Newbie DIY solar

Discussion in 'The Projects Forum' started by furby, Dec 30, 2012.

  1. furby

    Thread Starter New Member

    Dec 30, 2012
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    Im am new at this!
    I am wanting to build a solar setup that i can charge mainly mobile electronics with (non USB specific devices) all the way up to a desk top computer. I am looking to use a deep cycle gel/no maintenance type battery and because of space constraints no more then 2 batteries if at all possible. Also because I am renting I CANNOT run outlets. My thought was an extension cord. Is that even possible? ANY help in what type of panel and equipment to get and even if there are existing kits for my needs is greatly apprecated. One last crazy question. Is it possible to run a home heater off a solar setup or does any typical heater draw too much?

    Thanks
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    First thing to do is specify your max load. Then we can tell wht u shud get
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    If you are looking to charge some devices why the two large batteries? Just charge directly off the solar panels during the daytime.

    I doubt any sort of electric heater would give you any useful output. You may do better with a black plastic barrel you leave in the sun and bring inside at night.

    To design any solar system you need to start with your expected and maximum daily load. Then you can balance in what battery you need to supply that energy and what size panel to recharge it.
     
  4. furby

    Thread Starter New Member

    Dec 30, 2012
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    How might I go about defining what my max load would be? The reason I wanted the batteries was because i am typically at work before the sun is out enough to really get anything from it and am home shortly before night fall.

    The heater idea was a stretch. But I will take into consideration the black barrel idea. lol
     
    Last edited: Dec 30, 2012
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Heater is OFF, cause it will drain the battery just like tht.

    Your work environment is crucial if you have plans to use maintenance battery.
    Problem is that they give of gas during charging. You would need a sealed box with exhaust port to out side if the battery is in the room.
    That is why you should go for maintenance free types.

    I asked for a MAX load of your computer. The type of LCD or CRT should be taken into account and the max power rating of your CPU.

    The running time of your work at the computer is also crucial to decide the AH of your battery.

    Next is the inverter efficiency.

    After taking all these into account we can even guess a battery capacity.
    After that then comes the solar panel capacity.
    Last but not least will be how long the sunshine's at your area and all tht decides the power rating of the panel...!!

    PS. Not so easy than you thought ! HUH ! :D
     
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  6. ErnieM

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    Apr 24, 2011
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    My wife once bought us a "solar pool heater" that was just some black plastic tubing that got put into the filter line. It actually worked, but since it becomes a passive chiller at night unless you bypass it it wasn't very practacle: not like I would remember to turn a valve twice a day.

    To determine your load you need to take all your devices and add up how much power each needs. Yep, that can be hard to do but you need to have some sort of target.

    You can start by the battery capacity in amp hours for each, and factor in how discharged it will be, and how efficient the charge will be. I would guess the mobile things will be easy to cover but a desktop (and monitor?) will take a lot of capacity in batteries and panels too.

    I would advise not to build the system, but look at things like camping solar systems or other complete packages. That will give you a price target if nothing else.
     
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  7. furby

    Thread Starter New Member

    Dec 30, 2012
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    The working time for the computer would be 3 hours ideally. In my recent research i came up with some unfortunate new facts. These new facts bring rise to new questions.

    The first is that i realized that i will only get up to 5 hours of direct sun light in the summer and approx 3 hours in winter.

    The second problem is (if I am not mistaken) to find out the max power usage for my computer is to take the volts (i went on the higher end of the spectrum) times the amps and i get the watt usage per hour. This information was from the "input" on the power supply. Being that I am in a country that is running 220V would that not more then double my watt hour requirements from a battery because the input watt requirement does not change regardless if i plug the dual voltage device into 110 or 220. Or so says the info panel on the power supply.

    Example... a computer screen running on 110-120V at 1.2A will be 132-144 watts. The same screen running on 210-220V system at the same 1.2A will be a requirement from the batteries of 252-264 watts.

    IF my little research is correct with a worse case scenario my MAX (everything being used at once at its highest electrical usage) load is something around 1000 watts per hour and that doesnt seem possible to sustain from a small battery bank.

    Unless I have this ALL WRONG which is totally possible Or would it be better to go with a 110 only inverter to maximize the battery life?

    The camping solar systems are decently priced but I am interested if it is more cost efficient being I luckily live just a few miles from a solar panel producing company.

    The inverter efficiency would be 1200W to 1500W hopefully. Is that a decent range for me? My thinking is that it would give me roughly 200 to 500W leeway to power what i need and a little more at the same time if need be.

    Am I on the right track yet to doing this or are my ideas a little too ambitious for my wallet?
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Fortunately, I think you do have it wrong. A computer or monitor will use the same power (give or take) regardless of the source voltage. So they won't really use more on 220V than on 110V.

    You might want to get yourself a Kill-A-Watt device to measure how much power you're actually using. It will vary a lot with screen brightness settings, CPU and hard drive usage, and so on. So use the meter over a few evenings of normal use and you'll get a much better idea of what you really need.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Passive solar heating is far more sensible than making electricity first, only to waste it making heat. PV panels are only about 10% efficient at capturing solar energy, and battery charging is about 50% efficient. So end-to-end efficiency of making heat from PV panels is only about 5%. A black barrel is probably ten times better.
     
  10. mjsummers

    New Member

    Jan 2, 2013
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    keep in mind that the size of the power supply in the computer will determine the load for the computer (i.e. a 1100W psu will draw between 110-120Vac at ~1.5A) so you will need to include that into your solar power system. I ran into a problem while doing a similar project for school. The difference between this project and the one that i was working on is the scale and the size of the battery back, plus i included an automated switch that would completely remove the system from the local power grid and make it in isolated system.

    I was trying to provide solar/battery power to a house that was located in the mountains and the system was an emergency power source in addition to being standalone only.
     
  11. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    furby: I have no idea from the numbers you wrote how much power your devices draw. I get this is something new for you, so can you just type exactly what is on the devices (bricks, display, whatever) and let us interpret these for you.

    Power is power, 100 watts from 12V is the same as 100 watts from 120 volts or 220 volts, though each of these sources will need to deliver less and less current to achieve that same power.
     
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