BlackHoleSun_TN: Genset to Solar off grid migration questions

This discussion was created from comments split from: Off Grid Refrigerator/Gas Stove recommendations for 2018?.

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  • BlackHoleSun_TNBlackHoleSun_TN Registered Users Posts: 8 ✭✭

    Thank you all! I see now that Propane refrigeration may be a bit costly upfront with a lot of concessions for safety and longevity. Even with the summer cost of propane being about $2.40/gal propane fridge/freeze may not be the best option.

    To Dave Angelini:

    More detail - Current state; I Iive, full time, in two cabins, soon to be three, powered SOLELY by MEP-802a Diesel Genset (5kw-8Kw Primary) and Backup MEP-002a (5Kw-8Kw) diesel generators.

    FUTURE state: to build out about a 8Kw Solar Field with Mission solar panels (14x 360 MONO) and use TIGO optimizers with a Schneider Electric XW+ 5548 Inverter, Schneider Electric MPPT80 Charge Controller connected to 48v LiPO batteries(14Kw; 4x 3.5Kw SimplPhi batts in parallel (proposed))

    Biggest Concern: 1) Continuous refrigeration and freeze of perishable goods, 2) overnight lighting (LED), 3) shallow well water pump from holding tank to pressure tank.

    In this situation;

    1) will the EnergyStar Fridge startup be too hard on the Batteries overnight and deplete them?

    2) Would Propane Refrigeration/Freezing for a family of 7 be too costly (based on the responses, I assume so)

    3) Should I look at changing my system plan to accommodate two energy star appliances (approx 500Kw/yr from Best Buy)?

    4) Suggestions?


    Thank you from the Idiot Child.

  • BB.BB. Super Moderators, Administrators Posts: 29,811 admin

    BlackHoleSun_TN,

    I have split your post to its own thread. That way we can focus on your needs and questions.

    So, just continue your discussion here.

    My questions--Where is the system located (so we can estimate how many hours of sun per day you get).

    And have you measured your present power usage? Watt*Hours or kWH per day / per month / by season?

    A refrigerator generally needs around a 1,200 to 1,500 Watt AC inverter to start/run reliably. That is around a 600-700 AH @ 24 volt (flooded cell lead acid) battery bank (and will run LED lighting, a washing machine, laptop computer, LED TV, a "solar friendly" well pump... (suggest around 3,300 WH or 3.3 kWH per day is a good single cabin/small/energy efficient home.

    When you have multiple cabins/homes/refrigerator+freezers/etc... The systems get pretty large and have no problem starting a residential refer/freezer.

    Typically a full size energy star refrigerator (USA full size fridge/freezer) usually runs around 1.5 to 2.0 kWH per day... A family of 7 may have 2x refrigerators and 1x full size chest freezer (my guess).

    You are talking about a relatively large system -- Something like 4-6 kWatt AC battery bank (and a 400-600+ AH @ 48 volt battery bank).

    If you plan on 2 days storage and 50% maximum discharge (a good optimum for typical off grid home), that would run around:

    • 600 AH * 48 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 6,120 WH per day (6.12 kWH)

    And a 600 AH @ 48 volt FLA battery bank would support ~3,000 to 6,000 Watt AC inverter nicely.

    Using the http://www.solarelectricityhandbook.com/solar-irradiance.html website for Nashville Tn (if that is near where you live), fixed array, faciing south, tilted to 54 degrees from vertical, we see ~2.87 (DEC) to 5.22 (JUL) hours of sun per day.

    For 9 months of the year you get >4 hours of sun per day. The size of array needed to "break even" on 4.0 hours of sun would be:

    • 6,120 WH per day * 1/0.52 off grid AC system eff * 1/4.0 hours of sun = 2942 Watt array "break even" @ 4 hours of sun

    And to charge the battery bank, you need 5% to 13% typically for charging FLA battery bank. And for full time off grid, highly suggest 10%+ rate of charge. To calculate:

    • 600 AH * 59 volts charging * 1/0.77 solar panel+controller deratings * 0.10 rate of charge = 4,597 Watt array "nominal" suggested

    So, while you might get away with 2,942 Watt array, rounding up to 4,597 Watt array will be better for the battery bank, and let you reduce genset runtime in the winter. For example, 4 hours of sun would supply:

    • 4,597 Watt array * 0.52 off grid AC system eff * 4.0 hours of sun = 9,562 Watt*Hours per average "sunny" day minimum for ~9+ months of the year.

    Anyway--More of a suggested starting point. And how you would "do the math".

    And, another option is to build a "solar power system" for your minimum "base loads", and use the genset to power heavier loads (shop tools, cooking, large amounts of water pumping, etc.) during part of the day, or when necessary.

    Your thoughts/corrections to my guesses?

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,494 ✭✭✭✭✭

    If you are building a PV array in a field, you likely do not need the optimizers, since it's not on a house that requires rapid shutdown.

    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 ,

  • Dave AngeliniDave Angelini Solar Expert Posts: 4,859 ✭✭✭✭✭

    TN is Tennessee ?

    Hey Bill, can't you moderate to where he is? The new software won't?

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 29,811 admin

    No... It looks like he may have posted from his cell phone. Ip Locators give multiple US wide results for these and other "large shared" ISPs (VPNs, server farms, large companies, cell phone companies)--They aggregate users from a large region and have "one" IP exit point.

    I just guessed that "TN" was Tennessee.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,859 ✭✭✭✭✭
    edited March 6 #7

    Interesting! Hide in plain sight.

    I just turned on the AM and hear the lightning coming. YUK better go....

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BlackHoleSun_TNBlackHoleSun_TN Registered Users Posts: 8 ✭✭

    Thank you SO VERY MUCH BB.

    All of the calculations are very helpful, and I'm able to plug the numbers of what I'm looking at installing.

    I'm Looking at the Optimizers because there are a couple of hardwood trees I'd like to keep and at certain times of the day in Spring & Summer, the top branches may shade the end two panels in the field I'm looking at building this in.

    Also, How far can my solar array extend with these optimizers?

    The numbers you listed are for FLA batteries, any experience with the newer LiPO which claims 80% to 100% DoD? I like them because I can continue to add 48v (80AH) Units as I see fit. Goal is 10 of them, but at about $3,300ea. it's a muti-year budgeted expense!

    Also, suggestions on sizing for the Schneider Electric MPPT 80? Will I need two with 14 360W panels? Suggestions?

    Loads:

    I am building the homestead around efficiency first comfort 2nd or 3rd; Just me & Kids, so no objections ;-0)

    Heaviest Load would be the deep nwell pump at 11.8A rms, and about 22A startup. I will probably run this once every other day into a storage tank (i do this now on genset).

    2nd heaviest is shallow well pump to pressure tank; about 9A startup, 4-6 rms - runs several times per day.

    3rd Mini-Split AC unit with DC motor condenser; only run from June-Sept - probably full genset

    Proposed: Thinking of a dishwasher... but then, what would the kids do?

    All other AC Loads: Laptops, 1xPlaystation, couple LCD TV/Monitors, Washing machine, Propane Dryer, Propane Stove, 4-5 Ceiling Fans (DC Motors), REFRIGERATOR, FREEZER, Rinnai Tankless LP Water Heater, LCD Lights around property. NO MICROWAVE... food doesn't even taste right with them.

    That's all i can think of now.


    Thank you all for your guidance!... and lots of numbers.

  • mcgivormcgivor Solar Expert Posts: 3,202 ✭✭✭✭✭

    I'm Looking at the Optimizers because there are a couple of hardwood trees I'd like to keep and at certain times of the day in Spring & Summer, the top branches may shade the end two panels in the field I'm looking at building this in.

    What time of day is the shading,, early morning or evening my make little difference. What is the distance between the array and controller location.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • EstragonEstragon Registered Users Posts: 4,286 ✭✭✭✭✭

    If there's some shade in spring/summer, what happens in fall/winter?

    Off-grid.  
    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
  • mike95490mike95490 Solar Expert Posts: 8,494 ✭✭✭✭✭

    Dishwashers are for sunny days after batteries have been in absorb for an hour

    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 ,

  • BlackHoleSun_TNBlackHoleSun_TN Registered Users Posts: 8 ✭✭

    McGivor -- Tree shading will be early morning, panels would have full sunlight by 10am in summer and 11am in winter.

    Estragon -- It's hard to say Fall/Winter; but since leaves are gone, the branches could shade a bit, but not much after 11am

    Mike95490 -- I would run the dishwasher, as well as washing machine, and deep well pump all on genset; Idea is that in the evenings I would run the genset for a couple hours to top off water storage tank from deepwell pump, people can take showers, I could run a load of dishes, and a load of laundry, as well as charge batteries for 2-3hrs before shutting it down. That way all heavy loads are out of the way, and batteries are fully capable of handling all overnight loads. Since looking at LiPO, Batts, I can use them in any state of charge, so the genset schedule would be beneficial all the way around.

    At least that's my opinion... i could need shock therapy.

  • mike95490mike95490 Solar Expert Posts: 8,494 ✭✭✭✭✭

    It's your choice, you will need a generator for long periods of bad weather.

    > 8Kw Solar Field with Mission solar panels (14x 360 MONO) and use TIGO optimizers with a Schneider  MPPT80

    Is that a valid configuration, optimizers with Schneider  MPPT80 ?

    You may also want to consider using a smaller inverter genset instead of all diesels, can use a lot less fuel.

    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 ,

  • mcgivormcgivor Solar Expert Posts: 3,202 ✭✭✭✭✭

    Since the shading is before the meaningful sun, it probably wouldn't make much difference with or without optimizers, it's the critical time 2 hours before and after high noon that are the most important.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • EstragonEstragon Registered Users Posts: 4,286 ✭✭✭✭✭

    You might want to use numbers like these for solar elevation and azimuth in spring/summer vs fall/winter.

    For Nashville, optimal angle (from vertical) varies from 30° in Dec to 78° in June. In Dec, azimuth varies ~20° either side of south, vs 110° in June. With these angles, and a simple protractor, you can get a pretty good idea of what shading will look like.

    As Mcgivor said, early/latesun is marginal anyway. At 30° though, shadows are pretty long. If there are trees likely to shade more or less due south of the array you may want to reconsider location or take out some trees. Even bare branches can reduce output to near nil, even with optimizers.

    Off-grid.  
    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
  • BB.BB. Super Moderators, Administrators Posts: 29,811 admin

    And trees grow... In another 10 years, you might be in deep shade every day.

    Any place you can install the array without heavy shading year round? With a high voltage array and high voltage MPPT charge controller, you can put them several hundreds of feet "somewhere else".

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BlackHoleSun_TNBlackHoleSun_TN Registered Users Posts: 8 ✭✭


    And we've had LONG periods of bad weather this year... 3-4 days of straight rain!

    I was told I would need a charge controller with the Optimizers. Not sure how MANY charge controllers I'll need... still trying to figure out that calculation.

    For longevity, the 2cyl. Diesel Genset at 1800 rpm only burns .26 gal per hr at idle, and .40 gal per hr at 80%+ not sure if I need another Inverter Genset. What is your suggestion?

  • BlackHoleSun_TNBlackHoleSun_TN Registered Users Posts: 8 ✭✭

    in short... cut the trees whilst I still can, make sure there's a clear path for sun!

    may have to do that, and just forget the optimizers... sounds like the expense isn't justified.

    Do they make anything else about setting up the system easier?

  • Dave AngeliniDave Angelini Solar Expert Posts: 4,859 ✭✭✭✭✭

    Optimizers are fluff for Offgrid. A decent quality build of electronics from the same manufacturer like Outback, Schneider, or even Magnum will tell you all you need to know. They are fluff because we don't have shading from trees. We cut down the ones that are shading always offgrid. If you can't cut a favorite tree then add a second array on its own controller that solves the shading from the first array. Good Luck!

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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