Different types of solar panels

momofgcm Solar Expert Posts: 35
I am a total newbie here but I understand the basic concepts of power and solar. It's the details that are killing me! This is a great board for info. It makes me want to go back to school for solar work.

We have 2 houses in Guinea, West Africa with off grid solar systems. The systems are older. We are curruntly trying to upgrade the systems but the stuff being ordered to upgrade the system concerns me. So, I'm trying to figure out what is really needed to make the system to make it better.

The goal was to get fridge/freezers for the 2 homes but I'm not convinced there is enough energy.

So, my first question is I see panels advertised as best for grid-tied systems and some better for off grid.

What is this difference that makes a panel better for off grid verses grid tied?



  • BB.
    BB. Super Moderators, Administrators Posts: 33,477 admin
    Re: Different types of solar panels

    For power measurement--If you can get a kill-a-watt meter (there is a UK version if you are using 230 VAC for your home wiring) is hard to beat. If you can get an old utility meter--you can also use those to log your power usage over time (may be easier to get in your area).

    In general, any good quality "Grid Tie" solar panel will work well for Off-Grid systems with an MPPT charge controller.

    In general, the Grid Tied panels are larger wattage (cheaper $$/Watt pricing) and higher voltage than those designed for battery banks.

    However, there is one major issue... The "high voltage" Grid Tied Panels (typically around Vmp=48 to 72 volts) are too low of Vmp to properly charge a 48 volt battery bank. And you cannot put 2 panels in series without Voc (Voltage open circuit, cold) creating too much voltage for MPPT charge controller.

    Otherwise, proper planing for Charge Controller + Solar panels before you buy them is always recommended.

    If you are using PWM solar charge controllers--It is much more difficult to find a "Grid Tied" solar panel that will cost effectively match your battery bank voltage...

    For example, a "12 volt" solar panel has Vmp~17.5 volts... If Vmp is much lower, a hot solar panel will not properly charge a battery bank. If Vmp is much higher, it will not charge a battery bank with as much energy as the panel is rated for (wasted/unusable watts from solar panel).

    If you have detailed questions, please feel free to give us the Panel Name/Model and/or specifications (how many panels/watts you plan on using)--And let us know what Solar Charge Controller(s) you are thinking of installing.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Different types of solar panels

    The rule of thumb I've seen, IIRC correctly, is about 1KW of PV needed for a good efficient fridge, off grid. Other household loads would still need more panels. So if you currently run fine with 400W of solar, and want to add a fridge, you'll need another 1,000 w of solar added, and a pure sine inverter to power the fridge from. I say pure sine, because:
    1) safe for the motor
    2) mod-sine, the motor consumes more power than nameplate, and you need 20% more PV to run it, if it does not burn up in a week.
    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 ,

  • russ
    russ Solar Expert Posts: 593 ✭✭
    Re: Different types of solar panels

    İ bought new electronic power meters - single phase for about 20 USD and the tri-phase for about 50 USD - class 1 meters.

    The single phase meter İ connect with plugs - works reasonably well considering İ haven't found anything like the kill a watt here.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Different types of solar panels

    actually even some of the other oddball voltage pvs that are lower in voltage than bb stated are also considered gt panels. generally, one can say that if it is not configured for battery charging suitable with a pwm controller with minimal loss in mind that it is for gt systems. for example a 24v vmp is too low for charging a 24v battery bank and will charge a 12v battery bank with allot of losses.
    the guys are right that you need to know how much power is being used by those appliances over a typical or even worst case 24hr or better period. this will give you the kwh consumption that one can use to help calculate the pv needs. the amount of full sun hours one gets as well as the time of the year is also possibly needed in this determination.
    you might want to give us more details on what you have and what it produces now for how much power to the appliances? what is on order? etc. etc.