Maximum output of an off grid system!

icarus
icarus Solar Expert Posts: 5,436 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
We have been having a string of rather unusual weather this week, and it is expected to to continue for the next week at least. Night time temps ~ -10-20 F with daily highs in the low 20's F. with absolutely crystal clear days with no clouds at all,, from sun up to sun set, very low humidity.

As an interesting test, I decided to see what the absolute maximum harvest I could get out of my system. System details in my signature. So yesterday, I tried to drive the batteries down as much as I could reasonably do in one day. I ran them down last night running both paddle fans on max, and the bed warmers for over an hour, so by morning I was down ~ 20%, or 90 ah. Battery voltage this morning was ~ 12.5 vdc.

So, with great reflection off the snow, with the extra 90 watt panel set up on the ice moving through out the day to follow the sun as best I could here is what happened. I wanted to make sure that the Rogue controller never left bulk charge so that it would not dial back out put, so I turned on nearly everything I could during the day.

The sun comes on the panels right at sunrise, ~ 7:15 AM, and by 8:00 they were putting out ~ 20 amps. By 2:00 Pm the sun is off the main house panels, but the Sun 90 on the ice continues to get full sun until ~ 3:30. At this time of year, I continue to harvest ~ 50 watts until nearly 5:00 Pm just off the reflection off the lake ice and snow.


So here is the bottom line. I was able to harvest 2.14 kwh, or 156 ah (12 vdc) (Actually a few more since it still hasn't shut down completely. I was seeing MPPT advantage early in the day of better than 30%. I saw a peak of 381 watts, (from 412 nameplate installed) The highest current I saw (the Rogue doesn't log peak current) was just under 29 amps.

This all translates to ~ 5 times the name plate rating of the system. It is probably the absolute best you can get near the equinox anywhere on the planet. Cool panel temps helped (afternoon panel temps read by ir ~ 50F)

The weather is likely to be the same tomorrow. I will go back to my normal, 5-800 wh of load, knowing that under ideal conditions I can get better than 5 times name plate!
I still stand by my rule of thumb calc, name plate/2*4=average out put of an off grid system.

Tony
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Maximum output of an off grid system!

    Now that's harvest! :D

    It's already above freezing in the Cariboo. If I were to get readings for our coldest days ... well there's only 6 hours of sun total so it probably wouldn't be much.

    Besides, I'm not trudging for three hours through waist-high snow to get to the cabin. :p

    Going to have to install some sort of solar electric at the new house just to play with it!
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Re: Maximum output of an off grid system!
    Cariboocoot wrote: »
    Now that's well there's only 6 hours of sun total so it probably wouldn't be much.

    I didn't do much astro physics... but, we're half way between winter solstis and summer? Shouldn't just about every one be close to 12 hours a day?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Maximum output of an off grid system!

    Read it carefully.

    The coldest days are mid Winter. Only about 6 hours long total at 53 degrees Lat.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #5
    Re: Maximum output of an off grid system!

    It sure was a productive day today. My house system harvested 10.1kwhrs from my 2.1kw of pv. That was not using the full capability either. The little distiller (water for the batteries) ran for many hours, but with it and charging the system still wasn't taxed to the max. I think I could maybe get over 11kwhrs, but that would be a lot of dancing with heaters and watching the MX60 to make sure I was maxing it.

    Today's production on the 10kw microFIT hit 85kwhrs for the first time. Gotta love those cold clear days!

    Ralph
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
    Re: Maximum output of an off grid system!
    Ralph Day wrote: »
    ... The little distiller (water for the batteries) ran for many hours,....

    What do you use for a distiller ??
    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 ,

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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #7
    Re: Maximum output of an off grid system!

    Hi Mike
    It's a little old Sears gallon in gallon out unit. (20+ years old at least). The top with the fan lifts off, you pour in a gallon of water, put the top back on and plug it in. Auto shut off when done. It's a great little dump load. To prevent cycling on and off too quickly I have a ''hold'' of 5 seconds on the diversion setting on the MX60.

    Ralph
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    Re: Maximum output of an off grid system!

    When we are talking about "Hours of Sun"--We are really assuming 12 hours of sun (all angles, average weather) are gathered and then divided by the Noontime sun (1,000 Watt*Hours/square meter).

    So "6 Hours of Sun" is not literately, 9am to 3pm sun... It is all light energy from 7 am to 7 pm integrated together equivalent divided by solar noon sun to 6 hours of full 1,000 WH / sqmtr sun.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Maximum output of an off grid system!
    BB. wrote: »
    When we are talking about "Hours of Sun"--We are really assuming 12 hours of sun (all angles, average weather) are gathered and then divided by the Noontime sun (1,000 Watt*Hours/square meter).

    So "6 Hours of Sun" is not literately, 9am to 3pm sun... It is all light energy from 7 am to 7 pm integrated together equivalent divided by solar noon sun to 6 hours of full 1,000 WH / sqmtr sun.

    -Bill

    Uh, when I talk about "6 hours of sun" in Cariboo Winter I mean six hours total. Yeah, sun up at 9:00 and back down again by 3:00 PM! :cry:

    Another thing to consider is that even with our outrageously long (16 hours) Summer days you won't get much more than 5-6 hours "equivalent good sun" on fixed mount panels, as for much of that time the angle is too far off to produce any solid power.

    But if you have a tracker .... :D
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #10
    Re: Maximum output of an off grid system!
    Cariboocoot wrote: »
    Uh, when I talk about "6 hours of sun" in Cariboo Winter I mean six hours total. Yeah, sun up at 9:00 and back down again by 3:00 PM! :cry:

    Another thing to consider is that even with our outrageously long (16 hours) Summer days you won't get much more than 5-6 hours "equivalent good sun" on fixed mount panels, as for much of that time the angle is too far off to produce any solid power.

    But if you have a tracker .... :D

    Trackers are cool!

    My trackers trade off max energy collection for simplicity, so I lose an hour or so of collection a day.
    Still, this time of year I'm getting close to 10hrs worth of AC nameplate production a day (on clear days)
    A couple days ago I hit 28.2 kwh
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  • SteveK
    SteveK Solar Expert Posts: 387 ✭✭
    #11
    Re: Maximum output of an off grid system!

    I've noticed the same here. Record gathering in our home. Five beautiful days here back to back and I'm running my Nyle heat pump water heater directly off the solar. Keeping my freezer and stoker on it as well.

    5.1 KWH best day so far off 1080W nameplate. Doesn't start breaking 8A till after 10:00. Heavy shading in the morning...I've seen the Classic suck 45A briefly from these panels.

    Maybe this solar stuff does work after all?
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