Question about solar power in green house.

kienewkienew Registered Users Posts: 3
edited March 2016 in Construction #1
Hi all, just joined now. I'll describe my situation first. I have a 50w solar panel, my plan is to put it on my greenhouse to power my irrigation system, running into a 20a 12volt to 240v solar charge controller, then to one batter and an inverter to power a small 12v pump on a timer. But I also have a peltier module kicking about somewhere. So this is my question.... Can I wire the module into my solar charge controller? I'm really new and a novice this idea with the solar panel only started 2 days ago when I was given a solar panel. And the peltier module I got a few months ago for my daughters project. Thanks Kieran. 

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Welcome to the forum,

    You are very confused. 
    kienew said:
    running into a 20a 12volt to 240v solar charge controller
    This makes no sense.  The solar controller takes the output of the solar panel (probably about 18 volts) and sends it to the battery.  I've never heard of a controller that could take 12 volts from a panel and make 240 volts to charge a battery. 
    kienew said:
     then to one battery and an inverter to power a small 12v pump on a timer.
    An inverter takes the 12 volt DC battery output and converts it to 120 volts AC.  If you have a 12 volt DC pump, you don't need an inverter... it can run directly off the battery.
    kienew said:
    I also have a peltier module kicking about somewhere. So this is my question.... Can I wire the module into my solar charge controller?
    What do you think you will accomplish by connecting a Peltier device to a charge controller?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • kienewkienew Registered Users Posts: 3
    edited March 2016 #3
    Hi ignore the 12 volt part I was a little confused there. I wanted to use an inverter so I could plug maybe a radio or any other appliance in when in the greenhouse. And the peltier module part was just out of curiosity as it puts out voltage so I was thinking it could be connected to a solar controller to charge a battery without over doing it if I forget it's connected for say a week. This is all really really new to me but I find it really interesting please don't take my ignorance as insult. Thanks.
  • BB.BB. Super Moderators Posts: 26,768 admin
    edited March 2016 #4
    Most people way over estimate how much power a solar system can supply and underestimate how much power they will use.

    Also--To keep things easier to follow--Ask one set of questions on a specific project first (such as water pumping) and then ask about unrelated project (say Peltier module) second.

    A 50 Watt solar panel in London England will (on average) see this amount of sun:

    http://solarelectricityhandbook.com/solar-irradiance.html

    London
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 38° angle:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    1.27
     
    2.04
     
    2.76
     
    3.67
     
    4.17
     
    4.20
     
    Jul Aug Sep Oct Nov Dec
    4.25
     
    4.16
     
    3.26
     
    2.41
     
    1.53
     
    1.05
     
    Say you start planting in March--That is (on average) 2.76 Hours of sun per day:
    • 50 Watts * 0.61 DC system eff * 2.76 Hours = 84 WH per day (March)
    Or, if you work in Amps and Amp*Hours:
    • 84 WH / 12 volts = 7 AH @ 12 volts
    A typical 12 VDC Water pump (used in RVs for sink/shower):

    http://www.solar-electric.com/wind-and-water-products/sodcwapu/shacdcwapu/sh80sedepuan/8000-443-136.html

    Will use between 4-7 amps (roughly) depending on pressure and flow:
    • 7 AH / 4 amps = 1.75 Hours of use (average March day)
    A 12 volt battery that would supply 2 days of stored energy and 50% maximum discharge would be:
    • 7 AH per day * 2 days use * 1/0.50 maximum discharge (for longer battery life) = ~28 AH @ 12 volt battery
    While you can run an AC inverter from such a small system--It really is not very practical. Most AC loads would be too large to run a "useful" amount of time on such a small system.

    Does this help?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kienewkienew Registered Users Posts: 3
    Yes this helps loads. The pump will be on a timer coming on 3 times a day for 1 minute at a time. I'm always messing about with stuff and it drives  our lass mad. Plus it's homebrew time so that's another thing to cheese her off. Thanks again. 
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