New to solar, a few questions

rhine
rhine Registered Users Posts: 10
Hi, I am trying to get power to a shed that cannot get power from the lines. What i would like to power would be 4 or 5 light bulbs and a small dorm style mini fridge. I found a starter system from northern and i was wondering if this one would do all of this. thanks in advance. http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200352703_200352703 also i plan on having 2 or 3 deep cycle batteries with at least 100 amp hours possible the D31m from optima http://www.optimabatteries.com/optima_products/bluetop/specs.php thanks in advance.

Comments

  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    Re: New to solar, a few questions

    Welcome Rhine,

    I don't think the system shown in the link that you provided will do the job for you. It might, but first you have to analyze your electrical consumption very meticulously. Decide on four or five light bulbs. Then decide what their wattages are going to be. Then try to estimate how long each of them will be in use in a 24 hour period. Then find out the power consumption, in watts, of your refrigerator, which I asume will be in use 24/7. The goal is to determine your total consumption in Watt-Hours (the same quantity your power company uses to decide how many dollars you owe them.) Once you know this you can determine how much PV you need. I assume that all of the devices you intend to use are 120VAC. For this you will need an inverter which introduces inefficiencies thereby requiring even more PV power.

    I can tell you that 60W of PV will not run a 120VAC refrigerator 24/7.

    Other great members of this forum may chime in with more suggestions

    In the meantime, as an example, I suggest that you look at the link in my signature about My Solar Camper Project to see how I have estimated my power consumption.

    Enjoy!
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: New to solar, a few questions

    The "dorm style" mini fridges use nearly as much power as 22CF energy star fridges. Beware of them (mini-fridge) Count on a fridge consuming about 1,000WH daily, depending on how efficient it is.

    Also, beware of Northern Tool, for long life solar, you get lots of little panels, lots of interconnect wires, and generally, after a couple of years, lots of problems. Northern will likely say, we don't stock that, here's the mfg's phone in china. A dashboard panel for your car, fine, but not house power.
    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 ,

  • Chui
    Chui Registered Users Posts: 7
    Re: New to solar, a few questions

    Kamala offers good advice. Something to keep in Mind is that it takes heat to make things cold (just feel the condenser on your fridge) and it takes a lot of energy to make things hot. Good truely energy efficient fridges are quite expensive. One of the best values are the SunDanzer fridges. Their smallest would be bigger than a dorm style fridge, but very efficient.
  • rhine
    rhine Registered Users Posts: 10
    Re: New to solar, a few questions

    Hello, thanks for all of the responses, from the answers i'm getting maybe this would be a better question to ask. This shed that I am hoping to power will be mostly used on weekends sometimes three days a week. I would like to be able to run 5 lights but they should only be used at most 1.5 hours a day for at most 2 to 3 days a week. I am not going to be there every weekend but from september to december it will be most weekends. This will be located just south Little Rock AR and should receive good sunlight throughout the day.

    Now on to the Mini fridge, this is something that would be very nice to have there to keep food fresh and drinks cold. would it help not being there much and knowing that the door will not be opened much? the mini fridge that i already have says on the back that it is power supply 120 volts, 60 htz. and imput current is 1.2 amps.

    so now if somebody could please help me determine a system to use and how many batteries to use and how big of an inverter to use. I really apprecieate how helpful people are on this site and thanks in advance for any imput.

    Rhine.
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: New to solar, a few questions

    Ouch. Your fridge pulls more amperage than my full-size fridge! And I'm betting my full-size one has more insulation (thicker walls) than the dorm fridge does, so may even run less time in a day than it would. My walls are larger (more surface area) so maybe not. At any rate, my fridge is (supposed to be) a pretty efficient one and consumes about 1.6kWH per day (measured with a Kill-A-Watt meter) and I once figured up what I would need battery bank / solar wise to keep it running 24x7. That was a painful number!

    I currently have four 135W Kyocera panels (good name, a far cry better than Northern Tool or Harbor Freight are going to provide) and an Outback MPPT charge controller, and could *probably* keep up with *JUST* the fridge during the long summertime days. I can NOT keep up with it in the winter months. Any clouds at all, and I won't keep up in summer either. (Note I don't use the system for this - it is primarily for other things, but could run the fridge if the power is out, getting some charging help from a generator when I'm home.)

    That's a lot of money for a weekend party shack! (Just the items above, self-installed, ran over $2800, we haven't even talked about the battery bank, inverter to plug the fridge into, and other associated components!) You could buy a LOT of ice for the cooler before paying for a system that can keep a fridge going. Or buy a small inverter generator (Honda or Yamaha make nice ones) that sips gas and is very quiet, and use it to run things when you are there.

    Now, if you cut out the fridge you are talking about a MUCH simpler system! In fact, a 45W "kit" from HF or Northern Tool could probably keep up with your projected lighting usage. Note my calculations below don't factor in a bunch of losses. There are some losses at each step, and some factor in a lot more than I would!

    Assumptions: 5 20W CFLs, 4.9 hours wintertime insolation (that's mine, in OKC - yours would actually be a bit less I think), 12V system

    5x20W = 100W load x 2 hours/night x 3 nights = 600WH per week total load

    600WH / 12V = 50AH per week

    So, if you are willing to draw the battery down close to 50% discharged (not really desirable on a regular basis, but not a huge deal weekly) you could use a 100AH or so battery. Better would be only going to 25-30% (less stressful on the batt, gives you some reserve) which could be done with two 6V golf cart batteries in series for a roughly 220AH bank.

    4.9 hrs insolation x 7 days/week (we get sun on the weekend between each use too) = 34.3 hrs

    50AH / 34.3 hrs = 1.46A the panel(s) need to provide while charging. Or, 17-18W.

    Note that solar panels are rather optimistically rated. My 135W Kyoceras are "realistically" rated at 95W (the PTC rating) and my original Harbor Freight 45W panels do good to hit 20-25W! Better brands will provide the PTC rating, which is a safer number to use. Some people just derate 50% and be VERY safe!

    So, a 25-30W "good" panel, or a Harbor Freight "45W kit" would just be able to keep up with this. Assuming no cloudy weather! You may want a bit more to overcome that, if it's critical.

    Also keep in mind, loads generally go up over time. Might want a radio or TV with you. Or some other appliance. You may want/need to upsize again to anticipate some of those.

    For just lights, pretty much any inverter would do. I have found my CFLs emit a slight buzzing on mod-sine inverters, not terribly annoying unless I'm close to the bulb. They are silent on my pure-sine, but those are pricey just to run lights... Size-wise, just get one that can handle the loads. Don't go overboard, as the inverters have a certain power consumption themselves and the larger they are (generally) the higher the consumption.

    Hope that makes sense...! :p
  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    Re: New to solar, a few questions
    For just lights, pretty much any inverter would do. I have found my CFLs emit a slight buzzing on mod-sine inverters, not terribly annoying unless I'm close to the bulb. They are silent on my pure-sine, but those are pricey just to run lights... Size-wise, just get one that can handle the loads. Don't go overboard, as the inverters have a certain power consumption themselves and the larger they are (generally) the higher the consumption.

    For just lighting go with 12 volt CFL's or better yet 12 volt LED lights. This will alleviate the need for an inverter and may allow for a smaller battery bank.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New to solar, a few questions

    thinking about what i would probably do in that circumstance would be to use an inverter generator. good on gas and plenty of power for those weekend getaways. if you don't want to run the generator at night, but still need power then the battery/inverter thing comes into play for those quiet times and the battery(s) could be charged by the generator and a good 3 stage charger. if you don't wish to take the batteries with you during those long winter months they will need to have a small maintenance charge to them. this is where a pv and a controller can maintain the batteries and this allows for a smaller wattage pv to be used because the batteries main power source during occupation is not the pv, but is the generator. i'd pick a pv with a current output somewhere around 2-3% of the batteries' capacity in amp hours, but can be more to cut back generator needs too.
    a refrigerator will draw alot of power as the guys mentioned and if you need to have as per example 1600wh for the frig per day and say another 300wh for lights, this is 1900wh. efficiencies may up this need by 30-40% and if relying on pvs it may need upped even more so 2500-2600wh could be typically needed for just a small frig and a few small lights. this can be done by all solar if you divided the typical 24hr power need in wh by the number of full sun hours received in a day to roughly give the wattage in pvs required to minimally run things. more may be needed for reserve and cloudy times and is why i'd opt to charge batteries primarily by generator and use pv to maintain the batteries during those long periods of absence.
    one more note here on the generator as it will need to run things while also charging batteries for those off times, then this will up the wattage requirement of the generator to that of both your ac loads and the battery charger load requirements. knowing the top draw of all items on the generator at once is necessary so that you can keep generator runtime down.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: New to solar, a few questions

    Get a small Dometic Under the counter RV Propane fridge. You should be able to find one in a RV Junk yard almost free in good running condition. (The last one I got I found in a wrecked truck camper at the dump! Works great,, has for years!) You also might find a full size RV fridge pretty cheap if you do some searching.

    You can run one on a bbq tank,, and it will run for about 3 -4 weeks. A full size Dometic will use ~1500 btu/hour,, Mine run ~1/2 time in the hot summer,, let in the winter. If memory serves,, a gallon of Propane contains ~79,000btu,, and a bbq tank holds ~5 gallons.

    Way cheaper to run than a dorm style fridge,, especially if it is only used on the weekends.

    Tony
  • rhine
    rhine Registered Users Posts: 10
    Re: New to solar, a few questions

    ok well it looks like i'm going to have to scrap the fridge but with the kit i mentioned at the begening do you all think that should be plenty to run the 5 lights?
  • Sparky
    Sparky Registered Users Posts: 23
    Re: New to solar, a few questions
    rhine wrote: »
    ok well it looks like i'm going to have to scrap the fridge but with the kit i mentioned at the begening do you all think that should be plenty to run the 5 lights?


    Don't feel bad, I'm new at this too.

    I just wan't to run a back up system for power outages. The cost is almost too much though.

    I want to run a Lcd TV, some lights and a fan or two.

    I've been selling some man toys around the house here, on Ebay. that way I can buy about half of what I'm thinking. not using the stuff anyway.

    Maybe just a 12 volt system a good size panel and good battery.


    It's a lot to get used to though.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: New to solar, a few questions
    I use a 45 watt kit to run two 12 volt, 120 LED bulbs out near my barn every night. It does well in the summer time, but needs a little boost from time to time in the winter. The 60 watt kit you mention would probably run 4 or 5 of these bulbs in the summer, but may struggle in winter with reduced sun time and cloudy weather. You can get this kit and bigger ones cheaper at my store, but this site isn't for advertizing. One thing I have found that works well is a 123 watt panel charging two 6 volt golf cart batteries wired in series. These things hold a good deal of power, and ran a big refridgerator all day without recharging during a recent power outage (I lent the batteries to a neighbor, along with my inverter). You can also purchase small DC refridgerators for tempory or emergency use and one of those may work fine for you purposes. Experiment a little, and you'll come up with a system you can be proud of.


    I would be very careful of any "small DC fridge" I have yet to see one that runs efficiently. That isn't to say there isn't one,,, but I've never seen one.

    Note to Semosolarstore,, As a piece of advice with regards to this forum. I have found over the years that it pays to be specific with our advice rather than too general. For example one of my "favorite" phrases is "do the math" Suggesting that a 123 watt panel will charge a pair of golf cart batteries. The charging capacity is pretty small (under 10 amps) for the batteries (~225ah) More importantly however is the generality such as "these things hold a lot of power". The reality to most newbies is that they (often grossly) over estimate the amount of solar they can get from X amount of panel, and they underestimate the amount their expected loads will really draw from a battery.

    Using your suggestion that a couple of golf cart batteries can run a fridge for a day is pretty misleading. Lets assume the batteries wired in series have a ah capacity of ~225. 225X12=2700 wh to 100 discharge. If you want the batteries to last more than one cycle you would want to only discharge to 50% max, and IMHO to ~70% ideally. That leaves between 810-1350 wh. A good energy star fridge will use ~ 750-1kw /day, an older fridge 4 times that much.

    Your 125 watt panel might put a maximum of ~ 250-300 watt hours into the batteries net useable out of the inverter. So if you were to use that set up you would be putting back into the battery less than half what you would be taking out each day.

    Finally people need to know that batteries "that need a little boost from time to time" need that boost in a very timely manner. Batteries (lead/acid) that are left at a state of charge of less than 80% will degrade very quickly and will never fully recover. Once you find that a battery is being over drawn/under charged it is too late. I suggest the following links:http://www.batteryfaq.org/
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    Welcome to the forum and good luck,

    Tony
  • System2
    System2 Posts: 6,290 admin
    Re: New to solar, a few questions
    rhine wrote: »
    Hi, I am trying to get power to a shed that cannot get power from the lines. What i would like to power would be 4 or 5 light bulbs and a small dorm style mini fridge. I found a starter system from northern and i was wondering if this one would do all of this. thanks in advance. http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200352703_200352703 also i plan on having 2 or 3 deep cycle batteries with at least 100 amp hours possible the D31m from optima http://www.optimabatteries.com/optima_products/bluetop/specs.php thanks in advance.

    Hi rhine,

    I am in a similar situation. I am new to solar panels and I am looking for help. I have done a little research and found a few good sites with information on solar panels and solar panel systems (Solar Panel Store and National Solar Panels). Both have good information. What system did you end up going with? Thanks in advance
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: New to solar, a few questions

    The "store" link was just another solar store--pricing and product (a quick check) was nothing special. NAWS had better pricing.

    The solar forum had only a couple posts--Why go there... This forum has quite a bit of activity?

    Dubbs, if you wish to participate here and ask/answer questions--please feel free. But directing traffic from a "free to everyone" board (sponsored/paid for by NAWS) to elsewhere is not appreciated.

    -Bill B. Moderator
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: New to solar, a few questions

    Dubbs,

    Welcome to the forum. There are some very smart folks here who have forgotten more about PV than most of us will ever know. I should caution you however, that the site is sponsored by Northern Arizona Wind and Sun, a very reputable retailer. They never interfere with our activity on this forum, but we try to show deference to them by not undully posting links to competitors web sites. That said, links to other products and services are proper.

    Good luck, read all you can, get yourself educated here by reading all you can, and you can avoid the biggest pitfall of RE/PV is the Ready, fire, aim syndrome.

    Tony

    Sorry Bill, you beat me to it! Point still stands.
  • System2
    System2 Posts: 6,290 admin
    Re: New to solar, a few questions

    Hi Guys,

    Sorry for anything I did wrong. I wasn't trying to send traffic to other websites I was just trying to be helpful. As you can see I am very new to this and I am just trying to read and learn on different websites. Again, I am sorry for anything that I did wrong.

    thanks