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How To design An Off-Grid Solar Power System

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  • How To design An Off-Grid Solar Power System

    I want to first appreciate the Admin for activating my account to be be able to post on this platform. I am a student of Solar power installation and my search for more knowledge got me to this forum. I quite appreciate everyone here, thank you all.

    Now to the point, I need to design a solar system to power a load of 6000 watts for 5 hours daily, I believe I can get an average of 6 hours of sunshine in my country. I want the system to be able to power the load during the day off the sun and then at least for 5 hours at night time. How many panels, type of MPPT controller and batteries would be required? Thanks

  • #2
    Originally posted by Ifet View Post
    I want to first appreciate the Admin for activating my account to be be able to post on this platform. I am a student of Solar power installation and my search for more knowledge got me to this forum. I quite appreciate everyone here, thank you all.

    Now to the point, I need to design a solar system to power a load of 6000 watts for 5 hours daily, I believe I can get an average of 6 hours of sunshine in my country. I want the system to be able to power the load during the day off the sun and then at least for 5 hours at night time. How many panels, type of MPPT controller and batteries would be required? Thanks
    Assuming you mean "hours of sunshine" per day, what do you mean by "6 hours of sunshine" ?

    Each hour of sunlight will have a different energy intensity (radiant flux) and, depending on angle of incidence on a PV device, a different amount of energy hitting that device. A more useful number in the sense it's less prone to misinterpretation is the energy (in units of kWh/m^2) a PV device sees per day in the plane of the device averaged over some time period such as a week or a month or a season. For example, my array, on average, over a "typical" year, has ~ 5.81 kWh/m^2 per day of incident solar radiation in the plane of the array (P.O.A., irradiance). If the array were horizontal it would see ~ 5.27 kWh/m^2 per day of incident solar radiation. If some other orientation, the P.O.A insolation would be a different number again. Some would call that P.O.A. irradiance of 5.81 kWh/m^2 per day for my array orientation "sun-hours" per day. Some others would call it 5.27 "sun-hours" per day. If some other array orientation, that P.O.A. number would be still different. Yet, on average, the sun casts a shadow around here about 70 % or the time or about, on average, 8.4 hours per day over any consecutive 365 day period. Which is it ? See why the term "sun-hours" can cause confusion, especially among those new to the field ?

    Sometimes (and unfortunately IMO) that number (kWh/m^2 per day) is called "sun-hours" with a common result being that the uninitiated get confused by the possible likely assumption or inference that all sunny conditions and device orientations produce or have equal solar potential so that, for example, more than a few folks think a day with 12 hours of daylight has 12 "sun-hours". or, if the sun "shines" - that is, casts a shadow - for 6 hours per day, that day has 6 sun-hours. Using radiant flux per time period in the plane of the device (kWh/m^2 in the plane of the array) per time period causes less confusion and less opportunity for fewer mistakes that can happen and about equally importantly, don't need to be made. It might take a liitle longer to write and a minute or two of brain exercise ot learn something, but I bet the effort is worth more than the confusion and mistakes it avoids.

    So far it looks as though you may you've identified the load. You next need to define the solar resource availability in terms of kWh/m^2 per day in the plane of the array(s), and how that availability varies over the course of a year, with the size of that period varying from probably a day (if this is an off grid application) to some f(energy storage size) and/or other criteria.

    How deep is your has been your foray into alternate energy at this point in your education ? That is, what do you know of the scope of your task, the availability of the solar resource and its general temporal distribution pattern for the site and what do you know of what types of solar powered equipment is available to possibly perform and fulfill some or all of that task ?

    Take what you want of the above. Scrap the rest.

    Welcome to the neighborhood.

    Comment


    • #3
      So, are you saying you have

      Loads
      6,000 watts 5 hours day time
      6,000 watts 5 hours night time time


      That's going to require about 15,000 watts of PV panels to perform both powering the 6kw load, and recharging batteries.

      6kw x 5 hours nighttime = 30kw of use off of batteries at night. That means close to 50kwh total storage needed.

      This is a VERY BIG project.
      Powerfab top of pole PV mount (2) | 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

      Comment


      • #4
        Originally posted by Ifet View Post
        Now to the point, I need to design a solar system to power a load of 6000 watts for 5 hours daily, I believe I can get an average of 6 hours of sunshine in my country. I want the system to be able to power the load during the day off the sun and then at least for 5 hours at night time. How many panels, type of MPPT controller and batteries would be required? Thanks
        VERY roughly:

        You will need 30kwhr worth of storage - which means about 40kwhr of good batteries (LiFe or similar) or 60kwhr of lead acids. For lead acids (cheaper) that would be 24 count of SIND 02 1990 or equivalent - which would be roughly $15K. That is for ONE day of storage. Three days is much wiser (weather and all that) so that's $45K for 240kwhr worth of batteries.

        To maintain a battery that size you will need at least (C/13) = 18kw of charging. Assume a 75% STC to real factor and you are at a 24kw array. In quantity you should be able to hit 50 cents/watt so that's $12,000 for the array.

        Now you have to see if you will get enough power to meet your load needs. 18kw will give you about 100kwhr in a good location (Phoenix) and 54kwhr in a bad location (Maine.) So you are likely OK there on _average._ However it's likely you will need a generator in the winter.

        For charge controllers, you'll need a few. Classic 150's will do about 100 amps and you'll need four of them. Another $1000 ea.

        Inverters you can use a Radian for simplicity. $4000.

        So that's (45+12+4+4)=$66K. So your basic components will run you about $66K. Add another 30% or so for BOS components (racking, protection, wire, conduit, battery shed) and you are at about $90K. If you are going to get someone to install it (which would be a VERY VERY good idea) I'd expect it to hit about $150K.

        Does that sound good, or does it make you run away screaming?

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