Homemade Solar Panels?

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:confused: Do you need any permits for using homemade solar panels vs commercially bought ones? :confused: Thanks in advance. :D
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Homemade Solar Panels?

    You can not use home-made panels on a grid-tie install. They are not UL listed, and no inspector or insurance underwriter is going to approve them.

    Since it is not possible for someone to make a panel themselves that is as safe as a commercially produce unit, this is a good thing.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    I am not quite sure what question you are asking...

    If you are building a small off-grid solar system, there are no permits at all required.

    If you are building a home/cabin and intend to insure it--Then, technically, the solar panels (and the rest of the hardware) should be "Listed" by a NRTL (Nationally Recognized Testing Laboratory--Like UL, CSA, ETL, TUV, etc.)... They are not so much required by a government body, but by your insurance company (they may choose to not pay out on a claim if unlisted panels and other code avoidance mistakes are made).

    If you are doing a Grid Tied system (connected to the utility power)--Then normally a building department and utility requirements will come into play. And then, it will be virtually impossible to "legally" use home made panels on your system. The building inspector and utility are supposed to make sure that the installation complies with current building codes.

    Could you build and install with home made panels and get away with it... Probably. It would all depend on how knowledgeable and thorough your inspectors are.

    Here is one such installation (Panel Fire Question thread) that was apparently installed by a licensed contractor and approved by a major city's building department.

    Still caught fire (probably be cause of non-listed solar panels).

    But, on the other hand, there have been fires caused by properly Listed and Inspected solar systems too (wires can arc / short and still start a fire). Listing/NRTL/NEC requirements are there to reduce the chances of fire (and spread of fires)--But cannot eliminate them.

    From a practical point of view--Very few people have the material and equipment plus training to build panels that will last 10-20+ years out in the sun and weather. Generally, from what I have seen here, home made panels may last a few months to a year before they start failing.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    You can not use home-made panels on a grid-tie install. They are not UL listed, and no inspector or insurance underwriter is going to approve them.

    Since it is not possible for someone to make a panel themselves that is as safe as a commercially produce unit, this is a good thing.

    BB. wrote: »
    I am not quite sure what question you are asking...

    If you are building a small off-grid solar system, there are no permits at all required.

    If you are building a home/cabin and intend to insure it--Then, technically, the solar panels (and the rest of the hardware) should be "Listed" by a NRTL (Nationally Recognized Testing Laboratory--Like UL, CSA, ETL, TUV, etc.)... They are not so much required by a government body, but by your insurance company (they may choose to not pay out on a claim if unlisted panels and other code avoidance mistakes are made).

    If you are doing a Grid Tied system (connected to the utility power)--Then normally a building department and utility requirements will come into play. And then, it will be virtually impossible to "legally" use home made panels on your system. The building inspector and utility are supposed to make sure that the installation complies with current building codes.

    Could you build and install with home made panels and get away with it... Probably. It would all depend on how knowledgeable and thorough your inspectors are.

    Here is one such installation (Panel Fire Question thread) that was apparently installed by a licensed contractor and approved by a major city's building department.

    Still caught fire (probably be cause of non-listed solar panels).

    But, on the other hand, there have been fires caused by properly Listed and Inspected solar systems too (wires can arc / short and still start a fire). Listing/NRTL/NEC requirements are there to reduce the chances of fire (and spread of fires)--But cannot eliminate them.

    From a practical point of view--Very few people have the material and equipment plus training to build panels that will last 10-20+ years out in the sun and weather. Generally, from what I have seen here, home made panels may last a few months to a year before they start failing.

    -Bill

    It would be Grid-tied. So what kinds of things would be needed and what extra cost would there be?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    What are you asking about? A Grid Tied inverter, or all of the supporting stuff (UV rated wiring, MC4 connectors, combiner boxes/fuses/breaker, main disconnects, how to size the main service panel to add GT solar or what?

    Building permits, various state laws and regulations about GT solar and billing issues/questions?

    There are a couple of threads here with lots of details about installing GT systems with lots of photographs.

    People are paying around ~$6-$8 per watt, installed turnkey systems, depending on the details and where they live. You can get a 30% fed tax rebate and there are many state and local rebate programs too. Many of the state/local rebates require contractor installs and building permits:

    DSIRE

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    BB. wrote: »
    What are you asking about? A Grid Tied inverter, or all of the supporting stuff (UV rated wiring, MC4 connectors, combiner boxes/fuses/breaker, main disconnects, how to size the main service panel to add GT solar or what?

    Building permits, various state laws and regulations about GT solar and billing issues/questions?

    There are a couple of threads here with lots of details about installing GT systems with lots of photographs.

    People are paying around ~$6-$8 per watt, installed turnkey systems, depending on the details and where they live. You can get a 30% fed tax rebate and there are many state and local rebate programs too. Many of the state/local rebates require contractor installs and building permits:

    DSIRE

    -Bill

    I'm talking about certifications and permits for diy solar
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    UL Listing for a solar panel takes around 6 months and costs ~$50,000 plus yearly fees and 1-2 unscheduled inspections per year of the mfg. facility (may be more for Listed product--the inspections where for Registered products like computer systems and such).

    There was an interest article about UL testing of solar panels from the San Jose Mercury posted by "Russ" at the beginning of the year. For me, this was an interesting data point and may actually show that UL (and other NRTL's if they follow similar testings procedures) are at least doing some basic quality testing of the panels:

    $50,000 and 6 months of testing to pass a panel.
    Chris Paxton, who manages much of the solar testing at the lab, says the majority of "failures" occur with the "humidity freeze" test. The panels go through a 10-day testing cycle where they are exposed to 85 percent humidity — much like the environment in the tropics. Wet modules are then brought down to frigid temperatures of negative 40 degrees Celsius, where the moisture freezes and expands. UL technicians then scour the panels for any defects or inconsistencies in construction.
    That sounds like a very difficult test to pass.

    The off-grid requirements would tend to be local... If for a personal cabin--probably nobody around to check it out. If you want to insure--perhaps the insurance company will send somebody out to photograph and (possibly) inspect the property (they are starting to do that more and more in the "big cities"--A neighbor of a friend failed a curbside inspection (dying/dead large trees in the back yard--Was told to remove trees or loose insurance. Another was told to paint, re-putty windows, and install new gutters, etc.).

    Perhaps some people here with off-grid homes can discuss the issues they have with getting property/liability insurance... Not the easiest thing to do now (from the little I have seen here with previous posts).

    Of course, DIY solar covers a bunch of stuff---For example, solar thermal (hot water, hot air) lends itself very nicely to home made panels and self installed systems. The down side is the plumbing can be an issue in its own right (leaks, air locks in circulating loops, freeze ups, antifreeze failure from over temperature, incorrectly mounted pumps, too small of pressure tank (for excess coolant/water storage when system heats up, etc.).

    I can give you some links if that is of interest.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Homemade Solar Panels?

    tomas,
    is there an ultimate reason for all of this, like you wish to make homemade pvs for sale or is it just for your home that you wish to make some for? as was mentioned by bb, the pvs are hard to make equal to that made commercially and to do it for the same costs is unheard of so it is easier to just get the commercial pvs. there's nothing wrong with trying to build them yourself, but as i told you in a pm that it may not pass inspection without certification even if you do succeed at equaling commercial quality and costs to make them. that certification only pays off if one is marketing mass quantities and can absorb the high certification costs.

    i don't know if they'd need to be certified if only mounted away from any structures on pole or ground mounts. maybe one of the guys more familiar with that aspect of the nec could chime in on that.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
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    Re: Homemade Solar Panels?

    Spammer ... Like the CEO of Sun Power wants tips on DYI solar panels :roll:

    Spammers are working over time to get into Forums ... fake polls , asking pointless questions ect
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    BB. wrote: »
    UL Listing for a solar panel takes around 6 months and costs ~$50,000 plus yearly fees and 1-2 unscheduled inspections per year of the mfg. facility (may be more for Listed product--the inspections where for Registered products like computer systems and such).

    There was an interest article about UL testing of solar panels from the San Jose Mercury posted by "Russ" at the beginning of the year. For me, this was an interesting data point and may actually show that UL (and other NRTL's if they follow similar testings procedures) are at least doing some basic quality testing of the panels:

    $50,000 and 6 months of testing to pass a panel.


    That sounds like a very difficult test to pass.

    The off-grid requirements would tend to be local... If for a personal cabin--probably nobody around to check it out. If you want to insure--perhaps the insurance company will send somebody out to photograph and (possibly) inspect the property (they are starting to do that more and more in the "big cities"--A neighbor of a friend failed a curbside inspection (dying/dead large trees in the back yard--Was told to remove trees or loose insurance. Another was told to paint, re-putty windows, and install new gutters, etc.).

    Perhaps some people here with off-grid homes can discuss the issues they have with getting property/liability insurance... Not the easiest thing to do now (from the little I have seen here with previous posts).

    Of course, DIY solar covers a bunch of stuff---For example, solar thermal (hot water, hot air) lends itself very nicely to home made panels and self installed systems. The down side is the plumbing can be an issue in its own right (leaks, air locks in circulating loops, freeze ups, antifreeze failure from over temperature, incorrectly mounted pumps, too small of pressure tank (for excess coolant/water storage when system heats up, etc.).

    I can give you some links if that is of interest.

    -Bill

    $50000! No wonder solar panels cost so much. So you would have to pay that to use them yourself or sell them to other people? Like what if I made a small power plant of homemade solar panels?
    niel wrote: »
    tomas,
    is there an ultimate reason for all of this, like you wish to make homemade pvs for sale or is it just for your home that you wish to make some for? as was mentioned by bb, the pvs are hard to make equal to that made commercially and to do it for the same costs is unheard of so it is easier to just get the commercial pvs. there's nothing wrong with trying to build them yourself, but as i told you in a pm that it may not pass inspection without certification even if you do succeed at equaling commercial quality and costs to make them. that certification only pays off if one is marketing mass quantities and can absorb the high certification costs.

    i don't know if they'd need to be certified if only mounted away from any structures on pole or ground mounts. maybe one of the guys more familiar with that aspect of the nec could chime in on that.

    Well I did want to sell them and use them for myself. I guess I could make some of my house powered by solar and instead of using my power in my whole house I would use it to power certain parts of my house. It only seems that you should be able to make your own solar panels for yourself, but I guess the government wants to keep the big businesses up and running so they can get their money!
    Spammer ... Like the CEO of Sun Power wants tips on DYI solar panels :roll:

    Spammers are working over time to get into Forums ... fake polls , asking pointless questions ect

    I am doing this out of interest, not for spam. If you wish to think that way that is fine, but I know my intentions. Do you know who I am? No.

    Edit: I just saw your picture, sorry I didn't see it earlier.:p But no, that is not me. If you really want to see my picture, do a video chat with me.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?

    You will not do a grid-tie system with home made PV panels.

    They are not listed and will not pass inspection. If they don't pass inspection then the utility won't let you hook them up to their grid.

    If you bootleg it in and the utility finds out (and they will eventually), they'll disconnect your property from their grid and you'll be in the situation of having to run your whole property from your home made PV panels.

    It
    will
    not
    happen.
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    dwh wrote: »
    If you bootleg it in and the utility finds out (and they will eventually), they'll disconnect your property from their grid and you'll be in the situation of having to run your whole property from your home made PV panels.

    I'm guessing that by bootleg you mean power some parts of my house by solar, then I do not get why that would be a bad thing. If it is because they want my money, do they expect to get more money by disconnecting me?
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    I'm guessing that by bootleg you mean power some parts of my house by solar, then I do not get why that would be a bad thing. If it is because they want my money, do they expect to get more money by disconnecting me?

    No. By bootleg I mean - tying home made PV panels TO THE GRID.

    The grid belongs to the utility. You cannot feed power to the grid without permission. Period. You won't get permission unless the system passes inspection. You will not pass inspection with home made PV panels.

    They will disconnect you because your home made system is not approved, permitted, inspected and SAFE. It isn't about the money, it's about letting some hobbyist hook something UNSAFE to the grid.


    You can of course install a separate breaker panel and split whatever circuits off you want and power them however you want - it just can't be connected to the grid.

    And don't let your insurance company find out...
  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
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    Re: Homemade Solar Panels?

    No, by bootlegging he meant if you go on and grid-tie your DIY panels without utility's approval. Myself I don't quite see why utility should even care how you generate your DC. As long as inverter is UL approved and will disconnect during grid failure to prevent killing linemen, why should they care what happens on the DC side of the inverter? It's probably a liability thing for them, since they cannot verify your electrical competency, so the blanket rule is established: no UL = no GT.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    In California, they have the right to charge you "leaving the grid". Stranded Generation charges based on the fact that the utility, state, and bond holders have made loans to power suppliers (and distribution costs) in "your name"... And if you take the property "off grid"--they can bill you for the privilege.

    The whole GT Solar system is written as an exception to the general charging for stranded generation costs.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    AntronX wrote: »
    Myself I don't quite see why utility should even care how you generate your DC. As long as inverter is UL approved and will disconnect during grid failure to prevent killing linemen, why should they care what happens on the DC side of the inverter? It's probably a liability thing for them, since they cannot verify your electrical competency, so the blanked rule is established: no UL = no GT.

    I think it's probably more of a code thing. They don't want anything connected to the grid which is not to code, and the only way they can be sure of that is if the building and safety inspector signs off on it.

    And the inspector is simply not going to sign off on home made panels.

    As for what happens on the DC side of the inverter - if the NEC didn't care, then the inspector and the utility probably wouldn't care either.
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?

    Ok so powering SOME of my house while it is NOT connected to the grid is perfectly legal right, like if I had a transfer switch.

    P.S. I'm sorry if it sounds like I'm yelling, I'm just trying to emphasize what I mean.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    Yes--Nobody is going to come to your home and inspect what you do (as long as you do not connect to the grid and turn the meter backwards).

    How much power (Watt*Hours per day) do you need (by season), and roughly where will the system be installed. We can plug in the numbers for an estimated system design pretty quickly.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?

    I don't know my usage (sorry) but my zipcode is 48473. Just tell me if you need more.
  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
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    Re: Homemade Solar Panels?

    You already made some panels or just planning to?
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    Ok so powering SOME of my house while it is NOT connected to the grid is perfectly legal right, like if I had a transfer switch.

    If you use a transfer switch to disconnect your house from the grid, and switch over to your solar system, then your home made PV is *not* grid tied. Okay, good. Forget about grid-tie with home made panels - that simply will not happen.


    As for it being legit...probably not.

    When you flip the transfer switch to disconnect from the grid and connect to your home generating system - whatever it is, backup generator, solar, wind, whatever - your system is now considered a "separately derived system".

    Separately derived systems are covered in the National Electrical Code. Your local building codes will require that system to be compliant with the NEC.

    Which again, means permits and inspections. And that means you gotta sell it to the inspector. He won't buy it with home made panels.

    As long as it doesn't tie to the grid, the utility won't care - but the local building and safety department will.

    And your insurance company will. They frown on un-permitted and inspected electrical.

    P.S. I'm sorry if it sounds like I'm yelling, I'm just trying to emphasize what I mean.

    Doesn't bother me, I cap the odd word here and there all the time. Yelling is when you cap a bunch of words in a row.
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    AntronX wrote: »
    You already made some panels or just planning to?

    I made one that I plan to use hunting, to power a few lights with a small battery backup (because I need the lights when the solar panel wouldn't produce power.)
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?
    dwh wrote: »
    Separately derived systems are covered in the National Electrical Code. Your local building codes will require that system to be compliant with the NEC.

    So what would be compliant with the NEC? What would I need to do?
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    BB. wrote: »
    Yes--Nobody is going to come to your home and inspect what you do (as long as you do not connect to the grid and turn the meter backwards).

    Actually - they might. I've heard tell of building and safety departments using Google Earth to check for unpermitted additions.

    If an irritated neighbor drops a dime, then an inspector will definitely show up to check it out.

    Plus there is the "you never know" factor. Once I was helping a buddy form in a foundation to replace the chain link fence between his house and driveway with a wall, and an inspector saw us and stopped just to see what was going on. If we had been pouring a foundation for an add-on and he didn't have permits on file, he would have been cranky. Since all we were doing was pouring a footing for a wall, he didn't care.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?

    Get a Kill-a-Watt meter and/or a DC Amp*Hour / Watt*Hour meter to measure your loads... You cannot design/build a system to support unknown loads.

    Your other choice--Choose a solar panel wattage or a battery bank size, then design backwards/sideways to build a system that is relatively functional.

    For Flint MI... This is the hours of average sun per day:
    1, 2.69
    2, 3.79
    3, 4.30
    4, 4.99
    5, 5.42
    6, 5.56
    7, 5.43
    8, 5.34
    9, 4.77
    10, 3.83
    11, 2.41
    12, 1.79
    "Year", 4.19

    Some starting assumptions... Assume your off-grid system is 0.52 efficient (from solar panel rating to charge controller to battery bank to ac inverter to AC power at the outlet). If you tilt a 100 watt panel at latitude and assume 5+ hours of sun per day, you will generate:
    • 100 watts * 5 hours of sun * 0.52 derating = 260 WAtt*Hours (average) per day
    Say you have a nice sized laptop you want to run from your 100 watt panel every night... And it takes an average of 50 watts of power:
    • 260 WH per day / 50 watts = 5.2 hours per day (on 5+ hours of sun per day)
    A battery bank for a 100 watt panel (assuming commercially made)--the battery should be charged around 5-13% rate of charge (based on 20 Hour capacity). So:
    • 100 watt panel * 0.77 panel+charge controller derating * 1/14.5 volts charging * 1/0.13 rate of charge = 41 AH minimum battery @ 12 volts
    • 100 watt panel * 0.77 panel+charge controller derating * 1/14.5 volts charging * 1/0.05 rate of charge =106 AH maximum battery AH @ 12 volts
    The above are just rules of thumb we use around here for sizing a system... You don't have to follow them, but it is a good starting point to design/build a reasonably functional Off-Grid PV system.

    Feel free to plug in what ever numbers you want... The calculations are easy and intended to point you in the right direction.

    If you have more questions, please ask.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
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    Re: Homemade Solar Panels?
    dwh wrote: »
    As for it being legit...probably not.

    Highly doubt he will get in trouble with city for this. This is likely low priority on their to do list. But if panels get hit with direct lightning strike and burn the house down, the homeowner's insurance may use DIY panels as excuse to not pay out.
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?

    By 100 watt do you mean 100 watts coming from the solar panel or 100 watts of potential energy?

    BTW I'm a little confuzzled with the battery calculations.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    So what would be compliant with the NEC? What would I need to do?

    It's very simple; home made = hobbyist.

    To comply with code and sell it to an inspector, you MUST use approved and listed equipment. Period.


    I'm not down on home made PV panels. I think they are pretty cool, and I've seen pictures on the net of some very well done home made panels. But you have to keep that whole idea completely separate from "commercially made" PV panels.

    You can use your home made panels for portable hunting power - that's a neat way to use them. You could use them to power your yard lights - another neat way to use them.

    But they are a fire hazard, so don't even THINK about putting them on your roof.

    You could plant half a dozen in your yard, and run the power to a separate breaker box and power up some lights or whatever in the garage - as long as that "hobby" system does not connect to your "real" house wiring IN ANY WAY.

    Yes, you can do that. No, it's probably not going to comply with your local building codes, so you can "get away with it" - for how long...who knows. It would be pretty much the definition of "bootleg".
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Homemade Solar Panels?
    AntronX wrote: »
    Highly doubt he will get in trouble with city for this. This is likely low priority on their to do list. But if panels get hit with direct lightning strike and burn the house down, the homeowner's insurance may use DIY panels as excuse to not pay out.

    Yea as long as keeps it separate from the grid he's not likely to get into trouble unless something goes seriously wrong - like a fire or the neighbor's cat gets fried.

    Also of course, any non-compliant work will have to be brought up to code or ripped out if he ever sells the house. And possibly if he re-finances and some sharp appraiser/home inspector comes out to have a look.
  • thomaswarner
    thomaswarner Registered Users Posts: 24
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    Re: Homemade Solar Panels?

    Well that is kind of disappointing.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,468 admin
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    Re: Homemade Solar Panels?
    By 100 watt do you mean 100 watts coming from the solar panel or 100 watts of potential energy?

    BTW I'm a little confuzzled with the battery calculations.

    How much do you know about electricity and the basic math?
    • Voltage = Current * Resistance = I*R
    • Power = Watts = V*I = V^2 / R = I^2 * R
    • Energy = Power * Time = Power (Watts) * Hours
    Note that Energy = Watt*Hours is not an "SI" unit--The real SI unit is Watt*Seconds--but that would yield numbers 3,600x larger (an average monthly home power bill of 600 kWH would be 2,160,000 kWS).

    A 100 watt panel in perfect, cool, noon-time sun would be able to power a 100 watt light bulb. The derating factors are there to convert from "laboratory/Marketing" numbers to "real life" numbers.

    The real calculations are more complex and would need to take in a lot more factors--but are pretty much going to get you more accurate numbers but against the daily variability of the sun (clouds, temperature, seasons, etc.)--10% more accurate numbers are pretty much meaningless.

    However, you do have to be smart about selecting / operating equipment...

    A large multi-kWatt inverter can use upwards of 60 watts with no load on the AC output... A small 300 watt inverter will use 6 watts with no load on the output... A small 300 watt inverter with "search mode" (only turns on with an output AC load connected) will draw 0.6 Watts...

    So, choosing the "wrong" inverter could waste more power than your 100 watt array could produce in a full day of sun.

    Get the big picture first--Then look at a piece at a time to understand how the small picture stuff fits together with the big picture.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset