Solar Advice needed

Discussion in 'General Electronics Chat' started by ShockBoy, Dec 4, 2009.

  1. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    I am starting a long term solar panel installation at my house but I am starting with 108 cells, the standard e-bay ones 3.5a .5v and 1.75w each cell. My first question is beginning a long term project aquiring cells and building panels, how should I configure (series/parallel) these first panels so as to add to them accordingly in the future? 1400sqft house that on average uses 40kw per day. (which I will post another thread about inverters and wattage later) What is the best way to begin this project?
    Would like to eliminate electric bill is the goal. Off the grid would be nice but not necessary.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I'm wondering how many of your neighbors are stealing your power.

    40kw per day? :eek: That's a lot.

    Start by doing something with your hot water heating system and hot water usage. That's probably half of your electric bill.

    If your home insulation isn't up to snuff, that will cost you big money.

    If your water heater insulation isn't up to snuff, that will cost you at least as much money as your house insulation being substandard.

    Use more efficient lighting.

    It's a noble idea to "get off the grid", but you have to realize that a solar system will be very limited as to the power it can supply. Better start planning ahead how you can provide power with the limited resources that will be available.
     
  3. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    I have virtually no insulation at all. It's possible someone is jacking my power. I have a gas water heater. Already replaced the bulbs. I've already got the cells, enough for 3 panels.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, seems like you really need to work on getting that insulation in first - unless you're not using heating or A/C at all. You may be able to get some kind of tax incentives or rebates from the State and/or power company for upgrading your insulation, that will help offset the cost of installation.

    As far as lighting, consider going to low-voltage LED lighting. Otherwise, you'll need to use a power inverter to get DC battery voltage up to 120VAC; and that process is not 100% efficient.
     
  5. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    Gotcha. On a side note: How is this possible if the cells are rated at .5v each?
    Just checked on non broken cell and in california morning sun reads 1.1v

    Update: Low battery on the old volt-o-matic.
     
    Last edited: Dec 5, 2009
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Insulation first priority. What type of roof construction do you have? I have 10 in. rafters,3/8 decking[ouch] tar papper, dry-wall inside, with 4 in. glass. Romoved freese-boards [SP?], shover in an additional 5 in foiled fiberglass, painted roof white; big help with AC $. Think I would go with 12V[ 20V open ckt.] modules to use as low V applications, series 4 modules wher going to 48V invertor, parallel 48V strings for more power.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You connect the cells in series to increase the voltage output.

    If you wanted to be able to charge a 12v sealed lead-acid battery, you would need at least 14v output. 14/0.5 = 28 cells in series.

    However, you will only get 0.5v @ 3.5A output when the solar panels are directly perpendicular to the suns' rays at noon on a sunny day between June 25th and July 5th - or something like that.

    If you want decent performance from the array from an hour after sunup to an hour before sundown, you'll need a lot more planning and testing.

    Some installations use reflectors to multiply the intensity of the light on the solar arrays. Of course, this means that you need to cool the panels somehow; they lose efficiency as they get hot. Water is a very efficient conductor of heat. It will also corrode metal and freeze, so you need anti-freeze and corrosion protection.

    Having the array steer-able will help a great deal to maintain power output.
     
  8. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    So a max of 48v then parallel the remaining modules no matter how many I add?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Bernard mentioned a very cost-effective measure; painting the roof white.

    I was helping a friend remodel his home a number of years ago; the roof had dark grey shingles. It was hotter than blazes in the attic. We used a white roof coating over the shingles. The temp in the attic dropped 20°F-30°F.

    This is very easy to do, very inexpensive, and makes a great deal of sense. The darker your existing roof covering is, the greater your benefit will be.
     
  10. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    HaHaHaHa :):):)
    Looks like I might have gotten an upgrade on the cells I purchased.
    and an array is not out of the question. I am extremely good with my hands.
     
  11. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    Previously I had a rock roof (remember the 60's) Just put asphalt shingle roof on last year(by myself) and I have too many things plugged into the outlets here. Lotta people.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Don't get too far ahead of yourself. Right now, you don't even have a good idea of what your peak power requirements are.

    You need to first determine what your peak power requirements are, and then work on getting those peak power requirements reduced. You can do some of that simultaneously, by improving the efficiency of your A/C & heating systems, insulation, reflectivity of your roof, etc.

    Once you get your peak power requirements "nailed down", then you can explore what kind of inverter you will need, and what is available.

    You will also need a battery bank. What kind of bank you wind up with will be determined by what inverter meets your specifications/requirements, and preferably as efficient as possible. To produce 120VAC from 12v batteries requires a tremendous amount of current, meaning that you will have a lot of power loss in the cables. Going to a 24v, 36v, or 48v configuration reduces your current requirement by half, 2/3, and 3/4 respectively.

    Your battery bank will be quite expensive to purchase initially, and will probably have a maximum life of about 8 years if well-maintained. The more power you require, the larger and more expensive the battery bank will be.

    This is why you need to whittle down your power requirements as much as possible before jumping into settling on a design.
     
  13. ShockBoy

    Thread Starter Active Member

    Oct 27, 2009
    186
    0
    You are absolutely correct, however if I do not get started I will probably continue putting it off. Even starting with one or two panels and 2 or three batteries is fine with me right now. I know my power consumption needs to be researched, but for now I want to start. I'm not talking about going off grid tomorrow or anything.
     
  14. HarveyH42

    Active Member

    Jul 22, 2007
    425
    5
    The voltage is always higher without a load. If you put a resistor across the cell, the voltage will be closer to .5 volts. I haven't messed with individual cells, so couldn't suggest a value to try.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, so if you just want to start, then start researching batteries.

    You will probably be better off to use 6v (6.3v) deep-cycle batteries; they only have three cells each. If one cell in the battery fails, you just swap out the entire battery. This isn't as bad as having to can a 12v battery in which one of six cells has died. Besides, it provides more flexibility in configuration of your battery bank.

    Or if you want maximum flexibility, go for 2.1v deep-cycle cells. It'll be more expensive initially that way, and a lot more wiring, but if one cell fails, you just swap it out. You can also monitor performance across each individual cell.
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
     
  17. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    I reduced my electricity use to half by conserving and by replacing incandescent "heaters" with compact fluorescent light bulbs. My neighbour uses double the amount of electricity as me. She has her incandescent "heaters" on in sunshine!

    Recently I got a high efficiency natural gas furnace and air conditioner that will also save a lot of energy.
    The manufacturer was hungry so gave many rebates. My government also paid a lot of rebates for the furnace and air conditioner. They also supplied free compact fluorescent light bulbs.
     
Loading...