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Solar again... but bigger

Discussion in 'Renewable Energy' started by Misterbenn, Jun 19, 2007.

  1. Misterbenn

    Misterbenn Active Member

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    Location:
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    So i've just managed to get hold of two 160W solar panels...although in england i dont think they'll be able to create full power.
    Its not really enough energy to link to the mains and also you dont get paid all that much to feed back to the supply. so i want to use all the energy on site.

    saddly although energy is a preium during the day at peek times i'm generaly not home and thus there is very littel energy usage.
    I plan to charge up a set of heavy duty batteries,

    This is problem one...a very un-reliable supply so i need to create an efficient charging method.

    then i need to use the power...i'm not sure what on though...
    i have a few night lights that come on every night but there both energy saving so wont create much of a drain anyway, really i want to use most of the energy i've created in one day.

    Also does anyone know...if my batters are fully charge thus not charging and no load is thus conected to the solar panles will this damage them?

    any other suggestions on what i can use the power for?? All sugestions welcome.
     
  2. bryan1

    bryan1 Well-Known Member

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    Hiya Misterbenn,
    Those sound like good pv panels but thats only the first part of it. You need a good charge regulator and some deep cycle batteries and an inverter to power things. You dont say where those panels are 12 volt or 24 volt but all my solar arrays are 24 volt and I tend to stay away from 12 volt due to the extra current draw at hte lower voltage, also 24 volt inverters tend to be better built. Stay away from modiefied sine inverters and I bought a 3kw pure sinewave from kipoint in taiwan. It power most of my engineering tools no problem and seems good quality. They do sell them on ebay but go direct to their website and buy direct as I did. Ok for the charge controller connect your panels up in full sun and check the open circuit voltage, then put a battery inline and check the current. This will determine what size charge controller you need. If you like I can give you a charge/dump controller circuit you can male yourself. It works when a preset voltage is detected the dumpload is engage by triggering a mosfet and a simple rc network determines the delay before checking the voltage again. I've made 2 of them and use them on 2 of my smaller arrays.

    If you need anymore helps just singout mate;)

    Cheers Bryan :D
     
  3. Misterbenn

    Misterbenn Active Member

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    there two diferent panles, one is 28V and the other is 30V at peek. so clearly these cant just be conected in parallel due to circulating currents.
    becuase i need to do it on the cheep i was thinking normal car lead-acid batteries - maybe recycle some (tho i'd need to c if i can do that!).

    I dont know much about the charging of batteries, i'm currently looking at charging methods...constant current then constant voltage seem to be fairly common. In relation to voltage does the battery voltage need to be similar to that of the solar supply? i know this will affect the current but are there any other considerations?

    Also as the two diferent solar panles are slightly diferent voltages i suppose they'll both need a seperate charging circuit...unless i conect them in parallel and then use a DC-DC converter to bring it down to charging voltage.

    As for the inverter i got one from maplins a few years ago, just a 150W one, i wouldnt think its very efficient, but i imagin it'll do for now.
     
  4. dave

    Dave New Member

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  5. Misterbenn

    Misterbenn Active Member

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    Bryan,

    I just saw your other thred, and the solar panle next to your water tank looks to be the same as one of mine :)
    so it would apear your help would be invaluble! I have to find some good battries for a relativly cheep rate, and i may also need a new inverter i guess!
     
  6. bryan1

    bryan1 Well-Known Member

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    hiya misterbenn,
    Those panels you have are 24 volt nominal and I wouldn't worry about the 2 volt difference. So by putting them in parrallel will be the go. DONT use car batteries as they wont last long at all what you need is deep cycle batteries with a reasonable A/H(amp/hour) rating.

    I.E.
    1. My house batterybank is 12-2 volt 600A/H sonnenschein batteries hooked up in series to provide 24 volts

    2. My shed battery arrays are 28-6 volt 110A/H hooked up in series/parrallel to provide 24 volts and 24-2 volt 275 A/H hooked up in 2 arrays of 12 batteries to provide 24 volts.

    I wont bother mentioning my other arrays as they are different voltages.

    That 150 watt inverter is only a toy so go for something atleast 2kw sinewave with a 5kw surge minimum.

    My house inverter is a selectronic 24 volt 2.4kw with a 7kw surge pure sinewave and the main shed inverter is a kipoint 3kw with a 9kw surge pure sinewave.

    I'll find the link to the charge/dump controller in the next few days for you but I have to ask my mate who designed it if I can put it on this forum.

    As you can see from what I have mentioned above you need a decent deep cycle battery bank to provide any reasonable amount of RE power and although your panels will provide some charging power I'd suggest a home made wind generator to help charge the batteries. Checkout the sticky in ths forum and the backshed link is a forum and website where you can use a fisher&paykel washing machine motor and convert it into a wind generator.

    Just make sure you do a heap of research first and dont just dive in on the first aparant bargin. RE power can be affordable if you can find good secondhand batteries cheap and your part of the way there with those solar panels.

    Cheers Bryan :D
     
  7. silvarblade

    silvarblade Member

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    i have planned to buy some powerful arrays and use em to charge a ups . that would good huh? power outages do occur here and we have a hell lot of sun here too. by the way is there any way one can use heat you know convert it to some useful form.? :rolleyes:
     
  8. Thunderchild

    Thunderchild New Member

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    hot water steam turbines ?
     
  9. Misterbenn

    Misterbenn Active Member

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    Thanks bryan.

    I'm looking into batteries currently, were did you get your 24v array from. i may have a slight problem with finance for batteries...i so far have a limit on this system of £250 not much to buy all my equipment.

    I do have a contact to get an inverter, which i may be able to use.

    I've looked up chargers a bit, i'm planing to use lead acid batteries with a maxim two stage charger (fixed current / fixed voltage), and i'm thinking about adding undervoltage disconect. However the Maxim charge voltage is limited to less than 19V.
     
  10. Super_voip

    Super_voip New Member

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    silvarblade, to convert heat into "useful" energy try pielter devices or stirling engines. Having looked at both I'm going with Stirling engines 50% efficient rather than 2-3%
     
  11. Oznog

    Oznog Active Member

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    You can easily look up what % of the standardized rating will make in England. It's significantly lower.

    It does not hurt a solar panel to leave it in the sun without loading it. Nor can a panel be damaged by over loading.

    You may complain about not getting back all that you put in when selling power back to the plant, but consider this:
    1. Lead acid cycle efficiency varies, but 70%-80% isn't too far off. Energy is lost.
    2. Lead acid storage capacity is quite expensive, and has a limited lifespan as far as both calendar life and number of charge cycles even if ideal battery treatment is used. Cheap batteries often don't last long enough to even justify the initial savings.
    3. Once your battery is fully charged, unless you can use it or have the equipment to sell it back to the grid then the capacity is just wasted.
     

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