fuel in a few days (even with small loads). And, you need to add fuel stabilizer and recycle the fuel once per year--a much bigger issue if you need large amounts of fuel. Then propane may make more sense.

    Also, even the smaller home emergency units like this 12 kW unit, still use 1-2 gallons of propane per hour--10 days of emergency power will require 240-480 gallons of propane.

    If you have/want grid tie solar power... The two major ways of gathering that power are:

    1. to use a system like the Xantrex XW unit which consists of solar charge controllers and integrated Grid Tie / Off Grid inverters with transfer switches...

    2. using your current Grid Tied inverter system and a standard sine wave inverter. You can actually back drive an Off Grid inverter with a Grid Tie inverter and charge your battery banks. There are some newer solutions just out there that will integrate battery charging control into this type of system--but I do not know enough to recommend any setups yet. If not done correctly, you can severely overcharge and damage your battery bank.

    Perhaps Solar Guppy (or others) can recommend some equipment manufacturer(s) and model numbers that can be put together to support the #2 type system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Options when Utility power goes out

    My "backup" is a Xantrex XW-6048. My Gridtie is 12kW of PV into 3 GT inverters, a pair of Xantrex GT5.0's and a GT3.3. Last weekend, I ran a "hurriance check" and took the whole house 100% offgrid and used the GT's as inverter/chargers ( they sync to the XW-6048's output )

    I have a "emergency" cross-connect breaker that connects the Output of the XW-6048 to the main panel, default configuration, the XW-6048 powers only the homes AC. The cross connect is very simple as the XW-6048 is split phase. All that is needed is to open the input breaker to the XW, trip the houses main 200 amp breaker and engage the cross-over breaker ( ties the XW-6048 to the main panel and hence the GT's outputs ). 5 minutes later the GT's came online and I was running the AC, the pool pump and all the loads in the house AND putting about 50 amps into the battery bank ( 440ah @ 48V ). With the GT's having a peak available of about 10kW AC and the XW-6048's 6kW AC, I can run all day long this way and fully charge that battery bank, which is enough to run the AC and basic house loads ( plama TV, Computers and refrig ) all night. The only issue I had was when the AC kicked in, it would trip offline the GT's, no big deal, they come back online by themselfs 5 minutes later

    In theory, I can go forever like this if the Grid gets wacked by a big storm ( IE hurriance ) and still use everything in the house with NO generators or need to store fuel, just need sunny days and this is without using charge controllers

    Only thing I have to watch is the battery voltage and the main breaker to the house MUST be tripped, which are manually operations. This could be improved saftey wise as its NOT a good thing to have a offgrid inverter backfeeding, but this is only for emergencys when the grids toast. Normally, the XW-6048 powers the AC and the Outback FX-3048 powers the office, living room and kitchen with auto transfer relays built into the inverters

    While not automated, it does allows fully use of the PV and the kW's from the GT's should the need arise without the need for High voltage charge controllers. It also gives a signifigant increase in what loads can be driven as the GT's are more than 2X the AC watts than the XW-6048 is and they load share, something a charge controller only settup can't do.

    Costwise, the XW-6048 and batterys are about 6K, considering the flexibility and no fuel and allowing the use of the GT PV without the grid I feel its a good option for the technically aware home owners.
  • BB.BB. Super Moderators, Administrators Posts: 28,992 admin
    Re: Options when Utility power goes out

    Solar Guppy,

    Question; what happens when 10+kW of GT hits 6 kW of inverter?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Options when Utility power goes out

    Not sure BB, I keep the loads high enough so thats not an issue for this emergency setup. In the Summer my GT AC peaks about 8.8kW, I also have split arrays, half face south east the other south west which keeps the peaks down but the average higher
  • System2System2 Posts: 6,290 admin
    Re: Options when Utility power goes out
    BB. wrote: »
    In general, I am a believer that if you have reliable utility power, then a generator is usually a better investment for emergency power...

    -Bill

    I do have a Honda EU6500is Generator that I have converted to propane and have several tanks (2 100 lbs and 2 60 lbs and 4 20 lbs) on hand that will allow me to run the generator for 4 days straight if needed. (Freezers and shed power at night and house during the day.)
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Options when Utility power goes out
    jst3751 wrote: »
    I do have a Honda EU6500is Generator that I have converted to propane and have several tanks (2 100 lbs and 2 60 lbs and 4 20 lbs) on hand that will allow me to run the generator for 4 days straight if needed. (Freezers and shed power at night and house during the day.)

    If you don't mind sharing, what was the cost for this backup solution? I assume this is 6.5kW so its very compariable to my added backup with the XW-6048. Thanks!
  • System2System2 Posts: 6,290 admin
    Re: Options when Utility power goes out
    If you don't mind sharing, what was the cost for this backup solution? I assume this is 6.5kW so its very compariable to my added backup with the XW-6048. Thanks!

    I believe the cost of the generator including shipping was $3100.
    The cost of the convesion kit was about $150.
    I would say the 4 new tanks (2 60lb and 2 100 lb) totals about $350
    Add about another 75 for hoses and fittings.

    Add about $350 for cords and my home built distrubution box.
  • BrockBrock Solar Expert Posts: 632 ✭✭✭✭
    Re: Options when Utility power goes out

    Solar Guppy apparently the GT inverters land in your main panel or down stream of it anyway? I have been told we would have to add a second separate utility meter with any GT inverter(s) which would prevent us from being able to do this without some major cross wiring. This is the biggest reason I went with a XW and 200 amp sub panel and told them I am only powering loads downstream of the inverter.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Options when Utility power goes out

    Yes. the GT's are off of breakers in the main 200 amp panel, We have a single meter, that is electronic that measures seperately enegry in each direction. This is done by Lakeland Electric so that there are no negative readings which breaks the billing process, IE house comsumption is billed on on register and solar over net is giving as a credit on the other. Close to net metering but no quite due to how taxes are dealt with
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