Mountain Cabin - New to this!

Greg_Salyer_13
Greg_Salyer_13 Registered Users Posts: 11 ✭✭
edited May 2016 in Solar Beginners Corner #1
I want to install a solar system at my remote mountain cabin. It has no electricity at all.

Here is what I want to run....

(6) 100 watt equivalent LED Light Bulbs (17 watt actual) 
(4) Window Fans
(1) Dorm Fridge

My calculations show with everything running I would be using about 400 watts and about 3.5 amps. I know the fridge will also spike on startup. The cabin is typically only used for a 3 to 4 day stay about once a month.

I also have (2) 12v water pumps used intermittently rated at 7.5 amps (these are 12v)

I am looking for recommendations on a solar array and battery bank requirements. 

Thanks!

Comments

  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    edited May 2016 #2
    Welcome to the forum.

    You have what I call a 'defining load'.  That means you have one load, the fridge, that will define the entire system.  The fridge moves you from a small system to a medium sized system.  

    Dorm fridges are notoriously inefficient, but even if efficiency was not an issue, the startup surge is an issue.  It means that you need a larger inverter.  A larger inverter has higher tare losses.  My 3500 watt inverter uses 20 watts by just being turned on.  That's very good for an inverter of that size, but it is also 480 watthours per day... almost as much as my ultra efficient fridge uses.

    You should consider investing in a more efficient fridge.  Sure it will cost money, but it's going to cost you something to build a larger power system just to run that dorm fridge.  If not for that fridge, a Morningstar 300 watt pure sine wave inverter would be a good match for you.

    Anyway, to get back to the question you asked, you did not provide enough info to answer... I need to have a number... kilowatthours per day.  You mentioned 400 watts with everything running... that's 9.6 kwh per day if everything is running for 24 hours.  That will require a huge system!  Of course, everything is not running all the time, but you haven't told me just how long they are running.

    Are you planning to leave the fridge running when you are not at the camp?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    Lights only in the evenings, say 4-5 hours a day.

    Fans will run all night when it is hot.

    The fridge would only be running when we are at the cabin. I searched for an ultra efficient fridge and came up with this: 
    Whynter FM-62DZ.
    Voltage power AC (115V/60-Hz - 0.8A) or DC (12V/24V - 4.5A/2.5A )
    Wattage: 65 Watts

    It has a $600 price tag but that is not out of the question if it is really worth it, however it seems (at least on paper) to have about the same power requirements as a $100 dorm fridge.

    Thanks!
  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    The nice thing about that Whynter is it can also run direct off 12 or 24 VDC. That avoids the need for a (bigger) inverter. 

    With that in mind you might consider keeping everything DC; 12 VDC LED lights are easy enough to find. 
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • Thom
    Thom Solar Expert Posts: 196 ✭✭✭
    small inverter 400w morningstar  120v DC ceiling fans . It's nice to have 120v AC 
    Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator . Added 2@ 100w panel with a midnight brat 
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    I only see morningstar in the 300w
  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    I want to install a solar system at my remote mountain cabin. It has no electricity at all.

    Here is what I want to run....

    (6) 100 watt LED Light Bulbs

    Are those really 100 watt LED light bulbs or are those LED bulbs equal to a 100 watt incandescent light bulb?
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    LED bulbs equal to a 100 watt incandescent's (17 watts actual)
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    It has a $600 price tag but that is not out of the question if it is really worth it, however it seems (at least on paper) to have about the same power requirements as a $100 dorm fridge.
    Same power requirements as the dorm fridge?  Where are you seeing that?  

    As I mentioned earlier, it may be worth paying more for two reasons... lower energy use, and DC operation.  The DC operation means you don't need to run any inverter.   Even the little morningstar has some tare losses.   The lower daily energy use means you need a smaller battery and less solar panels.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Thom
    Thom Solar Expert Posts: 196 ✭✭✭
    I only see morningstar in the 300w


    thats the one . I have used one for a few years. 

    Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator . Added 2@ 100w panel with a midnight brat 
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    edited June 2016 #11
    I ended up getting a good deal on a gas fridge so my requirements now are only...

    (6) 100 watt equivalent LED Light Bulbs (17 watt actual) 
    (4) Window Fans

    My calculations show with everything running I would be using at the most 286 watts / 2.36 amps. This is a high estimate on the fans based on some info I found online. I am going to test one with a Kill-A-Watt Meter tonight.

    The cabin is typically only used for a 3 to 4 day stay about once a month.

    I am looking for recommendations on a solar array and battery bank requirements. 

    Thanks!
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Used 12 months of the year?  How much use in the 'depths' of winter?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    I actually love going in the winter. About the same, 3 to 4 day stay about once a month.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    edited June 2016 #14
    so what time of the day does the sun strike your panels?  Mine start to put out enough voltage and Amps to start charging  at ~ 11:45 and go to ~ 2:00 on Dec 20 so a bit more than 2 1/4 hrs...  I am way over paneled for the summer, as I hit Absorb by 11:30 and we have 21 days to go till the longest day...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    so what time of the day does the sun strike your panels?  Mine start to put out enough voltage and Amps to start charging  at ~ 11:45 and go to ~ 2:00 on Dec 20 so a bit more than 2 1/4 hrs...  I am way over paneled for the summer, as I hit Absorb by 11:30 and we have 21 days to go till the longest day...
    I don't know. The cabin is located in the tip of SW Virginia.

    I don't have any panels now. I am at the planning stage. I want to do it right the first time. 
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    the obvious is to locate a spot that gets as much sun as possible.... Once I thought I had a good spot  I took pictures every 1/2 hr and studied them back home, verified where I thought it should go and placed a marker in the ground and then rechecked it in the winter, that is the time that your exposure to the sun is critical....  be observant of ANY shadows from deciduous tree branches, one shadow can kill over half of a panels production...  a few trees have disappeared in the last few years... February was hard on them!
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    My calculations show with everything running I would be using at the most 286 watts / 2.36 amps. This is a high estimate on the fans based on some info I found online. I am going to test one with a Kill-A-Watt Meter tonight.

    The cabin is typically only used for a 3 to 4 day stay about once a month.

    I am looking for recommendations on a solar array and battery bank requirements.
    You still haven't provided us with a kwh per day number.  I will run through the rule-of-thumb formulas based on the assumption that it is winter (no fans) but that your lights are on 10 hrs per day.  Six lights at 17 watts each, on for 10 hours, is 1020 watthours (about 1 kwh) per day.

    Since it's winter, you can't count on getting much sun every day.  Let's say you want your battery to supply 3 days of energy without dropping below 50% SOC.  In that case you need a battery capable of storing 6 kwh of energy.  A 12 volt battery with that capacity is 500 ah.  (12 volts X 500 ah = 6000 watthours)

    Since you will have a month to recharge the batteries, you can probably get by with a minimal solar array that would provide a 5% charge rate.  5% of your battery's ah capacity is 25 amps.  In order to get 25 amps at a charging voltage of 14.4 volts, you need 25 amps x 14.4 volts = 360 watts going into the battery. 

    In order to get 360 watts going into the battery, you need about 400 watts going into the controller (assume MPPT controller is 90% efficient).  Under typical summer conditions the panel wattage must be derated because they are hot.   In the winter, the colder panels may put out closer to their nameplate wattage... if they can get enough sun.  The sun being low in the sky lowers the insolation.  You probably need 450-500 watts of panels.

    I have made a lot of assumptions and I haven't done any calculations for summer when you use the fans more and the lights less... your thoughts?   By the way... do you have a generator?  If so, you could really shrink your battery bank.  On days when it's not sunny, run the generator for a couple of hours.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    I do have a generator and we have natural gas (free due to a gas well on our property), however I hate the noise of a generator. I also just did a quick search for a standby inverter charger which I assume is what I would need and it looks like that would set me back $900 to $1500. Any cheaper way to add a generator to the setup?
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
     Any cheaper way to add a generator to the setup?
    If you need an inverter, then an inverter/charger is the way to go.  If all your loads were DC (no inverter), then you could use a battery charger powered by the generator.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Greg_Salyer_13
    Greg_Salyer_13 Registered Users Posts: 11 ✭✭
    edited June 2016 #20
    I bought a Kill-A-Watt meter and checked one of my fans. On high it pulled .06 kwh in 1 hour (60 watts). I used the calculator on this site and it looks like I would be using a max of just under 3,000 watt hours per day about 4 days per month. This is assuming all 4 fans running 10 hours per day on high which would rarely happen. Low = 40 watts, Med = 50 watts.
  • vince
    vince Registered Users Posts: 79 ✭✭
    If you only have lights and fans, look into using only DC LED lights and fans. An inverter may use more than your load combined on standby not to speak of the purchase price.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    If you stick with 12 VDC, here is one thread discussion DC window fans:

    http://forum.solar-electric.com/discussion/10865/most-efficient-12v-dc-fans

    Here is one discussion about Ceiling Fans:

    https://forum.solar-electric.com/discussion/9774/dc-ceiling-fans-worth-it

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Beware of the simple watts test of the fan and LED/CFL lights.   They have poor power factor, and off-grid, you need to have a 50% larger inverter & generator to run them.   The kill-a-watt meter HAS both PF test and VA test so you can see how bad it is.
    The link below - goes to a page that explains this, and there is a you tube video too.

    http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorFluorescent Lights with Electronic Ballasts

    https://www.youtube.com/watch?v=LeCqreRMzKM





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