Off Grid design help

Hello,

I am trying to design a system for our off grid yurt. I am hoping to run my computer for 4-5 hrs a day, a Danby 7.1 cu ft. converted chest fridge, and a few lights. I am estimating that I need about 150wh/day for the computer, 250wh/day for the fridge, and 100wh/day for misc. So it seems I need 500wh/day not factoring in efficiency losses.

I believe I've seen 85% efficiency for inverters. If so, I will need 588 wh/day of battery storage. So for a 12v system, this would be 49 aH/day. With a 50% discharge and 3 day reserve, I would need about 284 ah battery bank.

I plan on using 6v batteries. Which are 207ish aH each. Thus I will either need 4 batteries or just go with 2 and run the generator a bit more.

I found the following information regarding sun hrs for my area. http://rredc.nrel.gov/solar/pubs/redbook/PDFs/OR.PDF. It seems like Nov-Feb I am definitely going to need use a generator. However, the fridge won't be as necessary as the temps are cool enough outside to use an ice chest if needed.

We have access to grid power about 1/2 mi away at my in-laws where we will keep a freezer and can use larger shop tools when needed.

I'm hoping to get a little help figuring out what I would need for my system. Should I run 12v or 24v? Is it better to run to generator a bit more or the get more batteries and panels? How do I determine what size array I need? What about the inverter size (800w?)? How about sizing the generator?

Also, there is a Honda ev4000 RV generator on craigslist for $400 with approx 900 hrs on it. My feeling is that this will be a bit oversized for what I need. Do you think I will be better off getting a honda eu1000/2000 generator? Or is the fuel consumption not that different. It would be nice to run a small a/c for 10 - 20 days in the summer, but that isn't necessary.

Thanks in advance for any help.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Welcome to the forum Rodney.
    rodney757 wrote: »
    I am trying to design a system for our off grid yurt. I am hoping to run my computer for 4-5 hrs a day, a Danby 7.1 cu ft. converted chest fridge, and a few lights. I am estimating that I need about 150wh/day for the computer, 250wh/day for the fridge, and 100wh/day for misc. So it seems I need 500wh/day not factoring in efficiency losses.

    Good start on the numbers... Have you used a Kill-a-Watt type energy meter to measure your loads for several days (to get average WH/kWH per day) yet?

    Your 500 Watt*Hour per day load sounds a a bit small to me if you are including any sort of refrigerator--I would be guessing closer towards 800 WH per day just for the fridge. Even the small "bar fridge" types can use almost as much energy as a simple full size refrigerator (~290 kWH per year for bar fridge, and ~340+ kWH per year for full size fridge/freezer). Some folks have converted a chest freezer into a chest refrigerator and can get down towards 250 WH per day (many spouses do not like food access for a chest refrigerator).

    Also, a "standard refrigeration compressor" (typically about the same size motor is used in a small fridge as a full size fridge) takes a lot of power to start... Roughly a 1,200 to 1,500 watt AC inverter is a good start point. And you need a large enough battery bank to supply the starting current too (1,200 Watt inverter would suggest around a 480 AH @ 12 volt battery bank minimum. Which would support around.
    • 480 AH * 12 volts * 0.85 inverter eff * 1/2 days of storage * 0.50 maximum discharge (for longer battery life) = 1,224 Watt*Hour per day average system load (given my assumptions)
    Also, remember if you run a 1,200 Watt AC inverter 24 hours per day draws upwards 20 Watts--Or 20 Watts * 24 hours per day = 480 WH per day. That almost doubles your 500 Watt estimated loads.

    I believe I've seen 85% efficiency for inverters. If so, I will need 588 wh/day of battery storage. So for a 12v system, this would be 49 aH/day. With a 50% discharge and 3 day reserve, I would need about 284 ah battery bank.

    Personally, I would design your system for a minimum battery bank of:
    • 2 parallel strings of golf cart batteries at 12 volts = 4 batteries
    • 2x 207 AH = 414 AH @ 12 volt battery bank
    • Or look at different batteries or a 3rd parallel string (2-3 maximum parallel strings is my suggestion--Although If you can keep it to 1 or 2 strings--much better in my opinion)
    • 3x 207 AH = 614 AH battery bank
    I plan on using 6v batteries. Which are 207ish aH each. Thus I will either need 4 batteries or just go with 2 and run the generator a bit more.

    Need to know more about the refrigerator starting surge--They just "kill" off grid power system designs. You add a typical AC fridge, and your small/cheap system just when "midsize" and no longer cheap.

    If your cooling loads are seasonal--You might think about a getting a used RV propane type refrigerator (there are 12/24 VDC refrigerators, but they are also very pricey in their own right). Be careful, because there are AC/DC/Propane refrigerators--And the AC function is very inefficient (the AC simply replaces the propane flame for heat).

    Your battery bank is the "heart" of your system. You need to understand your loads so you can choose the right battery bank to support those loads. In general, when a battery bank approaches 800 AH in capacity--At that point, you should think about going to 24 volt (or 48 volt) battery bus.
    I found the following information regarding sun hrs for my area. http://rredc.nrel.gov/solar/pubs/redbook/PDFs/OR.PDF. It seems like Nov-Feb I am definitely going to need use a generator. However, the fridge won't be as necessary as the temps are cool enough outside to use an ice chest if needed.

    We have access to grid power about 1/2 mi away at my in-laws where we will keep a freezer and can use larger shop tools when needed.

    I'm hoping to get a little help figuring out what I would need for my system. Should I run 12v or 24v? Is it better to run to generator a bit more or the get more batteries and panels? How do I determine what size array I need? What about the inverter size (800w?)? How about sizing the generator?

    Before I go further into the math--What do you think about my load discussion? Are you really constrained by price? Would a propane refrigerator be OK for your needs. Is this a long term situation--3-5+ years worth of living? Remember if you make ice+add warm food to the refrigerator daily--Its WH per day loading goes up by quite a bit (if you are using the fridge 9 months or more a year, then a full electric+solar fridge is probably the better choice).
    Also, there is a Honda ev4000 RV generator on craigslist for $400 with approx 900 hrs on it. My feeling is that this will be a bit oversized for what I need. Do you think I will be better off getting a Honda eu1000/2000 generator? Or is the fuel consumption not that different. It would be nice to run a small a/c for 10 - 20 days in the summer, but that isn't necessary.

    Let us wait until we understand your power needs more... Basically, a gasoline genset is reasonably fuel efficient >~50% of rated load. And not very fuel efficient below ~25% of rated load. It does not sound like you would use 2,000 Watts of power very often out there. And noise--RV unit should be pretty quiet--As are the eu2000i/1000i units.

    Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    I've heard the 250 wh numbers for small chest freezer conversions, but in the real world I would want to be sure to have enough.

    On types of inverters, I would suggest looking for a pure sine wave inverter, Likely things will run fine of a modified sine wave, but they won't run as efficiently (things with motors, like compressors will use more electric) and you will shorten their lives. Compare inverter chargers against independent inverter and chargers. Though with your minimal needs, perhaps independent units would be the way to go.

    With long months of minimal sun, I'd look to stay in the top 20% of the battery bank through your 8 months of somewhat sunny weather, and have the extra reserve for those cloudy months. If I were designing a system, I'd like a somewhat over paneled system for those cloudy days.

    With the long period of cloudy weather, I'd want a generator, but I'd think the large Honda would be to big to run effectively.
    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.
  • rodney757
    rodney757 Registered Users Posts: 4
    BB. wrote: »
    Welcome to the forum Rodney.



    Good start on the numbers... Have you used a Kill-a-Watt type energy meter to measure your loads for several days (to get average WH/kWH per day) yet?

    I just rented one from the library yesterday. The only thing I measured was my computer with was drawing about 28w on average. However we are currently camping w/o power while we are building the yurt. I don't really have a way of measuring our power usage as everything is packed away.
    Your 500 Watt*Hour per day load sounds a a bit small to me if you are including any sort of refrigerator--I would be guessing closer towards 800 WH per day just for the fridge. Even the small "bar fridge" types can use almost as much energy as a simple full size refrigerator (~290 kWH per year for bar fridge, and ~340+ kWH per year for full size fridge/freezer). Some folks have converted a chest freezer into a chest refrigerator and can get down towards 250 WH per day (many spouses do not like food access for a chest refrigerator).

    We are planning on using a converted chest refrigerator. So I was hoping we would be down in the 250 wH range.
    Also, a "standard refrigeration compressor" (typically about the same size motor is used in a small fridge as a full size fridge) takes a lot of power to start... Roughly a 1,200 to 1,500 watt AC inverter is a good start point. And you need a large enough battery bank to supply the starting current too (1,200 Watt inverter would suggest around a 480 AH @ 12 volt battery bank minimum. Which would support around.

    I've read about people using capacitors to run a fridge off of a 300w inverter. I was hoping that I would be able to modify the chest freezer to get by with an 800w inverter. The Danby chest freezer I'm looking at draws 1.2a @ 115v.
    • 480 AH * 12 volts * 0.85 inverter eff * 1/2 days of storage * 0.50 maximum discharge (for longer battery life) = 1,224 Watt*Hour per day average system load (given my assumptions)
    Also, remember if you run a 1,200 Watt AC inverter 24 hours per day draws upwards 20 Watts--Or 20 Watts * 24 hours per day = 480 WH per day. That almost doubles your 500 Watt estimated loads.

    Maybe the best thing would be to have a dedicated inverter for the fridge that was turned on by a relay when the thermostat tripped. I'm not sure if there are battery powered thermostats or if I would need a small inverter for the thermostat to run as well.

    I would think that a small 300w inverter that we only turned on when needed would be plenty when I wanted to use my computer/lights.
    I believe I've seen 85% efficiency for inverters. If so, I will need 588 wh/day of battery storage. So for a 12v system, this would be 49 aH/day. With a 50% discharge and 3 day reserve, I would need about 284 ah battery bank.

    Personally, I would design your system for a minimum battery bank of:
    • 2 parallel strings of golf cart batteries at 12 volts = 4 batteries
    • 2x 207 AH = 414 AH @ 12 volt battery bank
    • Or look at different batteries or a 3rd parallel string (2-3 maximum parallel strings is my suggestion--Although If you can keep it to 1 or 2 strings--much better in my opinion)
    • 3x 207 AH = 614 AH battery bank


    Need to know more about the refrigerator starting surge--They just "kill" off grid power system designs. You add a typical AC fridge, and your small/cheap system just when "midsize" and no longer cheap.

    If your cooling loads are seasonal--You might think about a getting a used RV propane type refrigerator (there are 12/24 VDC refrigerators, but they are also very pricey in their own right). Be careful, because there are AC/DC/Propane refrigerators--And the AC function is very inefficient (the AC simply replaces the propane flame for heat).

    Your battery bank is the "heart" of your system. You need to understand your loads so you can choose the right battery bank to support those loads. In general, when a battery bank approaches 800 AH in capacity--At that point, you should think about going to 24 volt (or 48 volt) battery bus.

    I've thought about a propane fridge, but it seems that it might not be the best choice in the long run. The upfront cost as well as the need to continually rotate propane tanks doesn't sound appealing. Does anyone know if the DC fridges, such as the sundazer, are that much more efficient? Or is the only efficiency to be gained is the inverter loss?
    Before I go further into the math--What do you think about my load discussion? Are you really constrained by price? Would a propane refrigerator be OK for your needs. Is this a long term situation--3-5+ years worth of living? Remember if you make ice+add warm food to the refrigerator daily--Its WH per day loading goes up by quite a bit (if you are using the fridge 9 months or more a year, then a full electric+solar fridge is probably the better choice).



    Let us wait until we understand your power needs more... Basically, a gasoline genset is reasonably fuel efficient >~50% of rated load. And not very fuel efficient below ~25% of rated load. It does not sound like you would use 2,000 Watts of power very often out there. And noise--RV unit should be pretty quiet--As are the eu2000i/1000i units.

    Your thoughts?

    -Bill

    So this is a medium to long term situation. Right now we are looking at 3-5 yrs. After that, we're not sure if we will stay or build a place closer to the in-laws where there is power available. I am not overly constrained by price, but I would rather by less power with quality components then more power and cheaper components. That said, I don't necessarily need name brand equipment as long as it is fairly reliably and will meet our needs. I believe that we are more then comfortable living with a very minimal power system. We have seriously thought about living with no power, however I do think the ability to work from home and to have a fridge would be nice.

    Thanks so much for the detailed response. I look forward to hearing your thoughts.
  • rodney757
    rodney757 Registered Users Posts: 4
    Photowhit wrote: »
    I've heard the 250 wh numbers for small chest freezer conversions, but in the real world I would want to be sure to have enough.

    On types of inverters, I would suggest looking for a pure sine wave inverter, Likely things will run fine of a modified sine wave, but they won't run as efficiently (things with motors, like compressors will use more electric) and you will shorten their lives. Compare inverter chargers against independent inverter and chargers. Though with your minimal needs, perhaps independent units would be the way to go.

    With long months of minimal sun, I'd look to stay in the top 20% of the battery bank through your 8 months of somewhat sunny weather, and have the extra reserve for those cloudy months. If I were designing a system, I'd like a somewhat over paneled system for those cloudy days.

    With the long period of cloudy weather, I'd want a generator, but I'd think the large Honda would be to big to run effectively.


    It makes since to have an over paneled system. However is the cost/benefit worth it? Or would I just be better off running the generator every couple days for the 4 months? Maybe the way to go is to design the system to be able to add panels next year if needed. I think that you can't really add batteries though. Correct?
  • lancashire_hotpot
    lancashire_hotpot Registered Users Posts: 2
    My advice would be go with 24v/48 straight off and get at least 500ah of batteries @ 24v. I would go for small forklift type batteries as they can take a beating. 24/48v is cooler, less cooper required in cables, less voltage drop and its easier to expand. 500ah @ 24v = 12,000wh @ 80% discharged they will give 1500 cycles 4/5 years (ISH) @ 20% discharge daily expect up to 15+ years if you get a auto watering battery system and they get a full charge most days. I would aim not to deplete the batteries more than 20% daily which translates to no more than 12000 dc watts/5 = 2400 dc watts DAILY USABLE AIM. If there is a cloudy week and you use 40% of the capacity of the batteries its not going to do them any real harm.



    The main thing about most lead acid batteries is they like to charged to 100% capacity at least once 2/3 few days if possible daily. If money is a bit of an issue over spec on solar panels and get cheap batteries to start with. At a later date you can invest in some newer batteries when you need them say 2/3 years down the line. In my opinion and quite a few others for any serious power input/output to cost/heat/efficiency ratio either a 24v or 48v battery system. Personally I'd go for 48v but you would get away with 24v no problem. I would get at least 1kw of solar input without question. Calculate it by your worst days not the best days. That way you wont run out of power ;)

    1kw of solar = 4 x 250w panels.
    Typical 250w panel = 30.67v x 8.13amps
    24v battery system wire them 2 x series connections 2 x parallel connections = 61.34vdc @ 16.26amps
    48v battery system wire them 4 x series connections = 122.68v @ 16.26amps

    Use min 6mm wire from solar to charging panels = 2-5% loss 5m-12m respectively.

    10-20% for efficient loss charging amps in to usable amps out for battery chemistry/heat/gassing loss

    To charge them I would ONLY get MPPT Outback FM60/FM80 or MPPT Midnite solar classic 150.

    Then its job done for a while :)

    I noticed you mentioned about capacitors and what not... I've done some experiments with them, I wouldn't bother wasting your money unless you want to play around with them, lol

    This is all in my opinion of course.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    rodney757 wrote: »
    I plan on using 6v batteries. Which are 207ish aH each. Thus I will either need 4 batteries or just go with 2 and run the generator a bit more.
    <snip>
    Should I run 12v or 24v?
    Welcome to the forum Rodney,

    IMO there's no doubt about it... go 24 volts. That means you will have the capacity you need (4 batteries) without making parallel connections.

    Your plans to convert a chest freezer to a fridge make sense, but you may need a larger inverter than 800 watts. Larger inverters have higher tare losses... your inverter may draw more than your fridge every day.

    You will wish to run power tools at some point... get a Honda eu2000 generator. It will be able to charge your batteries and power your house at the same time. You will be able to run a vacuum cleaner or a small air conditioner. They are very efficient, even when used at low power.

    By the way, what are you doing for water and water pumping?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • lkruper
    lkruper Solar Expert Posts: 115 ✭✭
    rodney757 wrote: »
    Hello,

    I am trying to design a system for our off grid yurt. I am hoping to run my computer for 4-5 hrs a day, a Danby 7.1 cu ft. converted chest fridge, and a few lights. I am estimating that I need about 150wh/day for the computer, 250wh/day for the fridge, and 100wh/day for misc. So it seems I need 500wh/day not factoring in efficiency losses.

    I believe I've seen 85% efficiency for inverters. If so, I will need 588 wh/day of battery storage. So for a 12v system, this would be 49 aH/day. With a 50% discharge and 3 day reserve, I would need about 284 ah battery bank.

    I plan on using 6v batteries. Which are 207ish aH each. Thus I will either need 4 batteries or just go with 2 and run the generator a bit more.

    I found the following information regarding sun hrs for my area. http://rredc.nrel.gov/solar/pubs/redbook/PDFs/OR.PDF. It seems like Nov-Feb I am definitely going to need use a generator. However, the fridge won't be as necessary as the temps are cool enough outside to use an ice chest if needed.

    We have access to grid power about 1/2 mi away at my in-laws where we will keep a freezer and can use larger shop tools when needed.

    I'm hoping to get a little help figuring out what I would need for my system. Should I run 12v or 24v? Is it better to run to generator a bit more or the get more batteries and panels? How do I determine what size array I need? What about the inverter size (800w?)? How about sizing the generator?

    Also, there is a Honda ev4000 RV generator on craigslist for $400 with approx 900 hrs on it. My feeling is that this will be a bit oversized for what I need. Do you think I will be better off getting a honda eu1000/2000 generator? Or is the fuel consumption not that different. It would be nice to run a small a/c for 10 - 20 days in the summer, but that isn't necessary.

    Thanks in advance for any help.


    Do you have bears? If so , I would not store food outside. They will make short work of a cooler. Here are some numbers to consider:

    Your lowest insolation value in winter is 1.38, according to www.gaisma.com. If we use a 1.5 fudge factor for your load that brings the total load to 1764. Based on the insolation you will need at least 1278 w for the panels. Based on that output it is recommended to go with a 48v system. With 5 day autonomy you would need 123 AH @ 48v. Because of the large panel size needed for winter, the charge rate is C/5. This would require you to use AGM batteries. You could instead raise the battery bank size to 221AH @ 48 volts with FLA batteries and get 9 day autonomy.

    Or, you could scale for your summertime insolation value of 6.42 and get by with a 300w panel and 490AH of battery capacity @ 12v and use the generator when your capacity falls off in winter months.

    Or you could size somewhere in the middle.




  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    lkruper wrote: »
    you will need at least 1278 w for the panels. Based on that output it is recommended to go with a 48v system. With 5 day autonomy you would need 123 AH @ 48v. Because of the large panel size needed for winter, the charge rate is C/5. This would require you to use AGM batteries. You could instead raise the battery bank size to 221AH @ 48 volts with FLA batteries and get 9 day autonomy.

    Or, you could scale for your summertime insolation value of 6.42 and get by with a 300w panel and 490AH of battery capacity @ 12v and use the generator when your capacity falls off in winter months.

    I think a 48 volt system, 5 days of autonomy, and AGM batteries are all inappropriate for the system that Rodney needs. A smaller system, with generator use when needed, will be far more cost effective. In particular I would warn Rodney to aim for 2 days autonomy (3 at most), no matter what voltage he chooses.

    490 ah at 12 volts is the same energy as 245 ah at 24 volts, and the 24 volt system is more appropriate (and more efficient) for his needs.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Just to think outside the box... Very roughly, it would cost you around $1,500 (or even less if you shop around) for 2,500 feet of copper 8 awg buried cable.

    You could pull around 2 amps @ 120/240 VAC (less than 3% voltage drop) and run 480 Watts of AC battery charging... You could forget the AC genset (except as pure backup power) and possibly even the solar panels (11 kWH of charging energy per day).

    Use the batteries+AC inverter for local 120 VAC power (batteries let you get enough power for surge current and some backup power if your utility power is unreliable in winter storms, etc.).

    You could add solar power, if you want to be a bit greener. And don't worry about the genset except for multi day power outages.

    Or go ahead and lay some heavy aluminum cable and bury or string on poles (or even direct bury). Roughly 2,500 feet of 2 AWG aluminum would cost $3,200 (Home Depot pricing) and you could run a 120/240 VAC service for 5-6 amps. You might get some irritating lights blinking when the refrigerator starts--But you could probably live a pretty nice life without any solar/battery/etc. power at all if you choose too.

    The laptop will not care, and if the lights blinking are too much after awhile--You could always use a 120 VAC to 12 VDC power supply (to buffer AC line voltage) and run 12 VDC lighting (desk lamp, critical lighting). You can try several brands/models of LED lighting--Some will probably be less susceptible fo "flickering" than others.

    Solar+Batteries+Generator are nice when you have no power available--But if you can get enough utility power to your home without using batteries+genset--I would seriously think about it.

    To test such a system--You could buy ~200 feet of 14 AWG copper 3 conductor+ground Romex (roughly $65 for 250 feet) to simulate a 2,500 foot 2/2/2 AWG aluminum service and run your 5-6 amps loads (chest freezer, LED lighting, laptop) and test it before committing to running service to the Yurt.

    Yes--This is a solar forum... But I like to look at the best solution for your needs and not push one solution over another.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    BB. wrote: »
    Just to think outside the box... Very roughly, it would cost you around $1,500 (or even less if you shop around) for 2,500 feet of copper 8 awg buried cable.

    That may make cost-effective sense (why didn't I think of it?). Of course, to recommend that solution I would need to know if the line crossed any roads or other people's property.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • lkruper
    lkruper Solar Expert Posts: 115 ✭✭
    vtmaps wrote: »

    I think a 48 volt system, 5 days of autonomy, and AGM batteries are all inappropriate for the system that Rodney needs. A smaller system, with generator use when needed, will be far more cost effective. In particular I would warn Rodney to aim for 2 days autonomy (3 at most), no matter what voltage he chooses.

    490 ah at 12 volts is the same energy as 245 ah at 24 volts, and the 24 volt system is more appropriate (and more efficient) for his needs.

    --vtMaps

    That makes good sense. One thing, I may not have used the term "autonomy" correctly. The template that I used (from another solar forum) multiplies the load by 5X to get the battery bank size. At 50% DOD that would really be 2.5 days of power before reaching 50%. However, the daily kWh was also multiplied by a fudge factor of 1.5 to account for all the other inefficiencies. So, what autonomy would that really be?

    The 48 volts is driven by the size of the solar array needed in winter. I understand it is common practice to rely on a generator in the winter. However, if I was living there full time, I am not sure I would want to listen to it at night.
  • kaipo_boy
    kaipo_boy Solar Expert Posts: 143 ✭✭
    We have no bears, but I'm still hoping. The rifle is loaded and waiting... :) just kidding. We got no bears in hawaii, but one can always wish. Old hunting habits die hard :)
    I have a 14.7 cu ft freezer converted for fridge use and the measured draw was .500 kwh per 24 hour period and that is in hawaii, with about 85F ambient temps. I have heard of people with similar freezer-turned fridges getting by with .200 or .300kwh in colder areas, which makes sense. My chest freezer, on the other hand, draws near 1.4kwh in a 24 hour period. And yes, it is a mild challenge going from vertical storage to horizontal but you get used to it. It is harder for women, though, as it requires bending over and reaching deep down to get stuff on the bottom, which is hard for short women. My significant other can't reach the bottom, so that's where I hide the cookies. Most days I can harvest enough sun to keep my 4x GC2 6v Interstate batteries charged pretty good (24v bank, 208ah). If the bank is full or nearly so, at night the fridge and freezer combo together will draw the battery bank down to near 75% SOC by dawn. That amount is easily recoverable the next day if weather is good, so it means I have nearly 2 days of reserve capacity with my 4 batteries, if that helps you. But I have no other loads on the system. I tried running my TV off it, but the older Sony 55" flatscreen drew something like 350w while on, and it required another box (PS3) to feed it a signal, another 80w or so, so just to watch netflix required close to 450w... so this week I sprung for a new 60" flatscreen.... its draw is something like 70w and it does not require another 'box' for signal source, it has a wireless receiver built in. Awesome.
  • rodney757
    rodney757 Registered Users Posts: 4
    Wow. Thanks for all the replies.

    So the closest power would be just under a 1000' run. This is all on the same property. I would just need to cross a creek (there is a nice bridge), an old logging road that we use maybe 3-5 times a year and go up some fairly steep forest area. The cows get put in the forest for maybe 4wks per year total.

    It seems like this may be the best option. While I like the ideals behind solar, it seems like it's not very practical in my location unless there's not other option. What would be the best way to run the cable?
    Thanks again for all the discussion. It's been really helpful.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    I am not a code person... So contacting a local electrician may be helpful (and you may need a building permit too).

    There are lots of ways/tricks to send power a 1,000 feet (use a transformer to pump the line voltage up to 480+ VAC and a second transformer at the Yurt to drop it back to 120/240 VAC, etc.). And if you are thinking of building a house eventually--Installing a well designed AC service with enough power for a modern home (based on your lifestyle) may be worth doing "right" once. Transformers do have losses--So you may want to think twice if you do not use much electric power (i.e., Yurt vs Modern Home energy usage).

    Running on poles--Easier, but leaves you with "ugly" power lines, possible damage from falling tree limbs, and even somebody stealing the wire (if you have problems in your area). If temporary, easier to remove later. Run telecom/Internet cable on poles too.

    Burying in ground--Protected from falling limbs, out of sight, harder for somebody to steal the copper/aluminum. Depending on the ground in your area, may be an easy or difficult dig. If you are already trenching--Did second trench for water/telecom+Internet, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    lkruper wrote: »
    ...... I understand it is common practice to rely on a generator in the winter. However, if I was living there full time, I am not sure I would want to listen to it at night.


    I had several months of nearly no sun, and just used the generator for about 60-90 minutes in morning, and some days, 60 minutes in the evening. No need to let it run all night. That's what batteries are for. If you run the generator in the AM, and bulk the batteries up to the absorb point, any sun that day can start and maybe complete your absorb cycle. Saves fuel to not generate all the way to Float.
    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 ,