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Thread: Southern Alaska winter time sun hours for a off grid solar and wind system

  1. #1

    Default Southern Alaska winter time sun hours for a off grid solar and wind system

    I was offered a job there in Juneau area and i was looking to retire there in the future ..It going to be about 45 miles south of Juneau on a small 1/2 half sized lot .. The land has great view of the sun in the southern sky as it pass overhead along with the area is also great for a small wind turbine for there is a breeze comeing off the ocean dureing the day and it strong enough to run a small turbine system as the day i wa there the wind was going like crazy at a good clip ..The place is going to be a weekend getway starting out at first then after retirement it going to be a full time place there

    I have done the home work for the Amp hours that i'm going to use in the cabin with all the appliance's i have chose for the place ..Everything i chose for the place is 12.volt or enegry star rated type appliances to squeeze out the lowest wattage i can out of the 120.volt items i have bought for use at the place ..

    My biggest problem is trying to figure out the winter months from Oct To Feb time frame and how many actul hours of sun i will get dureing the days along with the small wind turbine system for i need to make the solar panel to get the max amount of sun light to make power for the place..

    My system design calls for the panels -x-six Kyocea KD135GX 12.volt panel's on a pole system with a Air X 200.watt air tubine on a 15.ft tall pole system to recharge the battery bank and wire as they are need for use to charge the bank unit as it need

    As part of the planed system is to use a Outback VFX3648 Flexpowe all in one system for the inverter along with dc and ac fuse boxs and multi other units put into one unit for makeing it easy to wire up and mount on the mud room wall where the battie rack is going to be at

    The batties are Sun Xtended 12,volt PVX 2580L AGM sealed Batties -each batties has a 255 amp hours over a 20 hour time frame ..

    The system i have design for the cabin is design to use a two battery bank set up of 10-.battery's each with the system working as follows

    1-bank 1-is online running the cabin and provideing all the power as it need to all the units that are on and running at the time from the tv to laptop computer to the rv water pump for the sinks and shower ..

    2-bank-2-is off line and beening charged with the solar and wind combo system and the reason why for a week long charge time i was told this alot better for the battery bank to allow it to be charged up over time than to try and force the charge on the bank like a gen set does when it chargeing the system ..


    The bank's are design to last seven day with a five day back up in the bank system for a total of 12 days if the sun is not shineing and the other bank is not ready to go right on the seven day mark for switch over to the freshly charged bank ..

    The heavyest loads on the system are done on diff days to allow the bank not to over taxed the battery bank it self and make them last for a long time intill ..

    The laundry is handle on a Sat morning and all the bakeing for the week is done on a Wed dureing the week and the rest of the week is the basic everyday items like dvd player and tv or laptop computer with sat internet set up for use ..The lights are all led low power type and the water pump for the washer unit and shower system is rv high pressure 12.volt unit to handle those chores for pumping of the water from the water stowage tank into the sinks and shower and washer unit

    So what do you think of the off grid system i have design for a small off grid cabin there for future use there in Alaska

  2. #2

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    Welcome to the forum.

    You're going to want to run the PV WATTS program for your locale. http://www.nrel.gov/rredc/pvwatts/
    It will tell you what you can expect for solar harvest in your area. Speaking as a fellow "North of 50" resident, I can tell you it's not good. Along about December we run out of sun. Your proposed 810 Watts of panel will disappoint. On a 48 Volt system with 255 Amp hours you're going to want at least double that in panel. I have 700 Watts on a 24 Volt system with about the same battery capacity and it is inadequate without careful load shifting. It is not used in Winter. And a back-up generator power is a must.

    As for your indications of having multiple battery banks and many days' reserve ... forget it. As mentioned above those panels are barely adequate for recharging one bank of 255 @ 57 Volts. A generator is a far cheaper alternative to massive battery banks and huge arrays. If you can set up your system with one bank that gets discharged only 25% for one day, then you have 2 days capacity right there (maximum discharge of 50%). On the third day, start the generator.

    Not sure why you picked AGM's either. Expensive on a per Amp hour basis, and possibly not the best investment for a first battery set. It's very easy to under/over charge batteries and AGM's aren't forgiving of that (as opposed to FLA's). Better to start with some cheap golf cart type batteries, then change for the others after you've got everything "dialed in". Nothing like being able to take an SG reading to know what the bank is doing. Battery monitors are good too, and a must for AGM's.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #3

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    I have been looking at the numbers the one company give me and i been trying to figure them out by there system and i can get the small figures with my math it seams ..

    The biggest with a fuel driven system it the transporting of the fuel to the location it done by a atv type vehicle or a person back and it still a major chore to get the fuel back to the place where the clearing is for cabin and the solar and wind set up for the place

    The place is located about 20 min walk from the one major road in the area and it not bad with a atv or a 4 wheel drive truck but dureing the fall or when it raining it a little hard to get back into the place

  4. #4
    Join Date
    Jun 2003
    Location
    pittsburgh, pa
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    10,278

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    funny thing about the sun is that when you want and need it the most is when it's there the least, aka winter. wind may help, but not with an air x. wind turbines are more mechanical and subject to wear and breakdown and you know when that will happen. see the thread on swwp created by truth squad.

    it isn't totally bleak though as when the sun shines on pvs with snow on the ground it gets a bit of a boost because of reflection. also, there is talk of some turbines doing ok and are using the new classic controller with very good success. keyturbocars is very into this aspect and it is still ongoing in tweaking it. he has shown nearly 4kw on a 2kw turbine.

    if you are worried of gassing of fla types indoors as your reason for going agm i can then understand starting off with the agms. do be careful that they aren't overcharged as they are a more expensive battery, but they are also more efficient than fla types too. i totally agree with the generator and just have one large battery bank that is good for a few days, but the final decision will be yours on the battery bank for a genny sized right can supplement the loads to your place while also giving a charge to the batteries if you have the extended gloom of winter over your head. keep reading up on things so you may know if you'd want to make any changes in your plans before you start into it.
    NIEL

  5. #5

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    One of the main reason i chose the AGM was the fact that i was going to be doing a long slow charge to allow the battery bank to be charged over a longer time frame and not worry about the units heating up dureing the chargeing time frame with each day it recharge a little intill the battery bank is bought back to full charge ..

    The battery banks is in a off set room like a mud room set up where it been vented and fans system to alllow anything that does happen to escape from the area and not become a problem

    the total daily watt's without the cooking and laundry loads on the unit is less than 300.watts a day with everything beening used that day ..

    The Air X Marine design was the idea unit in my thinking because of the design for use on sailboats in the open ocean air and the land is located about 4 miles for the ocean and have the problems with the salt and other elaments that are in air and areas because of the ocean system that is around the areas ..I figure it would be beter to go with a smaller set up like a Air X marine unit that i can take down and do basic PMS on it to keep it running and putting it up and down

  6. #6
    Join Date
    Jun 2007
    Location
    Williams Lake, BC
    Posts
    3,088

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    Henry, did I read your post correctly about the number of batteries you will have, 10 x 12 volt batteries in each string...

    If this is correct you will have them wired up in a 120V DC configuration and you are planning on using 48 volt equipment?

    You mention that you will have 2 strings, that makes 20 batteries that could make 5 strings at 48 volts, this is not an easy task to get all the banks evenly balanced.

    please confirm the battery bank setup you plan on using.

    Eric
    100% Off Grid @ 51* 46' N lat 124* 44' W long

    New House system: coming - 2 arrays @ 2240W
    CL150&Epanel 2 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah
    + CL150 2@120W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
    Cotek ST1500W inverter, TBS 30a-24v Omni-charger, Honda Eu3000is,

    Guest cabin system: 3 - 70W panels to SB 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

  7. #7
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    21,262

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    There can be some very difficult issues with large battery banks and "slow charging"...

    Basically, the problem is that Lead Acid Batteries have a few operating points which they do not like:

    • Cycling below 20% state of charge--Can permanently damage one or more cells/batteries. (weak cell gets "reverse charged" by neighbors and is pretty much killed--a more difficult problem "to see" on 48 volt battery banks where 2-4 volt bank voltage drop does not shutdown equipment as it would on a 12 volt bank).
    • Keeping a Battery Bank below 75% state of charge for days/weeks. The lead sulfate begins to crystallize and removes the compound from any more chemical relivance in the battery's storage of energy (i.e., quickly reduces Amp*Hour capacity. Most systems would need new batteries when ~20-50% of capacity is lost (due to sulphation and other causes).
    • Another "softer" rule of them is try not to cycle below 50% state of charge... The more often you do that, the shorter the cycle life of the battery... The reason is it is a "soft rule of thumb", from my point of view, is that if you buy 2x the amount of batteries for to avoid the 50% discharge, the bank will only last ~2.2x as long--So $$$/Usefulness becomes more of a wash (bank lasts 2x longer buy you have to by 2x the number of batteries).

    So, we tend to recommend that people do not go below 5% rate of charge with their solar array (i.e., 100 AH batter should have a minimum of 5% charging current from array or AC battery charger)...

    Yes, there are good reasons to not follow the above rules (at times), but try to stay within the rules.

    Another driver for costs is fuel usage. Try to have your genset operating at a minimum of 50% of rated load... That will give you a reasonable kWH/Gallon of fuel (just like MPG).

    For example, a small bank with a small genset (say a Honda eu1000 or eu2000 family) driving a smaller AC charger will use probably just as much fuel as a 4x larger battery bank, with 4x larger genset, and 4x larger AC battery charger.

    And if the loads are not kept high on larger genset (sneak down to 20% or less), you may use 2-3x as much fuel trying to keep everything charged during the winter (as well as much more upfront costs for batteries, genset, charger, etc.).

    Fuel choice will affect storage, generator costs, etc... Diesel, propane, gasoline. Diesels tend to be larger (5kW and up) and really need the 50-60% minimum loads for proper operation (but are more fuel efficient on a kWH/gallons basis)...

    5kW diesel, 2.5 kW minimum load. Honda eu2000i, 400 watt minimum relatiely fuel efficient load (and darn quiet too).

    Getting a small 1,600 watt generator plus a cheap 3.5-5kW for the occasional bigger loads (and emergency backup) works well too.

    And there are some very nice Propane Conversions for the smaller gasoline gensets (propane is the least energy per gallon of fuel, and obviously hauling pressure tanks around.

    Start playing with some real numbers (Watt*Hours per day Summer vs WH per day Winter, etc.). and size out the "large" and small system and comparing their costs and usefulness for you.

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  8. #8

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    Quote Originally Posted by westbranch View Post
    Henry, did I read your post correctly about the number of batteries you will have, 10 x 12 volt batteries in each string...

    If this is correct you will have them wired up in a 120V DC configuration and you are planning on using 48 volt equipment?

    You mention that you will have 2 strings, that makes 20 batteries that could make 5 strings at 48 volts, this is not an easy task to get all the banks evenly balanced.

    please confirm the battery bank setup you plan on using.

    Eric
    The string is design with each bank beening 10 batties in the string wired for 12.volt use not 48 volts or 120.volt and it was design from the get go as a 12,volt system

    The design to have one bank on line and one bank off line beening charged at the time in a week long chargeing of the battery bank and that way the system is not alot of stress on the system in the long run .

    The 120 volt power needs runs through a inverter to meet that need

  9. #9

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    I just finish reading the whole thread of Air X breeze wind turbine as a part of the add on to the system .. The scareing part of some of the post is that some of the comments about the service and the product going down hill fast and it not going to get better so i been looking at diff places for another turbine

  10. #10
    Join Date
    Jun 2007
    Location
    Williams Lake, BC
    Posts
    3,088

    Default Re: Southern Alaska winter time sun hours for a off grid solar and wind system

    Henry the VFX 3648 model inverter uses 48 volt DC in, 3600 VA 120V AC out, that is why I said you have to wire the batteries differently.

    See here:

    http://www.outbackpower.com/products...rter/off_grid/

    If you want to go 12v you will need a different inverter possibly an FX2012 model, also shown in the above link

    hope this helps

    Eric
    100% Off Grid @ 51* 46' N lat 124* 44' W long

    New House system: coming - 2 arrays @ 2240W
    CL150&Epanel 2 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah
    + CL150 2@120W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
    Cotek ST1500W inverter, TBS 30a-24v Omni-charger, Honda Eu3000is,

    Guest cabin system: 3 - 70W panels to SB 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

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