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Thread: Solar backup power

  1. #1
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    Default Solar backup power

    Does anyone have any experience with these? I know many have deisel or other fuel-powered backups, but I haven't seen much about solar.

    I don't have the ability to store up large amounts of fuel for a generator and quite honestly, living in the suburbs I don't know that I want to attract that kind of attention to myself with any fuel barrels or the noise from the generator.

    I've seen some stuff by Sunforce that looks kind of interesting but I don't know anything about them.

    Comments? Advice?
    The difference between stupidity and ignorance is that ignorance is a choice.

  2. #2
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    I've been dabbling in a bit, very expensive, especially depending how much energy you want to generate. Then again, expensive is relative in many ways and to different people depending on their income. Not economic in the sense of trying to lower your electric bill. The solar will allow for some small things to run and make an extreme SHTF scenario more bearable

  3. #3
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    I found a Sunforce one just surfing around Amazon.com. About $900 but the reviews say the power converters and other hardware aren't the best. One review said to just buy the solar panel add-ons then purchase different converters, etc. I've seen the advertisements to mysolarpower.com but from doing a little research it sounds like those are junk.

    Plus I know I'd have to get some marine batteries to charge. I don't know what, if any other hardware I'd have to get to set that up. But I bet it would cost, total, of around $2,000 for a 'decently' set up system. Not anything you're going to run the household on, but at least able to supply power to something like, fridge n freezer, maybe some heat if necessary.
    The difference between stupidity and ignorance is that ignorance is a choice.

  4. #4
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    Just talked to a freind today on a visit about this very topic. The absolute first think to do is figure out what all you want to be able to power and add up the total wattage. This is the number you need to base your system on. I would also allow for 10-20% extra to make up for losses due to line loss of the length of your wiring run and ineffeceintes of your system. My buddy showed me a months worth of testing he performed with one of his panels. I was surprised how little it provided. He took cloud cover, snow cover, and other things into account and did a hour by hour comparison. On cloudy or partly cloudy days there was hours that he got little to nothing out of the panel. Tracking the sun is also a important factor. I would be surprised if you couldn't increase your output by 30% or more by doing this.
    I'm looking into this for a couple of smaller uses and will be doing research on this myself. One item to check out is called "Kill A Watt". It plugs between the electric outlet and whatever your are powering. It measures many different things over a period of time that will provide information you need to build your system. Also check out "Home Power" magazine, which also is available on line. They discuss all alternative energy options and have ad with web links for many different solar providers.
    Greater love hath no man than this, That a man lay down his life for a friend.
    John 15:13

  5. #5
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    I can not stress enough that you will save a fortune by building your own panels rather than purchasing a premade one.

    Right now, you can buy a box containing 36 tabbed 3"x6" solar cells, rated at 1.8 watts each. When coupled together and placed in a homemade frame, you should have a fully functioning 60 watt / 18 volt panel.
    Total cost: $70 for the cells, maybe $10-$20 for the frame material.

    Whereas a premade 60 watt solar panel is going to run you about $250-450 depending on who you buy it from.

    Then you need a power inverter and a battery bank.

    The cost of an inverter should be entirely based on the total output of power you are producing. For example, you can pick up a 1000-watt inverter for about $100. Or even a 400-watt inverter for about $50. Now a 1000-watt inverter will be able to convert all of the power you could get from about 16 60-watt solar panels. A 400-watt inverter can handle about 6 solar panels. It all depends on what you really need.

    So lets say you are going relatively cheap and only want about a 400-watt backup system. You will need:
    - (1) 400-watt inverter
    - (6) solar panels
    - (6) deep cycle 12-volt batteries

    At $50 for the inverter, about $80 per homemade panel, and around $70-100 for the batteries, you are looking at a grand total of $950 - $1130 for a homemade system.

    400-Watts for about $1000. However, you can make the system as powerful as you need. It will cost you, but will cost you exponentially less than these prefab kits. It just takes a little bit of work.

  6. #6
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    Thanks BP. Thats a great place to start.

    One thing I'd like to find out as well is how many batteries would be, at least minimally required to hold a charge. At the very least to power a freezer during cloudy days or night. But at least for some emergency power if I needed elsewhere.
    The difference between stupidity and ignorance is that ignorance is a choice.

  7. #7
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    Thanks for the info Allen. Much appreciated!
    The difference between stupidity and ignorance is that ignorance is a choice.

  8. #8
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    Quote Originally Posted by allen_idaho View Post
    I can not stress enough that you will save a fortune by building your own panels rather than purchasing a premade one.

    Right now, you can buy a box containing 36 tabbed 3"x6" solar cells, rated at 1.8 watts each. When coupled together and placed in a homemade frame, you should have a fully functioning 60 watt / 18 volt panel.
    Total cost: $70 for the cells, maybe $10-$20 for the frame material.

    Whereas a premade 60 watt solar panel is going to run you about $250-450 depending on who you buy it from.

    Then you need a power inverter and a battery bank.

    The cost of an inverter should be entirely based on the total output of power you are producing. For example, you can pick up a 1000-watt inverter for about $100. Or even a 400-watt inverter for about $50. Now a 1000-watt inverter will be able to convert all of the power you could get from about 16 60-watt solar panels. A 400-watt inverter can handle about 6 solar panels. It all depends on what you really need.

    So lets say you are going relatively cheap and only want about a 400-watt backup system. You will need:
    - (1) 400-watt inverter
    - (6) solar panels
    - (6) deep cycle 12-volt batteries

    At $50 for the inverter, about $80 per homemade panel, and around $70-100 for the batteries, you are looking at a grand total of $950 - $1130 for a homemade system.

    400-Watts for about $1000. However, you can make the system as powerful as you need. It will cost you, but will cost you exponentially less than these prefab kits. It just takes a little bit of work.
    Since I'm not an electrical genius, I've got a question.

    Are you saying that I can get a 60w panel to charge however many batteries (within reason) that I need and with a 400w converter I can tap up to 400w out the batteries?

    Any suggestions on a source for the equipment?
    The difference between stupidity and ignorance is that ignorance is a choice.

  9. #9
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    I've done quite a bit with solar and am not a big fan of building panels. The biggest issue is sealing them. Shopping around can find you some decent deals right now on equipment. Especially panels.

    There are some sizing factors that come into play when determining your needs. One of the most important is just what kind of loads. Once you determine that you can size inverter and battery bank. I found in my case I over estimated my need.

    If you are looking for a setup that will power some lights (use CFL bulbs), TV and refrigerator you can do so with a small inverter.

    This is setup I just finished putting together for a friend:

    Xantrex ProWATT 600 Sinewave Inverter $160 + SH
    2 x 190w 12v Solar Cynergy Panels 2 @ $330 + SH
    MorningStar ProStar 30A Charge Controller $145 + SH
    30A automatic transfer switch $60 + SH
    Costco 6v 200Ah batteries 2 @ $80
    Wire, connectors and aux breaker panel ~ $100

    This setup will be installed in a small off-grid cabin. The transfer switch is for his generator.

    Couple of rules of thumb. Batteries can only charge at a max of 13% of 20 hr Ah rating. So a 200Ah battery can take a max charge of 26 Amps. The panels listed above max at 11A each.

    Solar should be a minimum of 100w per 100Ah battery. So in the system above one panel would be acceptable but would not be able to charge the battery at max rate allowed.

  10. #10
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    Thanks V.

    I was looking around at the panels/individual cells last night and was pointing to going with the panels. I'm mechanically inclined but I don't know that this is something I'd want to tackle my first time out.
    The difference between stupidity and ignorance is that ignorance is a choice.

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