small cabin solar system

mwarrenmwarren Registered Users Posts: 4
I am building a small cabin (16x16) at the back of my 35 acres of land.  The cabin will be used in the winter time as a warming hut when we are out sledding with the kids on the sledding hill (we live in Vermont).  We may occasionally sleep out there but our house is not far so we don't need it to have an elaborate power system.  I would like to be able to use a small LED television to watch an occasional football game or movie, possibly power a small radio to listen to music and I would like to power a few small LED lights that would be used at night.  The electric needs won't be any more elaborate than that.  If I need more power than that, I'll run my small generator. 

The location gets fairly good exposure to the sun for most of the day.  We would only use the cabin for a few hours, one or two days a week at the most. 

I have been looking online at the Renogy 200w solar starter kits.  I am wondering if this is the type of system that would work for my limited needs or if I would be making a mistake with something like this.  How many batteries would I need and what type would be best (6V or 12V?).  I think that I will wire the lights direct to the battery and use 12v LED lighting rather than running the lights through an inverter.  I was also thinking of using a 12v car stereo wired directly to the battery as well. I will only use an inverter for the television. 

Any thoughts?  I tried to search through the various forums for the answers to my questions but it seems that every systems needs are a bit different therefore I thought it would be best to ask specifically about my situation.  Thanks for any help and guidance you can offer. 

Mike 

Comments

  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    Every situation is different, but as a rule it always starts with loads and expectations.

    As a very general statement, IMHO a 200w kit would likely work for what I'm understanding your loads and expectations to be. Winter can be a challenge, but if you can charge with a generator you can get away with less pv, and occasional use allows for production to catch up with use. You will want to be sure the location for the panels gets full sun. Even bare tree branch shadows in a low winter sun can cut production to almost nil. In full sun though, cool temps and snow reflection can offset short daylight hours a bit. I'm also assuming the location for the panels will be fairly close to the cabin (within, say, 40' or so). If you have to go much further for full winter sun, the kit may not be the best choice.

    A pair of 6v deep cycle golf cart batteries in series would be a reasonable fit. This would give you ~100ah or 1200watt-hours of usable capacity. For long battery life, we avoid drawing a deep cycle battery down more than 50%, and want to get it charged reasonably quickly (next day or two) from there. Lower states of charge also risk freezing damage.

    If you intend to turn off for summer, a pair of 12v deep cycle AGM batteries in parallel might be a better choice. They may cost ~2x the price of flooded golf carts, but they tend to have much lower self discharge, and would likely stand up better to sitting over the summer.

    Realistic production from the pv in winter might be ~10-12a or 5% of the rated capacity of the batteries, which is low, but likely workable for a weekend type use.

    Hooking up a car stereo directly to batteries might seem more efficient, but the details matter. Some take significant power, and many draw power even when not in use. Not a big deal in a car used regularly charging with an alternator, but could be an issue, for example, if you shut the solar down for summer or whatever. I have one on my boat, and it will discharge the house bank over the winter if I don't disconnect it.

    I would use a small (~300w) pure sine wave inverter for the tv. Probably for the radio, and maybe the lights too. There's something to be said for just flipping the inverter breaker and knowing everything is off when you leave. A modified sine wave inverter would be cheaper, but may or may not run the tv, and even if it does, will likely run it hot.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • 706jim706jim Solar Expert Posts: 168 ✭✭✭
    Your whole show could run directly off of 12 volts. Many of the LED televisions run from an adapter that produces 12 volts DC from 120 volts AC, so you could just wire directly into the TV to run it that way. Note that some are 19 volts DC input so this approach may or may not work for you. I'd go with two 6 volt golf cart batteries wired in series. Your 200 watt panel will be able to charge these reliably and they aren't too heavy to carry to the cabin.

    Can you/should you get something bigger? Sure, but the above would work for what you are describing.

    One last thing: You can get a cheap 150 watt inverter (modified sine will be ok) to run a TV. This low wattage inverter can be plugged into those silly "cigarette lighter" sockets without overloading the circuit and would also be really cheap. I use one of these in my boat to run a TV with good results.

    Let us know what you end up with.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 24th year.
  • mwarrenmwarren Registered Users Posts: 4
    Thank you both for your comments. 

    We will actually use the cabin in the summer too.  We will use it less often but will still go out there to get away and enjoy the peace and quiet. My plan is to mount the panels on the side of the cabin facing the sun.  There are some "bare trees branches" that will block the sun a bit so I may just cut them down and use them for firewood to help open up the sun to the panels.  Mounting them on the cabin will allow me to have less wire between the panels and the batteries. 

    Would it be better for me to get 300w instead of 200w?  I am a bit uneducated when it comes to DC power and understanding watts/volts/etc...  Would it be better (if I was worried about not having enough power) to get more panels (like 300 or 400W) or would it be better for me to get more batteries (4 batteries instead of 2)?  Or should I do both?  I'd rather get what I need the first time, however I don't want to spend money unnecessarily to buy a bigger system than I actually need. 

    I like the thought of having everything wired up to 120v and running it off a pure sine inverter.  This way I can just wire up the cabin with 14/2 to run the lights, and a few outlets for TV or a radio.  I will just put a male plug on the end of the 14/2 and plug it into the inverter.  That way it I want to run them off a generator, I can just unplug from the inverter and plug into the generator.  Is this an ok way to do it?

    Mike


  • 706jim706jim Solar Expert Posts: 168 ✭✭✭
    Well if you are up to spending the money get a decent inverter and scrap the 12 volt wiring. I wired my place in 1992 when inverters were scarce and expensive. I did a dual system of 12 volts and 120 volts. The 12 volt system never got used mostly due to line losses.
    An inverter of 1500 watts capacity will run one of any appliance that can normally be plugged into a duplex outlet, such as vacuum cleaners, skil saws, microwave etc. And a true sine inverter will power pretty much anything whereas the cheaper msw inverter may cause problems with some appliances or chargers. A larger inverter will be happier with more batteries and panels.

    So maybe start with a budget and see what you are willing to spend. We could provide more specifics if we knew that number.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 24th year.
  • mwarrenmwarren Registered Users Posts: 4
    Is $1000 or less reasonable?  I was thinking of a setup like this? 

    https://www.amazon.com/Renogy-Complete-Monocrystalline-Controller-Inverter/dp/B075XG41G5/ref=sr_1_23?ie=UTF8&qid=1510542400&sr=8-23&keywords=renogy+200+watt

    Seems like it comes as a well balanced setup.  Battery and inverter are sized correctly for the size panels.  What do you think?

    Thanks, Mike

     

  • wellbuiltwellbuilt Solar Expert Posts: 188 ✭✭
    edited November 13 #7
    I've been living off 2 6volt gc battery's from sams club .
    i use a pro sine 300 watt inverter about 250watts of solar panel morning star charge controler 20 amp .
     This works real good auto 12 volt charger 10 /30 amp . 
     That's about it . 
     I set it up and it has been running since2014 , I had some trouble with my charge controler but I replace it with a 15 year old unit I had laying around .
     The battery's have been  losing  capacity but are still fine and last a few days with out sun . 
     I use a 32" Samsung tv burns 25 watts . 
     Makita radio with tools charged from the inverter . Draws 300 watt at start up but tappers off fast .
     Champion 1800 watt cheapie genarator . 
     I just run off the inverter with led lights . 
     I sleep with a C- PAC and the battery will drop to 75% this time of year. ( it was 17o sat night )
      I used this system in a old trailer  while I'm building a  off grid home . 
      Last night was the first night in the new house  I needed some heat . 
  • kansaskansas Solar Expert Posts: 97 ✭✭
    I have a cabin we use for roughly the same purposes you do.  We have lots of lighting, a DC motor ceiling fan, a small vornado fan, laptop, signal booster for the cell phone/ hotspot, etc.  After considering several options I ended up with the setup described in my signature line.  I decided on these components after working through the appropriate sections of Photovoltaics, Design and Installation Manual by the Solar Energy Institute and shopping at this site's sponsor - Northern Arizona Wind and Sun. You can gain a real understanding of how a PV system works if you start by breaking down your specific energy needs, the sun that is, on average, available in your area, the size and efficiency of the various system components, etc. I decided to purchase top line components, reasoning that a good system would last many years and would represent the great majority of the cost for many years of otherwise free solar power. Good luck - Bill

    Two 140 watt Kyocera panels, wired in parallel; Ironridge top of pole mount; two 6 volt, 242 AH US batteries, wired in series; Morningstar ProStar 30 charge controller and SureSine 300 inverter; Trimetric 2025-A meter; IOTA DLS-45 charger, Honda EG3500X generator; Aermotor 702 water pumping windmill.
  • 706jim706jim Solar Expert Posts: 168 ✭✭✭
    The system you quoted should work. I'd consider more battery storage (even two GC's) but this would be an inexpensive start.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 24th year.
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    Personally, I would get the kit sans battery, and buy a couple of flooded golf cart batteries locally - ~225 amp-hours @12v for ~$200. Probably work out to about the same price for over 2x storage.

    One important potential issue with the plan to me is switching a plug from inverter to generator. Hopefully the generator will be outside (CO could reach deadly levels in minutes if run in the cabin). I would wire to a generator panel to make it easier to install breakers.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,837 admin
    Just out of curiosity... To run 12 AWG 1,000 feet for ~$200-$300, rent a trenching machine (at lest 18" deep--check local code--tree roots and rocky soil--not so much fun). Will give you 1 amp @ 120 VAC pretty reasonably ~3% voltage drop (120 watts--TV, some LED lighting, a box fan during the day). No batteries, shade/weather, etc. to worry about.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • wellbuiltwellbuilt Solar Expert Posts: 188 ✭✭
    I just run off the inverter most of the time. 
     My auto battery charger is hook to the genarator only . 
     So I charge and invert at the same time. 
     But I don't really have to use the genarator much . 
     I would charge with the inverter off most of the time when we where out not using  power .
  • softdownsoftdown Solar Expert Posts: 1,531 ✭✭✭✭
    BB. said:
    Just out of curiosity... To run 12 AWG 1,000 feet for ~$200-$300, rent a trenching machine (at lest 18" deep--check local code--tree roots and rocky soil--not so much fun). Will give you 1 amp @ 120 VAC pretty reasonably ~3% voltage drop (120 watts--TV, some LED lighting, a box fan during the day). No batteries, shade/weather, etc. to worry about.

    -Bill
    I'd look at this idea closely. Reliability, economy, simplicity, and resale value may enter the picture.

    One giant problem with batteries is their limited lifespan. The years fly by and the batteries die off. Lots of connections with solar as well. Perhaps you like challenges?
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 150 watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • mwarrenmwarren Registered Users Posts: 4
    I'd love to just run a power line out to the cabin.  I have to cross three small streams (one with a 30 foot deep ravine), and run through woods the entire way.  I think my property has 10 Billion rocks on it so trenching would be almost impossible.  I suppose I could use direct burial cable so it is a bit more protected from the elements and just run the line on top of the ground (no different than running an extension cord...).  Is it really reasonable to think that running a 12awg wire 1,000 feet from my panel will work?  I know VERY little about electricity!!!  Any thoughts?

  • mcgivormcgivor Registered Users Posts: 1,280 ✭✭✭✭
    @mwarren asked,  Is it really reasonable to think that running a 12awg wire 1,000 feet from my panel will work?  I know VERY little about electricity!!!  Any thoughts?

    With that gauge and distance, the maximum current, to stay within  3% volt drop would be approximately 1 amp, assuming copper and 120V, so not really practical  
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • softdownsoftdown Solar Expert Posts: 1,531 ✭✭✭✭
    mcgivor said:
    @mwarren asked,  Is it really reasonable to think that running a 12awg wire 1,000 feet from my panel will work?  I know VERY little about electricity!!!  Any thoughts?

    With that gauge and distance, the maximum current, to stay within  3% volt drop would be approximately 1 amp, assuming copper and 120V, so not really practical  
    A critical measurement may be the existing voltage that he would be tapping from. Could easily run from 123 volts down to 112 volts.

    Assuming 120 volts, he would be OK with 110 volts at the cabin. I believe that equates to having 3 amps available at the cabin.

    "Is it really reasonable to think that running a 12awg wire 1,000 feet from my panel will work?"  You need to be careful when using the word panel around here. We think of solar panels.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 150 watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    Might be worth pricing out aluminum locally. It needs to be sized up a gauge size, but it might still be cheaper.

    My diesel used to be 6-800' away from the cabin with similar terrain. It was connected with 6ga aluminum for 30a@120v output. They just strung it overhead with ceramic insulators screwed into trees. I moved the generator (wasn't wild about 250gal of diesel at lakeshore, and scrambling down a cliff to get at it was getting old), but it apparently worked fine for > 30yrs.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators Posts: 26,837 admin
    I have to leave it to you about if you want/can run cable from your home to the cabin. The 1,000 feet of 12 awg was just an example of power and costs to (possibly) get a little power to the cabin without the hassles and costs of solar.

    If you need/want more power--Go to 10 or 8 AWG (copper or heavier aluminum) and string 2 hot + 1 neutral + 1 ground (ground may not even be needed)--And you can easily get more power to the cabin (just going from 120 to 120/240 VAC can get you 4x the wattage with the same AWG cable).

    If solar still makes more sense--Then go for it. It will take maintenance to keep it going (checking electrolyte levels in batteries, cleaning, new batteries every 3-5 years or so--cheap golf cart type, trimming trees from shading panels, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 1,531 ✭✭✭✭
    1000' is a lot of real estate. I might consider charging a couple golf cart batteries, as needed, with a genset. 

    They could supply 1 amp of 120 volt power for quite awhile. Over time, you may get a better idea of your power needs. 

    I have bought plenty of things thinking I was going to use the heck out of it. The only thing I really use a lot....is my reclining chair and my boots.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 150 watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • mcgivormcgivor Registered Users Posts: 1,280 ✭✭✭✭
    edited November 17 #20
    mwarren said:
    I'd love to just run a power line out to the cabin.  I have to cross three small streams (one with a 30 foot deep ravine), and run through woods the entire way.  I think my property has 10 Billion rocks on it so trenching would be almost impossible.  I suppose I could use direct burial cable so it is a bit more protected from the elements and just run the line on top of the ground (no different than running an extension cord...).  Is it really reasonable to think that running a 12awg wire 1,000 feet from my panel will work?  I know VERY little about electricity!!!  Any thoughts?




    One method to cover the 1000 foot distance using smaller conductors would be to use a trasformer at each end, example a step up from 240-480V at the feed end and step down at load end, 480-240V  with a center tap transformer to provide 120V , using 8 AWG copper or 6 AWG aluminum,  10 amps at 480V or 20A at 240V  would be possible to be below 3% volt drop. The conductors would have to have insulation rating higher than the voltage used eg. 600V, no comment on how the conductors should be run.

      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • Bradley45Bradley45 Registered Users Posts: 1
    edited November 17 #21
    wellbuilt said:
    I just run off the inverter most of the time. 
     My auto battery charger is hook to the genarator only . 
     So I charge and invert at the same time. 
     But I don't really have to use the genarator much . 
     I would charge with the inverter off most of the time when we where out not using  power .
    Will this really help in saving the power used?I am thinking to do the same.I come from a place where most of the year, we have good sunlight.So thinking to make use of the solar energy well.And i m new in knowing and using the solar energy, but I am very interested, as it saves money and also protects nature.
  • BB.BB. Super Moderators Posts: 26,837 admin
    Off grid solar is generally not "green" for the sake of being green. It is because it is at least as cost effective and much more quiet than running a genset. (call it ~$1.00-$2.00 per kWH if you include hardware, new batteries every ~5+ years, $3.00 a gallon genset fuel, etc.). Compared with $0.10 to $0.40 per kWH--Depending on your local rates.

    Solar panels and lead acid batteries when manufactured are not really green. However, recycling of lead acid batteries is pretty green (most lead acid batteries are built from recycled batteries). However, the scrapping yards have been known as toxic waste sites (not unlike many other modern mfg activities--not picking on batteries specifically).

    In general, doing everything you can for conservation (double pane windows, lots of ceiling and wall insulation, summer shading of building, energy star appliances, LED lighting, turning stuff off when not in use, etc.). That will save money in the long term.

    Energy usage is a highly personal set of choices. Asking question, doing research, and even some paper designs of different solar power systems and conservation projects--All a good start. We aim for practical solutions that work for you. What works for me (Grid Tied Solar) in a moderate Climate (near San Francisco, California) may not work for you in India.

    Most people that have utility power that is unreliable (afternoon power outages)--Set up battery bank+AC inverter to carry them through 4-8 hour outages instead of noisy backup generators. The battery bank can be recharged by AC mains (once the power is restored)--Or for not that much more money, add solar panels to save money on the utility bill and support multi-day outages without (or less use of) a generator. Remember that even if you have a nicely running battery system--It is easy to "murder" your battery bank if something goes wrong (somebody forgets to turn off the electric tea kettle, leaves a hair drier running, kids leave all the lights and TV and computers running and take the battery bank dead). I do not see off grid/hybrid solar power systems as saving money--And it is debatable they are "greener" than utility power+conservation. And when something fails, you need to buy parts and fix the system to get it running again.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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