New System, Please Advise

jcheil
jcheil Solar Expert Posts: 722 ✭✭✭
in Solar Beginners Corner #1
So I have another neighbor that would like to install an off-grid system.

Based on what I have learned here, I have come up with the following.
Your comments and suggestions are welcome, especially if I am in error in any way.

Daily loads, 3kwh - This will be for 3 days per week, the remaining days, the people will not be there and the fridge (1.2kwh) will be the only thing running. However, in about a 12-18 months, they will be full-time at the location. Largest surge would be either from the fridge or the 3/4hp shallow well pump (filling a tank, then an on-demand pump).

Location, Holopaw, FL, avg 6.74 solar hours per day per PVWATTS. Panels will be mounted facing due south on a 1-axis tracker than can be adjusted 4 times per year (just like mine) .

No need for low-voltage DC nor 240V AC.

They have a 5250w generator, and since they are not going to be there 4 days a week, I would say only 1 day of extra storage would be necessary.

I am leaning towards a 48v system due to the future expansion that will come in the future. Although, it seems to be right at the curve between a 24v and 48v system? Not sure of the best choice. They want to go with the complete outback system, like I just installed. And after all the hassles dealing with other individual components I just can't justify anyone wanting to mess with inferior products any more.

So my calculations are for a 440ah bank @ 48v and 1800w of solar.
Does this seem right? Again, suggestions welcome.
Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: New System, Please Advise

    Let's get the first question out of the way: there is no grid available to the site?

    3 kW hours per day can be done easily on a 24 Volt system. It's really close to 4 kW hours on the DC side, and comes to about 160 Amp hours. At 50% DOD that would be 320 Amp hour battery bank (L16's). Or you could go the GC2 route and have 440 Amp hours going to about 36% DOD. I mention this higher DOD because with the sun during the day you will probably be making better use of panel power and not really bringing the batteries down that deep. What's more, for occasional use (weekends) you could minimize the solar now (and add to it later) running the generator for Bulk before leaving. About 686 Watts of array (round up to nearest available).

    Now about this future expansion. Will it involve increased daily Watt hours or simply more time spent at the location or both? Increased Watt hours would be what tips in favour of a 48 Volt system.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #3
    Re: New System, Please Advise
    Cariboocoot wrote: »
    Let's get the first question out of the way: there is no grid available to the site?

    3 kW hours per day can be done easily on a 24 Volt system. It's really close to 4 kW hours on the DC side, and comes to about 160 Amp hours. At 50% DOD that would be 320 Amp hour battery bank (L16's). Or you could go the GC2 route and have 440 Amp hours going to about 36% DOD. I mention this higher DOD because with the sun during the day you will probably be making better use of panel power and not really bringing the batteries down that deep. What's more, for occasional use (weekends) you could minimize the solar now (and add to it later) running the generator for Bulk before leaving. About 686 Watts of array (round up to nearest available).

    Now about this future expansion. Will it involve increased daily Watt hours or simply more time spent at the location or both? Increased Watt hours would be what tips in favour of a 48 Volt system.

    No grid, it is 1/2 mile from my property which is 6+ miles to the nearest power pole.

    In the future when they are there full time, I expect an increase of 1kwh per day as they would be adding a washer, gas dryer and using more water, lights, tv, etc. I just don't want to paint them into a corner.

    And we will likely go the GC2 route - for the murder set :)
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: New System, Please Advise
    jcheil wrote: »
    No grid, it is 1/2 mile from my property which is 6+ miles to the nearest power pole.

    In the future when they are there full time, I expect an increase of 1kwh per day as they would be adding a washer, gas dryer and using more water, lights, tv, etc. I just don't want to paint them into a corner.

    And we will likely go the GC2 route - for the murder set :)

    Given the expected increase in power needs to 4 kW hours per day I'd say yes, go 48 Volt. Mainly because it's likely to be a larger increase than that once they have the power. People aren't good at keeping their usage down. :D

    In which case at 25% DOD the GC2's would give about 2.4 kW hours for a single string or 4.8 kW hours for two parallel strings. The two strings would need a big array for full-time use: about 2743 Watts.

    And of course there's always the caution about future expansion: the panels you buy today may not be there tomorrow.

    In one way the MidNite Kid helps here, as one is capable of 30 Amps and you can put two together. As such you could start out with a single string of GC2's and one Kid with one array, then later go to two battery strings and add a second array on another Kid and that array could be completely different panels from the first.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #5
    Re: New System, Please Advise
    Cariboocoot wrote: »
    Given the expected increase in power needs to 4 kW hours per day I'd say yes, go 48 Volt. Mainly because it's likely to be a larger increase than that once they have the power. People aren't good at keeping their usage down. :D

    In which case at 25% DOD the GC2's would give about 2.4 kW hours for a single string or 4.8 kW hours for two parallel strings. The two strings would need a big array for full-time use: about 2743 Watts.

    And of course there's always the caution about future expansion: the panels you buy today may not be there tomorrow.

    In one way the MidNite Kid helps here, as one is capable of 30 Amps and you can put two together. As such you could start out with a single string of GC2's and one Kid with one array, then later go to two battery strings and add a second array on another Kid and that array could be completely different panels from the first.

    You are 200% right about people using more because "it exists" :)

    I think I am just going to recommend that they get everything now and we build it as 48v.
    Then they could just use a single FM80 right now and have everything "ready" for when they are there full time.
    Chances are, once they get it, they will end up using it more than anticipated to begin with :)

    And I'd rather keep all the equipment Outback so that there is a single monitoring device for everything (mate3).

    Now, if money was an issue for the short term, what do you think of the feasibility of building the whole 48v system with 2 strings, but without solar for say 3-6 months (until finances come in) and when they are there for the 3 days now, they simply use the generator to charge the batteries each day in the morning for x number of hours, then when they leave for the 4 days, turn everything off.

    Right now they run the generator pretty much 24x7 for the 3 days that they are there now. So in a way they will reduce generator runtime.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: New System, Please Advise

    There are a number of 'part time' cabins that have very limited solar and rely on the gen for bulk charging. This is quite practical, as it avoid investing thousands in PV that isn't used most of the time. The typical plan is enough solar to maintain the batteries when no one is around and enough generator to charge the batteries in a couple of hours per day. It works fine.

    The trouble is always with expanding the solar later: if you plan to put all the panels on one big controller the panels you buy now may not be compatible with the panels you can get later. In fact I ran into exactly this as Sharp stopped building <200 Watt panels so now my four 175's are 'orphans'. Yes, I can figure out how to add new panels - it just isn't as easy as it would have been if I could get the exact same units.

    This is why I suggest the two Kids: price is < $300 or 1/2 a Classic and if you can do with 60 Amps total you spend the same amount of controller and can have two arrays of different panels if need be.

    Keeping all the equipment Outback is not all that advantageous either. It helps when you have multiple charge controllers and inverters, but for one inverter and one (or two) controller(s) it isn't much of a problem. I have OB inverter and controller - but they aren't connected. Still works fine. The only oddity is not sharing RTS for the batteries. But then since the inverter is only used to Bulk charge when the sun doesn't shine a mere Volt or two compensation isn't a big issue.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
    Re: New System, Please Advise
    Cariboocoot wrote: »
    I have OB inverter and controller - but they aren't connected. Still works fine. The only oddity is not sharing RTS for the batteries. But then since the inverter is only used to Bulk charge when the sun doesn't shine a mere Volt or two compensation isn't a big issue.

    In order to share an RTS, you (and I) would need to buy an outback hub. I decided to spend $25 and buy a second RTS... much cheaper than a hub.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #8
    Re: New System, Please Advise
    vtmaps wrote: »
    In order to share an RTS, you (and I) would need to buy an outback hub. I decided to spend $25 and buy a second RTS... much cheaper than a hub.

    --vtMaps

    Maybe it is a new "free" feature but both my FM80 and my VFX3648 each came with a RTS.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: New System, Please Advise
    jcheil wrote: »
    Maybe it is a new "free" feature but both my FM80 and my VFX3648 each came with a RTS.

    Probably, because other companies are including the RTS with their controllers.
    Paid $30 to get mine back in '08 - when the MX60 was $900. I could 'duplicate' mys system for about $2,000 less today and have about 50% more power!
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #10
    Re: New System, Please Advise
    Cariboocoot wrote: »
    Probably, because other companies are including the RTS with their controllers.
    Paid $30 to get mine back in '08 - when the MX60 was $900. I could 'duplicate' mys system for about $2,000 less today and have about 50% more power!

    God don't remind me. In 2005/2006 I paid $5.50 a watt for my original 1000w of panels that I just sold for $900 when I upgraded and bought new GT panels for $0.72 per watt :(
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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