Solar Source and Stabilisation

Discussion in 'The Projects Forum' started by chal-lo, Oct 4, 2012.

  1. chal-lo

    Thread Starter New Member

    Sep 10, 2012
    6
    0
    Hi there,

    I am an electronics hobbyst and am trying to build a stable source of current from a series of solarcells in order to feed a secondary battery which would hold the stable voltage source in the end.

    this battery would be responsible for feeding the energy supply to the circuit that the solar cell is not able to deliver during night hours.

    The power source must be at least 9v high. But as far as I have seen series connected solar cells would attaint that pretty easily. The point is to conserve that energy once it has been supplied to the battery.

    I am not familiar at all with such batteries, I presume they must be rechargeable batteries, so in a way and forgive my ignorance, sort of huge capacitors. And due to the instability of the power source, a diode would have to be placed in between in order not to supply back to the solar cell the energy, because of a superior voltage decrease in the solar cell with respect to the capacitor/battery.

    So in the end I would have a set of series connected solar cells in order to add-up a given voltage source, then a diode connected in series (or rectificator bridge, but the solar source is not of AC nature is it???, it's basically unstable), and finally also after the diode in series connected the battery/capacitor. After that I would have the load for the circuit connected to the battery/capacitor.

    This is a very introductory first attain for accomplishing this. I am still not focusing on how to enable/disable the circuit on a given current level for the battery/capacitor. For the time being I only want to accomplish that this battery/capacitor is able to store that energy in order to stabilise the current in my circuit.

    Don't know if there are any AC circuits dependent on solar energy, but as you may presume, this is a full DC circuit.

    In order to help understand I provide a quick draft of what I mean (drawn by hand : sorry!!!!). In the draft I have included the possibility to include a power dependent source, but that's a mistake so please omit that.

    Any thoughts are greatly welcome.

    Many thanks in advance for your help.

    Chal-lo.
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    Such a system is very possible. I frequently buy small systems such as this to run my garden lights for a few dollars. They may generate a few hundred milliwatts. I also work on a system to power the house load on a lighthouse where the panels are rated 150 watts total.

    Successful systems balance the power needed by the load to the energy the solar cells can provide against the storage capacity of the battery (or cap).

    These systems are pure DC, no need for a bridge rectifier. A single diode will do, it's purpose is to keep the battery/cap from discharging into the panel when it's dark.

    Fixed your schematic sketch:

    [​IMG]


    However, without any idea of your load no further comments are possible.
     
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  3. MrChips

    Moderator

    Oct 2, 2009
    12,418
    3,355
    What you are suggesting is a simple way to charge the battery from a solar panel.

    Solar power systems are fairly mature and readily available off the shelf. But that doesn't mean that you cannot roll your own or come up with fresh ideas.

    Basically, one would use a step up DC-to-DC converter to allow harvesting the solar energy even when the clouds roll in.

    For energy storage, lead acid batteries are the most cost effective in terms of power density/recharge cycles/cost etc.

    The next part is getting the energy to the load. For this, conventional systems use a DC-to-AC inverter in order to feed the power into the grid system. People do this because currently you get more money selling the power back to the grid than using it yourself.

    If you can drive your loads directly with the DC voltage from your batteries, for example, powering LED lighting or electronics, then your energy transfer would be more efficient.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    +1
    Don't overlook this point. Many visitors here have unrealistic expectations for their solar project; they expect more power than the panel really delivers (expecting full voltage at the peak, short circuit current), don't allow for charging/discharging losses (about 50%), and don't think about the effects of clouds and all the other things that cause less-than-full sun on the panel.
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    First start with the average 24 h load required. Battery bank should at a minimum. supply 24 h without recharging. Questionable math but here goes: Assuming a 1/4 W load = to 7 AA NiCd's @ 700 mAh. To supply load & recharge about 1500 mAh for 10h @ 50% effectiveness = 300 mA. For 9V battery need minimum 15 V OC panel giving about a 4W panel. A panel for trickle charging car battery is about 2W, 130mA SC & 20 V OC. Measures 12 in X 6 in, having 30 cells.
     
  6. chal-lo

    Thread Starter New Member

    Sep 10, 2012
    6
    0
    That's right Ernie, the cap must go parallel to the load. Basic capacitor techniques.

    To all of you many thanks for your comments. Have already some guidance now.

    Chal-lo
     
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