Off Grid Camp-No experience w/solar

SystemSystem Posts: 2,511 admin
Looking to upgrade existing solar (15 watt panel ) which was there when i purchased the camp. It currently runs 4 dc lites and an rv waterpump which are used sparingly. Would like to run a satelite system, tv and 3 more lights. I haven't researched yet to find out the power requirements so i am just looking for general advice on batteries, panels and controllers.

The site location is not quite ideal with the area being occasionally and partially shaded or in direct sunlight at different times of the day.

So do i go w/mono panels vs pv panels ?
1 large panel or smaller multiple panels ?

Controller requirements ?

When charging with my gen. do i need a special battery charger?

Batteries ? I have a chance to buy used but not sure if i should or not, looks like a good beal but not sure if it's too much battery or not enough......16 used concord 12 volt 225 amp AGM batteries with Interconnects, sell in sets of 4 only,
$200 for 4, $800 for 16


I also plan to talk to professional dealers/ installers.

Sorry for being long winded for my first post.

Thanks Marty

Comments

  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off Grid Camp-No experience w/solar

    my responses in red.
    Looking to upgrade existing solar (15 watt panel ) which was there when i purchased the camp. It currently runs 4 dc lites and an rv waterpump which are used sparingly. Would like to run a satelite system, tv and 3 more lights. I haven't researched yet to find out the power requirements so i am just looking for general advice on batteries, panels and controllers.

    i seriously doubt that 15w pv is keeping all of those going without the battery dead or near dead most of the time. until you know what the kwh per day might look like you are swinging in the dark as to what you might possibly need in a pv system.

    The site location is not quite ideal with the area being occasionally and partially shaded or in direct sunlight at different times of the day.

    the sun is your power source and without it pvs are useless so the less sun the less power you get no matter how many pvs you buy. you may need a professional site evaluation.

    So do i go w/mono panels vs pv panels ?

    a mono panel is a type of pv panel. you can find many terms in the glossary in the upper section of the forum.

    1 large panel or smaller multiple panels ?

    it is usually desirable to go with larger pvs to a point. that point is when they would have difficulty carrying them and fitting them all in a given space. i do believe with all you plan to run you will most likely need multiple large pvs.

    Controller requirements ?

    that depends and you can cross this bridge when you have a better grip on other factors. you can read up on them and price them too just to get semi-familiar with them.

    When charging with my gen. do i need a special battery charger?

    it would be preferred that you have a charger that can do bulk (at least 5% rate), absorb, float, and eq with the eq not as necessary with agms. again look some up. keep in mind agms are not to exceed there max design voltage no matter what some el cheapo chargers may present with a one size voltage fits all.

    Batteries ? I have a chance to buy used but not sure if i should or not, looks like a good beal but not sure if it's too much battery or not enough......16 used concord 12 volt 225 amp AGM batteries with Interconnects, sell in sets of 4 only,
    $200 for 4, $800 for 16


    nice deals if they are any good. it's tough to determine their capacity without the equipment to do so with. with any battery you do not want to drain them beyond 50% so if you need as an example 100ah a day then the batteries should be at least 200ah and if you want a reserve then get more capacity, but keep in mind the more battery capacity the more it takes to properly charge them. we recommend at least a 5% rate of charge, but those agms can take far more than you'd ever have in pv capability.


    I also plan to talk to professional dealers/ installers.

    yes, do so.

    Sorry for being long winded for my first post.

    we don't care as some of us are longer winded. see bb's posts.:roll::p

    Thanks Marty
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Off Grid Camp-No experience w/solar

    Power wise--We can use a website like PV Watts to predict how much power a system will generate in average weather conditions... Picking Boston Mass, 1 kW (1,000 watts of panels--sorry, smallest program will accept), and for an off-grid battery system (no inverter--or most power used is 12 vdc), an overall derating of 0.22:
    "Station Identification"
    "City:","Boston"
    "State:","Massachusetts"
    "Lat (deg N):", 42.37
    "Long (deg W):", 71.03
    "Elev (m): ", 5
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.620"
    "AC Rating:"," 0.6 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 42.4"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","11.8 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.36, 67, 7.91
    2, 4.36, 78, 9.20
    3, 4.79, 92, 10.86
    4, 4.92, 89, 10.50
    5, 5.33, 95, 11.21
    6, 5.41, 90, 10.62
    7, 5.60, 96, 11.33
    8, 5.64, 97, 11.45
    9, 5.13, 88, 10.38
    10, 4.65, 85, 10.03
    11, 3.14, 58, 6.84
    12, 2.98, 57, 6.73
    "Year", 4.61, 991, 116.94

    57-97 kWHrs per month or 1/30 gives you around 2-3kWHours per day per 1,000 watts of solar panels... or ~2,000 to 3,000 Watt*Hours per day (depending on seasons). If you need 2x the power, then you would need 2x 1,000 watts of panels, etc...

    But, if you have lots of shading--any time there is not full sun on the panel, it will generate almost no power.... If you have clear sun ~9am-3pm, you will collect most of the sun. If you have 1/2 shading during the day, you will only collect 1/2 the power. And remember trees grow--so what may be acceptable now, may not be 5 years later...

    Shading is a killer--does not mater if large or a bunch of small panels. If you can put the panels 100+ feet in a different location--can you get more sun?

    There are two major classes of charge controllers... PWM (cheap, efficient, not very flexible) and MPPT (2x as expensive, can be very flexible with long panel wiring runs). But--don't focus yet on the controllers...

    We really need to know how much power you plan on using and how much sun/solar panel you can install given the site limitations.

    Deep Cycle batteries tend to need higher voltage chargers than regular automotive battery chargers output. Also, some chargers come with remote battery temperature sensors which help a battery charge quickly and fully.

    The charger you choose may be different if you only have generator or if you have grid/utility power. You need to size the charger both to your battery bank size and the size of the generator you will be using for charging.

    The size of your battery bank is also really based on your loads... If you get too small of battery bank, you may have to run your generator more often in bad weather... If you get too large of battery bank, you may need more solar panels and larger charger/generator to keep the bank properly charged...

    In the end, we really need your planned loads and then design the system...

    We can design a system around a battery bank, or solar panel array, etc... But you may end up not being happy because it does not meet your needs (or requires too much solar panel / generator / fuel to keep properly charged).

    If you are starting with a 15 watt panel--you have almost no solar power (maybe 30 Watt*Hours per day)--So that any 100-600 watt solar system will be a huge increase in energy.

    The problem is that satellite receivers/computers/TV's/pumps can take a lot of power... It is not necessarily their "peak watts" that is the problem--it is that they are running for many hours per day.

    Picking energy star/conserving appliances and electronics will make your solar power requirements smaller--which will save you money in the long run...

    A starting point for good / reliable equipment would be our host's webstore (NAWS)--You are welcome to purchase there or not--this is a public forum and we try to help everyone... None of us here (other than the Admin Windsun) is connected with the store in anyway (some people here have been their customers over the years).

    You really need to measure your power requirements... A Kill-a-Watt Meter is great for 120 VAC 15 amp plug in devices (and for use around your home for conservation). If you will have a lot of DC power needs--you can use a DC Amp*Hour / Watt*Hour meter like one of these.

    Solar RE system and component selection, to a large degree, is based on your power needs... Small systems use smaller/fewer/cheaper components. Large systems use larger/more expensive building blocks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Off Grid Camp-No experience w/solar

    Thanks for the responses.

    Am trying to detail my power requiremenrs now. One thing to consider s that the electronics will typically run up to two hours in the morning and then in the evening the same on a weekend with an occasional weeks vacation thrown in during July and August. Currently according to my meter the batteries ( 2 rv marine batteries 115amp hour ) run about 12.5 to 13.9 v when i am there.

    Marty
  • mike95490mike95490 Solar Expert Posts: 8,369 ✭✭✭✭✭
    Re: Off Grid Camp-No experience w/solar

    Just a wild guess, 200w of PV, well managed, could do it, but you will be pinching each watt to make it work. 400W of PV, you should be very comfortable.
    But it all depends on your loads.
    Too bad Morningstar does not have a 24V version of their suresine inverter, that would make it possible to use their 15A MPPT charger @24V w/400W of PV.
    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 ,

  • System2System2 Posts: 6,290 admin
    Re: Off Grid Camp-No experience w/solar (Updated)

    Okay here are my calculated power requirements.

    Satelite System according to the guys at radio shack....

    Sat. will draw 25w ? Sounds low but thats what the receiver had on it.

    lcd tv up to 120 to 150w depending on size i buy.

    4 dc lites @ 13w.

    rv water pump [email protected] minutes a day.


    Sat, tv and lites used 4hr a day on Fri, Sat and sunday with one weeks use during july and august.

    Not sure if i should but 4 of these supposedly immaculately cared for 10 year old batteries that load tested well from a dealer but if i do how many would be needed to supply my power needs

    (used concord 12 volt 225 amp AGM batteries with Interconnects, sell in sets of 4 only, $200 for 4, $800 for 16 ad tested well from a dealer)
    [/B]
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Off Grid Camp-No experience w/solar (Updated)

    my comments in bold black and in parenthesis. i hope i didn't goof in any of my math or thinking here.:roll:
    Okay here are my calculated power requirements.

    Satelite System according to the guys at radio shack....

    Sat. will draw 25w ? Sounds low but thats what the receiver had on it.

    (it may be less, but we must go by the rating unless otherwise known for sure. this will be 24/7 unless you switch it off. i'll list it as 6 hours as you may need it on a few extra hours for updates. 6 x 25w = 150wh)


    lcd tv up to 120 to 150w depending on size i buy.

    (by worst case 150w x 4 = 600wh.)

    4 dc lites @ 13w.

    (this can be up to double that wattage due to power factor. 4 x 2 x 13w = 104wh)

    rv water pump [email protected] minutes a day.

    (i hope you're right on this one, but i'll go by what you state. 75w x .5 = 37.5wh)

    Sat, tv and lites used 4hr a day on Fri, Sat and sunday with one weeks use during july and august.

    (i'll go strictly on a day basis giving a total of 891.5wh. dividing this by the number of hours of full sun gives the w needed to be delivered to the battery(s) every day. stc ratings aren't normally delivered by a pv every day and there are other losses and efficiency factors so you may need up to 50% more in stc rated pv to make it work. as an example with 4hrs full sun/day this would equate to 223w x 1.5 = 335w and possibly more if the pvs are not aimed well enough.)

    Not sure if i should but 4 of these supposedly immaculately cared for 10 year old batteries that load tested well from a dealer but if i do how many would be needed to supply my power needs

    (used concord 12 volt 225 amp AGM batteries with Interconnects, sell in sets of 4 only, $200 for 4, $800 for 16 ad tested well from a dealer)

    (for 10yr old batteries that could be a high risk even though they test good now as they are apt to go any time. i'd make him an offer at less than half of that, but that'll be your call as to what to offer for they could be scrap in less than a month or several years as it is unknown how much longer life they may have. 10yrs is pushing it for nearly any battery.
    as to how much battery you may need 891.5wh/17.6v vmp = 50.65ah. a minimum of double that so as to not go below 50% dod means 101.7ah. to add a day of backup would double that to 203.4ah which 1 battery would suffice for. if you go with more batteries remember that it takes more charging current to properly charge them. with 335w of stc pv this could maximally be 335w/17.6v vmp = 19a or 8.46% for 1 225ah battery, but we aren't taking into account the losses as 223w we figured on reaching the battery(s) after all losses and efficiencies so 223w/17.6v vmp = 12.67a or a 5.6% rate for 1 225ah battery. both cases are within the recommended 5-13% normally recommended range. more than 1 battery would necessitate more power in pv to charge it.)


    [/B]
  • icarusicarus Solar Expert Posts: 5,225 ✭✭✭✭
    Re: Off Grid Camp-No experience w/solar

    Marty,

    A couple of thoughts,

    As for loading,

    Sat box 25w *4= 100 wh
    TV 150*4= 600 wh
    4 bulbs 13*4*4=208 wh
    Pump 75*.5=37.5 wh

    Total 946,, let just call it 1kwh.

    Several rules apply to small off grid systems. The first is that folks almost always under estimate their loading. Second, they almost always over estimate their average solar potential, and finally, in spite of the best of intentions, loads always grow with time.

    If I were you, I would look at a base load of ~1.5-2kwh day.

    To get that much PV here would be my quick calc.

    Battery based systems have a net/net efficiency of ~55%. I like to use 50% just to keep the math easier. That covers all the built in efficiency loses that you can't (for the most part) eliminate. PV ef, charge controller ef, basic battery charging ef, inverter ef, various line loses et.

    So what I do, is take the name plate rating of a PV system, divide it in half, then multiply that number by 4, (to represent the number of hours of good sun one might expect) One seldom sees more than four hours of good sun on average over the course of the year.

    So, 500 watts of PV might look sort of like this:

    500/2*4=1000 watt/hours.

    You can play with the numbers anyway you wish, but the reality is usually pretty close. Just for example, we live with ~400 watts of PV, and we use ~6-800wh/day. This is with no TV, two lap tops, sat internet, multiple lights, water pumping, telephone, radio, fans etc. We use LP for fridge, heating, water heat. We make coffee on the stove with a coleman MR Coffee system, and we make toast using a catalytic propane heater! (We do have a heated mattress pad though! whoo-hoo!)

    With that 400 watts of PV we harvest ~800wh-1kwh on an average day. A perfect, cold winter day with lots of reflection and no clouds, we have harvested over 2kwh. To day for example was a fairly average late winter day, a mix of sun and cloud, and we harvested just about 800 wh.

    So, figure your loads, realize they will grow, and plan accordingly.

    Tony
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