Opinions

Options
notes
notes Solar Expert Posts: 52 ✭✭
I just got back from opening up cabin in Upper Michigan. Used a kilowatt meter on all loads, great investment. Had to make a few cables for devices that are not plugged in. We came up with 2891 watt hours for the highest day of 4 days. I talked with a contractor and this is what he is recommending. We are off grid, no grid for miles. Magnum MS4024PAE with MMP power panel, ME-ARC control, ME-AGS-N auto gen start, 12 L16,6volt,380 ah. 3 Kyocera 245 watt modules, FM60 charge regulator, top of pole mount, pole and all cables, for 1200ah batteries and 735 watt solar array. Currently using 5 kW onan generator. Any input appreciated.
Andy
4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
Off grid in Upper peninsula Michigan
«1

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Opinions

    Shall we do the math?

    2891 Watt hours is close enough to 3kW hours. That's AC, not DC. Factor in the conversion and you've got about 3333 Watt hours. Add full inverter consumption and the number goes up to 3813, which is pretty close to 4kW hours.

    Obviously the first idea is to see if you can knock the usage down, and/or plan on some of those loads being run generator only. Any possibilities?

    Otherwise you're looking at using just under 166 Amp hours @ 24 Volts. Go to 48 and you cut that down to 83. That means the 24 Volt battery bank would only need to be 664 Amp hours, not 1140.

    The idea of twelve L16's is a bad one. For 24 Volts that means three parallel battery strings which is something you should try to avoid. With 380 Amp hour batteries that's 1140 Amp hours. A single FM60 charge controller can not pass enough current to charge that. The three 245 Watt panels (735 Watts) would not produce enough current to wiggle that much battery, much less charge it. Maybe 24 Amps. (My array is slightly smaller and produces just a tad less than that).

    So right away we know your contractor doesn't know what he's talking about and you'd be in for some very dead expensive batteries quite quickly unless you want to run that Onan a lot.

    To give you an idea, in order to get that 3kW hours AC we'd expect an array around 1440 Watts and a battery bank of 450-500 Amp hours @ 24 Volts.
  • 11JAGAN
    11JAGAN Solar Expert Posts: 34 ✭✭
    Options
    Re: Opinions

    To give you an idea, in order to get that 3kW hours AC we'd expect an array around 1440 Watts and a battery bank of 450-500 Amp hours @ 24 Volts.

    cariboocoot,

    i am ok with your battery bank size(@25% DOD)
    but how u calculated the panel size
    normally it should be
    =(450 x 24) x 0.25 / 5
    =540/.77
    =700watts

    pls xplain
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Options
    Re: Opinions

    You are indeed lucky... you asked before you spent. And you got very good news from Cariboocoot, in particular that you are proposing to spend too much on batteries and not enough on solar panels. The reason that is such good news is because batteries are a lousy investment and solar panels are a great investment.

    It seems you have almost taken the first step: determine your load. You didn't mention your peak load, nor did you mention the type of load. This is important because, for example, a vacuum that draws 1200 watts may have poor power factor and require 1800 watts (or more) of inverter capacity. Startup surges (pumps, fridges, power tools, laundry) are notorious for swamping inverters (and generators) that nominally have adequate capacity.

    There's another aspect to the load: time of use. This relates to your lifestyle. For example, if you only do laundry or vacuum on sunny afternoons, that means you do not need to store that energy in your batteries.

    You are about to take the second step in designing a system: choose a battery and a system voltage. This is far and away the most difficult part of designing a system. AFTER you choose a battery bank, you can start to size your solar array and choose a controller and inverter.

    The system voltage depends on many factors.
    Peak continuous load: the more watts you draw at one moment, the higher the system voltage needs to be.
    power production: The size of your array depends primarily on your battery (which you need to choose BEFORE you determine your array), but generally the larger your array the higher your system voltage should be.
    Distance: How far apart are your panels from the batteries and electronics? The further apart they are, the more advantageous to bump up the system voltage.
    future expansion plans?: higher voltage.

    Choosing a battery is more than difficult. And it can be circular because your system voltage may depend on your battery, and your battery may depend on the system voltage.

    example: let's say you determine that you need a 20 kwh battery bank. Let's say you want to use L16 batteries. You therefore need 8 of these batteries. You can do two parallel strings of 4 batteries (24 volt system) or one string of 8 batteries (48 volt). A single string of batteries is best design practice, but you need to weigh the advantages of a 24 volt system against that.

    One thing in favor of lower voltage is battery maintenance. In the above example you were constrained by the need to use L16 batteries. If you were to use bigger batteries, you could have a single string at 24 volts. At any given voltage, a single string of batteries is easier to maintain and has fewer points of failure.

    There's a lot to be said for starting out with cheap batteries (mass produced, like golf cart or floor scrubber batteries), and then moving on to bigger and better batteries after you murder the cheap ones. For example, start out with two strings of golf cart batteries in parallel (440 ah), and then upgrade in a few years to a single string of 450 ah (or larger, if your loads have grown) batteries. The larger batteries tend to be more expensive per kwh of storage, but they can last longer than the cheap batteries and may be more cost effective in the long run.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Options
    Re: Opinions
    11JAGAN wrote: »
    i am ok with your battery bank size(@25% DOD)
    but how u calculated the panel size
    normally it should be
    =(450 x 24) x 0.25 / 5
    =540/.77
    =700watts

    pls xplain

    I think Cariboocoot recommends that a 450 ah battery bank should have 45 amps charging current.

    45 amps at 24 volts is 1080 watts. If you derate the production to 75%, 1080 watts into the batteries requires 1440 watts of panel.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Thanks for the reply's. I am at work, I will try to answer some of the questions when I get home tonight. Boy, I thought this guy knew what he was doing. Must be why he wanted me to buy a 8kw generator from him also.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Options
    Re: Opinions

    Do not spend any money until you do a couple paper designs and cost the system(s) first.

    There are tradeoffs on any of these decisions. And none of these decisions can be intelligently made until you a) know your loads or b) make a guess and design the system to support that requirement--Understanding that you will need to adjust your actual usage so that they work with the design selected/implemented.

    In general--You can "cost effectively" size an off grid system by approximately a factor of 2x larger (or smaller). If you are off by more than that--Generally you just about have to start from scratch. For many reasons, most of the hardware/wiring is easily migrated between old and new systems.

    And, it does not mean that you cannot start with a "small" system (1-3.3 kWH per day) with some more generator run-time (when needed), and a few years down the road moving there full time and building out a new system for 10+ kWH per day (a pretty big system for off grid).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Thanks for all the info. I will try to explain how I came up with usage. Forgive my lack of knowledge in solar as I am learning each day. If this was heating or air conditioning that would be a different story. We opened up cabin for three days, we measured voltages, watts with kilowatt meter and amps on water pump. We then timed everything we could for usage. I then entered all data into Wind & Sun load analysis. That program using three days per week gave totals of 1221 average watt hours per day and 2891 maximum watts per day. I did have to guess on some of the devices for times in summer like ceiling fans and such. No fridge, washer, dryer. Highest usage was TV and two ceiling fans. TV usage has to change. We can listen to radio. Well pump is 230 volt. No plans on living permanently at cabin, no access in winter. Usually three day weekends and a week here and there. Distance from equipment closet and solar array is 75' future plans? lights in garage. We run all our power tools from gas generator, separate from cabins. I ran outlets on all sides of cabin and in garage and when I need power outside just start up the little Honda.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Options
    Re: Opinions

    Way too many batteries for he loads, and way not enough PV for those batteries.

    As a comparison, we use 500-800 WH/day, provided by 400 watts of PV, into 450 ah of batteries. My rule of thumb is, take the name plate rating of the the PV, divide by 2 to account for all cumulative system loses, then multiply that number by 4 to represent the average hours of good sun, per day, averaged over the course of the year.

    Second, all loads grow with time. Two things conspire against first time off grid folks. Try under estimate thier loads, while t the same time over estimate the solar potential. All design considerations stem from the loading.

    So for your estimated load of ~3kwh/ day, you would need a system in the 1.5 kw range, with a battery bank of perhaps 1000-1500 ah ( 12 vdc) 1500 watts of PV might produce about 80 amps ( 12 vdc) just barely in the range of that battery bank.

    I would also suggest going with a 24 or 48 vdc system, I just use 12 vdc since it is familiar.

    Welcome, and keep in touch,

    Tony
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Options
    Re: Opinions
    notes wrote: »
    Usually three day weekends and a week here and there.

    For part time use you may be able to cut back a bit on your panels... run the batteries down over the weekend and then you have 5 days with no loads to recharge them. But that's getting too far ahead... first you must pick the batteries. The battery capacity is the most important factor in deciding how much panel you need.

    75 ft between the array and the controller argues for at least a 24 volt system.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Opinions

    Nothing wrong with the 3kW hours per day estimate; that's entirely reasonable.

    But you don't need 1140 Amp hours @ 24 Volts to supply it, and that tiny array not only wouldn't recharge so much battery but wouldn't supply the desired 3kW hours either. The peak charge rate for the described system would be 2%, which would be 'maintenance' level not charging.

    A 12 Volt system would not be used no matter what: 24 Volts would be minimum. The 75' distance between array and charge controller is not difficult to deal with when using an MPPT controller because the array Voltage can be higher than system Voltage. For example the 1400-ish Watt array I described earlier could be at 48 Volts and 30 Amps. At that setting 6 AWG wire would be used over the distance. But you could also put the Voltage up higher and reduce the current and thus the wire size.

    We started out with occasional weekend visits and no electric. Both expanded to the point where we spend months at a time there when we can, and use just under 3kW hours per day. That includes refrigerator and Internet set-up (the two use almost equal amounts of power).

    As far as what vtMaps said, you could minimize the PV to a 5% peak charge and calculate for 50% DOD over two days, but that is asking for trouble as it will shorten the battery life. Perhaps that is not an issue for you, or you wouldn't mind an hour's gen time each day to do a good Bulk charge. You would not need a big generator for that either; I use a Honda 2000 which is 1600 Watts and can totally replace the 700 Watt array when necessary.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Options
    Re: Opinions
    vtMaps wrote:
    For part time use you may be able to cut back a bit on your panels
    As far as what vtMaps said, you could minimize the PV to a 5% peak charge and calculate for 50% DOD over two days, but that is asking for trouble as it will shorten the battery life.

    Asking for trouble? Depends on how much it is cycled. A lot of part timers (cabin, RV, boat) only use their system a few times per year. They do not need to take measures to prolong the cycle-life of their batteries... the batteries will die of old age before the end of their cycle life.

    But yes, I agree that 5% is on the low side for a full time cabin.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Opinions
    vtmaps wrote: »
    Asking for trouble? Depends on how much it is cycled. A lot of part timers (cabin, RV, boat) only use their system a few times per year. They do not need to take measures to prolong the cycle-life of their batteries... the batteries will die of old age before the end of their cycle life.

    But yes, I agree that 5% is on the low side for a full time cabin.

    --vtMaps

    Yes, asking for trouble. The battery may not be cycled so much but it will spend more time at a lower SOC which increases sulphation rate regardless of the number of cycles. In other words, 1,000 cycles to 75% SOC does not cause at much sulphation as 500 cycles to 50% SOC.

    But if he doesn't mind whacking it with generator power for an hour a day it won't matter. The gen in this instance would be a much cheaper way of achieving Bulk charge for the few days use, thus reducing the needed PV size and related cost. The PV would have no trouble doing the finish charging and maintaining the batteries when no one is there.

    However I suspect that once the electric is available not only will the loads increase but so will the usage time. The more pleasant the stay, the more often they'll want to be there. Been there, done that, put in $8,000 solar system. :D
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions
    However I suspect that once the electric is available not only will the loads increase but so will the usage time. The more pleasant the stay, the more often they'll want to be there. Been there, done that, put in $8,000 solar system.

    Cariboocoot, I agree 100%. When it becomes avalible from more solar they will all come to visit and stay longer. That is why I am on this site to gain as much info as possible and learn from all you gentlemen.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Options
    Re: Opinions

    Then comes the Sign " Hair Dryers and Curling Irons are Forbidden " lol. I tried a 5 amp breaker on the bathroom and I'll be darn if my girls didn't just move to another room when I wasn't paying attention. As bad as one would be, they want to use them both at the same time, 2000 Watts !!
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Options
    Re: Opinions
    Then comes the Sign " Hair Dryers and Curling Irons are Forbidden " lol. I tried a 5 amp breaker on the bathroom and I'll be darn if my girls didn't just move to another room when I wasn't paying attention. As bad as one would be, they want to use them both at the same time, 2000 Watts !!

    Get them one of these:
    http://www.amazon.com/Conair-Mini-ThermaCell-Butane-Curling/dp/B004TA7B04/ref=sr_1_2?ie=UTF8&qid=1395361673&sr=8-2&keywords=propane+curling+iron
    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
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Re: the math.quote:Otherwise you're looking at using just under 166 Amp hours @ 24 Volts. Go to 48 and you cut that down to 83. That means the 24 Volt battery bank would only need to be 664 Amp hours, not 1140.
    After reviewing older post I think I figured out a little. Correct me if I am wrong,
    4kw system/ 4000/24=166.6at 50%DOD *2 = 333.3. For 48 volt 166.6
    Now for the rest, battery bank total? Is that * 2 strings of batteries 666.6ah at 24 volts and 333.2ah at 48 volts? Formula for array size? System eff. And idle current? Also cold climate ? Trying to write this all out on paper and when time comes I have a little knowledge.
    Andy
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Options
    Re: Opinions
    notes wrote: »
    After reviewing older post I think I figured out a little. Correct me if I am wrong,
    4kw system/ 4000/24=166.6at 50%DOD *2 = 333.3. For 48 volt 166.6

    Not really clear what you are asking...

    Are you talking about a 4,000 watt (4 kWatt inverter) @ 24 volts battery bank or 4,000 Watt*Hours of energy usage per day?

    One is talking about "gallons per hour" (Watts), a rate, vs "gallons used" (Watt*Hours) or an amount.

    It is easy to get these confused... It is just like we renamed Miles per Hour "Mike's" and miles driven "Mike*Hours". Just the units historically used for electricity vs driving a car..

    400 watt load * 10 hours = 4,000 Watt*Hours used

    Notice that we have preserved the units in the math (my chemistry and physics teachers are now saying "Bill finally gets it" :roll:).
    Now for the rest, battery bank total? Is that * 2 strings of batteries 666.6ah at 24 volts and 333.2ah at 48 volts? Formula for array size? System eff. And idle current? Also cold climate ? Trying to write this all out on paper and when time comes I have a little knowledge.
    Andy

    Once I understand your needs, we can go through the rest of your math/questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Bill, I am talking about 4000wh from early post by Ccriboocoot. Just trying to understand how he came up with battery and array size. My needs are 2891 max wh per day / average wh per day 1221. Just trying to write it all out to help me better understand.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Options
    Re: Opinions

    OK, here we go with "nominal" (read conservative) design for solar power at a full off grid home/cabin used 9+ months of the year. I will list the range of sizing Rules of Thumbs--Typically if this is a weekend/seasonal cabin, you could size stuff towards the smaller end of the range. Note that none of the sizing at this point "cares" about specific hardware/battery type/voltage/etc... Just some basic math. Once the system is "sized", then you start picking the hardware that fits the sized system.

    First, the battery bank. Very simply, the average lead acid battery bank should store ~1-3 days of power and 50% maximum discharge for long(er) battery life. Assuming you want an average of 4,000 WH of 120/240 VAC power per day:
    • 4,000 WH of AC power per day * 1/0.85 typical Inverter Eff * 1/48 volt battery bank * 2 days of storage * 1/0.50 max discharge = 392 AH @ 48 volt battery bank
    Picked 48 volt battery bank because, typically, >600-900 AH battery banks (~2*392AH=784AH @ 24 volt) because "expensive" and difficult to wire at the higher currents need to run on a lower voltage battery bank. 2 days of storage (25% discharge per "night" is a good size bank without spending a lot of money on over-sizing--Use a Genset for when bad weather/loads exceed short term solar charging abilities).

    Next, we need to charge the battery bank... Two calcualtions--First is sizing to get enough "charging current" to the battery bank. Typically that is ~5% to 13% of the battery bank's 20 Hour Rated capacity (392 AH * 10% = 39.2 Amps "nominal" charging current):
    • 392 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,502 Watt array minimum
    • 392 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 3,004 Watt array nominal
    • 392 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 3,905 Watt array "cost effective" maximum
    Normally a 10% rate of charge works well for a typical off grid home. If you have significant loads during the day (irrigation, home office, etc.), you may need to take those "day time" loads into account (i.e., if you have irrigation and well pump running 6 hours per day, then you want the solar array to support both the pump running and battery charging at the same time). Going above 13% rate of charge is OK (upwards of 20-25%), but is expensive and you should use a solar charge controller with a remote battery temperature sensor to make sure you don't get thermal runaway (battery gets hot, charging voltage drops, controller thing battery needs more charging current, battery gets hotter, repeat to meltdown/fire).

    Note that an "oversized" battery bank does "cost you". Besides the expense of buying the first bank and replacing every 5-8 years or so, you have to have a larger solar array+charge controller to make sure the battery bank has enough charging current (even if you do not deeply cycle every day).

    Next, we need to size the charging based on the amount of sun you get and when you want to use power. Normally, I look at the 12 month average sun, and toss the bottom three months (poor weather, use a generator/conserve power during bad weather).

    Using PV Watts for upper Michigan (Houghton), fixed array tilted to latitude of 45 degrees, facing south:
    Month    Solar Radiation (kWh/m 2/day)
    1      2.56     
    2      3.70     
    3      4.68     
    4      5.72     
    5      5.25     
    6      5.56     
    7      5.58     
    8      5.38     
    9      4.48     
    10      3.20     
    11      2.09     
    12      2.11     
    Year      4.19
    

    Toss the bottom three months and use 3.20 hours of sun for the "break even" month (might need generator use during bad weather). For much of the US, we use 4 hours minimum sun, but in your case you have very poor solar in winter. Your choice of more array or more generator run-time:
    • 4,000 WH per day * 1/0.52 system eff * 1/3.2 hours of sun = 2,404 Watt "break even October" array
    So, that is the basic sizing of an off grid system for full time home. A solar array (I would recommend) would range from 2,404 Watts to 3,905 Watts, with 3,004 watt array being the "minimum" that would support my guess at your needs.

    If this was an RV, your battery bank may be 1 day of storage and your solar array is whatever you can fit/afford on the unit.

    In the "olden days" when solar panels were expensive ($10+ per watt) and batteries were cheap--There was a recommendation to "over-size" the battery bank. That was bad advise back then (unless you wanted to run your genset "a lot"), and with solar panels in the $1-$2 per Watt range, it is usually better to "over panel" an off grid installation. Battery bank is happier and you spend less money on very expensive fuel.

    You can put the above into a spread sheet very easily--I don't because I want folks to understand the formulas and assumptions that have been made. If it is in a spread sheet, it all becomes "magic" and nobody understands what tradeoffs were made.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Thanks Bill, I need to write it all out to understand. Just have to sneak away from wife to list it all out. She thinks I am back in school.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Bill, thanks again, getting it all to pen and paper. Question, Houghton Mi. is 4-5 hours north/west of our site. Greenbay is 1.5 hours south/west. Using PV Watts link you attached I notice a increase in average minutes. Would this change any thing for the better?
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Options
    Re: Opinions

    Going for Green Bay:

    Month    Solar Radiation (kWh/m 2/day)
    1      3.31     
    2      4.17     
    3      4.94     
    4      5.21     
    5      5.53     
    6      5.52     
    7      5.83     
    8      5.05     
    9      4.53     
    10      4.08     
    11      2.59     
    12      2.59     
    Year      4.45
    

    You get a bit more winter production (20%?). It is "more", but with solar/off grid power, it is not a huge difference. More or less, given weather/measurement errors/etc... Anything within +/-10% of what is predicted with PV Watts and the formulas--It pretty dead on "correct".

    In engineering, a factor of 2 is a "noticeable" change, and a factor of 10 difference is a "day/night" change (you can pretty much ignore the smaller effect).

    You can look at using a 2 axis tracking array (PV Watts with tracking):
    Month    Solar Radiation (kWh/m 2/day)
    1      3.99     
    2      5.13     
    3      6.06     
    4      6.95     
    5      7.96     
    6      8.27     
    7      8.60     
    8      6.79     
    9      5.86     
    10      4.91     
    11      3.02     
    12      3.10     
    Year      5.89
    

    You can see a 50% increase in winter production and some pretty good increase in summer production too...

    But trackers are expensive (and need maintenance). Just increasing the number of solar panels by 50% may cost less and give you similar amounts of power.

    You can even look at "virtual" trackers... Increase your array size by 50%, and have 1/2 of the panels facing south east, and the other 1/2 facing south west.

    Trackers (and virtual trackers) can increase the hours per day of solar current to charge the battery bank. In general, short days like you see up north, are really hard on batteries (lots of current for only a few hours per day can shorten battery life).

    The problem is there is no "right answer" you can play with PV Watts (do two calculations, 1/2 array SE other SW, and add the results together) and compare that with the cost of a 2 axis tracker. See which works better for you (vary the SE/SW headings and see how it affects the total harvest).

    Many folks up north do something a bit different. They make racks that they can tilt. Lay back -15 degrees for summer, and mount near vertical to shed snow in winter (and can get good reflections from snow fields too). Mount array high enough to allow room for snow to shed.

    If you roof mount, there can be issues with snow/ice--I will let others here with first hand experience talk about that.

    If the cabin is not occupied in winter, just a couple panels on a vertical wall can be enough to keep the battery bank charged (cold batteries have less self discharge/longer storage life).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Bill, thanks for all your help so far. I think I picked batteries, 48 volts, 8 US RE L16XC @401AH. That's as close as I can find on my budget from you suggesting 392ah. Solar array would have to increase to a minimum of 1536 to a maximum of 3994 if my math is correct. I am having trouble with inverter. I called AWS and they suggested 2 Outbacks stacked, called it FP2 system. Said with my total watts and surge I would need minimum 4500 watt inverter. Is this a good idea? I am looking at magnum MS4548PAE also. Any thoughts?
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • BB.
    BB. Super Moderators, Administrators Posts: 33,442 admin
    Options
    Re: Opinions

    I will leave it to others regarding selection of the inverter...

    My concern is you are building quite a large systems (4kWH per day)... Given that you are not even running a refrigerator or living there full time at the moment, I would be guessing that this is 2x to even 4x larger system than you can really make cost effective use of.

    What is your opinion of running a Honda eu2000i (1,600 watt) genset during the day (when you need to power heavier loads like a small skill saw, run the toaster, etc.)?

    Batteries age if they are used or not... That is a good size battery bank and would probably last 5-8 years (just a wild guess) if there are no "mistakes" (i.e., battery homicide).

    If you could live with a 1-2 kWH per day system with a nice quite little genset like the Honda (and 1-2 gallons of fuel per day)--Would that work well for the next few years for you?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Opinions
    notes wrote: »
    Bill, thanks for all your help so far. I think I picked batteries, 48 volts, 8 US RE L16XC @401AH. That's as close as I can find on my budget from you suggesting 392ah. Solar array would have to increase to a minimum of 1536 to a maximum of 3994 if my math is correct. I am having trouble with inverter. I called AWS and they suggested 2 Outbacks stacked, called it FP2 system. Said with my total watts and surge I would need minimum 4500 watt inverter. Is this a good idea? I am looking at magnum MS4548PAE also. Any thoughts?

    What on Earth? :confused:
    Two 3.5 kW Outbacks for 120 VAC is 7kW capacity. That is a huge amount of power.
    I don't recall seeing anything in this thread (and I just reviewed it) about your maximum simultaneous loads. That is what you size an inverter from: it has nothing to do with kW hours used.

    Even with the microwave, water pump, and septic pump my VFX3524 doesn't come close to full power output - because it's not all on at the same time. That is what you've got to look at when sizing an inverter. How NAWS came up with such a whopping big demand I don't know. What did you tell them you needed?
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    Options
    Re: Opinions
    BB. wrote: »
    I will leave it to others regarding selection of the inverter...

    My concern is you are building quite a large systems (4kWH per day)... Given that you are not even running a refrigerator or living there full time at the moment, I would be guessing that this is 2x to even 4x larger system than you can really make cost effective use of.

    What is your opinion of running a Honda eu2000i (1,600 watt) genset during the day (when you need to power heavier loads like a small skill saw, run the toaster, etc.)?

    Batteries age if they are used or not... That is a good size battery bank and would probably last 5-8 years (just a wild guess) if there are no "mistakes" (i.e., battery homicide).

    If you could live with a 1-2 kWH per day system with a nice quite little genset like the Honda (and 1-2 gallons of fuel per day)--Would that work well for the next few years for you?

    -Bill

    Excellent advice, really maybe just start small and see if this is for you.

    Bill, one of the things I am doing alot now with virtual tracking is not only adjusting the elevation but being able to adjust the azimuth for winter. Up here at latitude 37.5 we can do a east, south east array and a west south west array in summer for the long days. The mean season of winter can move the arrays to point more south at the south east and south west. On a mountain with wind over 100mph you get a litlle more strength in the mounts than a Wattsun tracker. Excellent article this month in solar pro on tracking BTW. I think the maintenance part that gets talked about here is often overstated with good equipment. My family of Wattsun trackers about the world is an excellent performer and a learning experience to just watch.

    And, thanks for the rain! We finally filled up. Usually full by the winter solstice.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Cariboocoot, I sent them same info as my post, #8 on there load analysis spread sheet. Bill, I don't mind going that route. I would like to keep generator fuel as propane, so no problem. I am looking at smaller generators, Beem inverter generator for one and also Honda with conversion to propane. The Beem is propane fuel from factory. As for loads, I already removed toaster and got a small energy star microwave. Current one was way to big. Bill, we are running a separate gas generator for all shop tools, vacuum and outdoor power as needed.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Opinions
    notes wrote: »
    Cariboocoot, I sent them same info as my post, #8 on there load analysis spread sheet. Bill, I don't mind going that route. I would like to keep generator fuel as propane, so no problem. I am looking at smaller generators, Beem inverter generator for one and also Honda with conversion to propane. The Beem is propane fuel from factory. As for loads, I already removed toaster and got a small energy star microwave. Current one was way to big. Bill, we are running a separate gas generator for all shop tools, vacuum and outdoor power as needed.

    Post #8 contains information about Watt hours. This is irrelevant to sizing an inverter.
    Example: 100 Watt loading running 24 hours uses 2400 Watt hours but does not require a 2.4kW inverter to run it.

    That's why you have to know what all will be on at the same time.
    If I turn on the well pump (800 Watts) septic pump (1200 Watts) and microwave (1000 Watts) all at the same time that's 3000 Watts, and I've still got 500 Watts capacity to run the 'frige and everything else. Certainly no need for 7kW of inverter.
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Cariboocoot, I have it all written down at home, I will post later this evening.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan
  • notes
    notes Solar Expert Posts: 52 ✭✭
    Options
    Re: Opinions

    Cariboocoot, I don't know how he arrived at that figure.My total wattage is 3710, possible 2450 at one time. This is what was returned from sales staff, 1331.1Wh average, 650W solar, 3116Wh Max, 12V, 680Ah batteries, 4841W max*** With 2 FX2524T inverters. I also wanted 48 volt system, but that was ignored.
    4-Canadian Solar CS330 in series/TraceSW4024/Midnite Classic 250 with Whiz Bang jr/8 L16-370ah 4S2P/ Propane Honda EU2000/Propane Champion3800/electric refrig/Wood heat/Propane tankless water heater/ Grundfos SQE well pump. adding 6 REC Twin Peak 350 watt panels
    Off grid in Upper peninsula Michigan