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Thread: Life expectancy of PV panels

  1. #11
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    It's the lifetime of inverters that matters.

  2. #12
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    Quote Originally Posted by gadfly56 View Post
    I can't see how that makes any sense. Unless you have a storage system and are completely off grid and depend on the output being at a certain level to meet your electrical needs, at least on an average basis, what is the driver for replacement? At 25 years, the panel costs are fully sunk and whatever your're getting really is free. Why incur capital costs at this point? For what kind of gain? 10% or 15%? That would never meet any kind of reasonable ROI.
    I think you are basically correct. Except for people with money who are looking to drastically increase their consumption. (e.g. 'I bought a house that already had a solar system, but it's too small for me') Also at the utilty scale there will probably be cases where overhauling arrays with new panels makes sense, since more is invested in the rest of the plant. I have always thought that at some point there would be a robust market for used PV panels discarded by such people. But we're only ten years into installation of PV at scale, so we probably have at least another decade until that would take off.

  3. #13
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    Quote Originally Posted by gadfly56 View Post
    I can't see how that makes any sense. Unless you have a storage system and are completely off grid and depend on the output being at a certain level to meet your electrical needs, at least on an average basis, what is the driver for replacement? At 25 years, the panel costs are fully sunk and whatever your're getting really is free. Why incur capital costs at this point? For what kind of gain? 10% or 15%? That would never meet any kind of reasonable ROI.
    Your description of our system is exactly right. We run 'off grid' about 99% of the time, we have the grid but generally only switch the house to the grid (completely bypassing the Tesla system) when we use our electric clothes dryer, and the 21 panels we have on the roof are more than enough to fully recharge the Tesla battery in moderately bright light, not necessarily direct sun, ususally by 1-2pm of afternoon, sometimes as early as 11:30 if it's summer and clear out. We love it.

    I think you and several other posters answered my question regarding life expectancy from today's brand of PV panels, so thank you very much for your input.

  4. #14
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    Thanks to everyone who replied to my question. I think I have a much better idea now what to expect. For the poster who asked about the Tesla Roof, sorry about my off-topic reply. I didn't know there was a "Tesla Roof" item, I thought you just meant a roof full of PV panels feeding a Tesla system.

  5. #15
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    Quote Originally Posted by caribconsult View Post
    Your description of our system is exactly right. We run 'off grid' about 99% of the time, we have the grid but generally only switch the house to the grid (completely bypassing the Tesla system) ...
    I believe that here is a way to program the Tesla Energy Gateway to do that automatically. It won't connect you to the grid until your usage exceeds what you can get from the batteries. It's tied to the unfortunately worded term "self consumption". It doesn't mean you are eating your leg.

  6. #16
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    I'm pretty sure there are solar panels on satellites that have been producing power since the 1960s.

  7. #17
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    Quote Originally Posted by ggunn View Post
    I believe that here is a way to program the Tesla Energy Gateway to do that automatically. It won't connect you to the grid until your usage exceeds what you can get from the batteries. It's tied to the unfortunately worded term "self consumption". It doesn't mean you are eating your leg.
    According to my conversations a few months ago with Tesla's chief engineer in the Caribbean, the ability to turn off the 'sell back' function is not yet part of the PowerWall2 system, but it is something they are considering. That would indeed allow us to stay connected full time to the grid without selling back anything and thereby putting an error message on our meter, which the electric co. can see from their office - and I don't need them coming around asking questions. Since we are not full-time connected to the grid and only connect when it's on, our system poses no danger to their linemen, which is what they say they are concerned with regarding private generation of any kind, solar, gas or diesel.

    But realistically speaking, we use the grid so infrequently, perhaps once a week for laundry, that it's not a big pain in the you know what to manually turn it on or off. Just one breaker does it. I had a very thorough discussion with the electrician that did our install and he set it up so we can use the grid, the generator or the PV array at any time and control the flow of all of this via a series of breakers and switches. Mostly fully automatic and works well. The installer did an excellent job. Maybe one day I'll hear from their engineer that they've resolved the sell-back function control. I'll keep you posted!

  8. #18
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    Here is some long term experience in Scottsdale AZ:

    1995: Installed a PV system with 40 ea 75W Siemens (ex Arco Solar) modules (3000W) with two Trace SW4024 inverters with batteries, but utility connected.

    2007 New owner, poor performance of the system. Inverters and modules out of warranty. Two problems: Inverter setpoints drifting such that one inverter was selling to the utility because battery was full charge voltage, other inverter was charging the battery, even from the utility at night. Adjusted setpoints, but same problem developed. Owner decided to replace the two inverters with one SW3000 and of course no battery. In rewiring the array to 20 series modules and checking the modules, found that about half of the modules were degraded to about 50% of initial power. No similar size modules available, so repositioned to make two strings of modules, one "good", one "poor". Noted that the "poor" modules were much darker backskin.

    2017: Addition to the residence. Essentially no output out of the "poor" string that was in parallel with the "good" string on the single input inverter. Installed 16 ea 300W PV modules (4800W) in the original area and 7200W on the addition. Old PV modules were donated to the PV testing lab at Arizona State University as they were interested in the differences between "good" and "poor" modules.

  9. #19
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    Quote Originally Posted by BillK-AZ View Post
    Here is some long term experience in Scottsdale AZ:

    1995: Installed a PV system with 40 ea 75W Siemens (ex Arco Solar) modules (3000W) with two Trace SW4024 inverters with batteries, but utility connected.

    2007 New owner, poor performance of the system. Inverters and modules out of warranty. Two problems: Inverter setpoints drifting such that one inverter was selling to the utility because battery was full charge voltage, other inverter was charging the battery, even from the utility at night. Adjusted setpoints, but same problem developed. Owner decided to replace the two inverters with one SW3000 and of course no battery. In rewiring the array to 20 series modules and checking the modules, found that about half of the modules were degraded to about 50% of initial power. No similar size modules available, so repositioned to make two strings of modules, one "good", one "poor". Noted that the "poor" modules were much darker backskin.

    2017: Addition to the residence. Essentially no output out of the "poor" string that was in parallel with the "good" string on the single input inverter. Installed 16 ea 300W PV modules (4800W) in the original area and 7200W on the addition. Old PV modules were donated to the PV testing lab at Arizona State University as they were interested in the differences between "good" and "poor" modules.
    Yikes! That sounds like a nightmare system, but since it was installed so long ago, there have been many changes in technology. Some upgrading might be in order. One of the features we like about the system we have is that each panel has its own microinverter (Enphase) so if one inverter or panel goes down, the array continues to function at about 95% output. They (The installer in collaboration with Tesla) also gave us, free of charge, an Enphase Envoy, a very sophisticated monitoring system for the PV and microinverter sections that allows you to monitor each panel/inverter combo individually, so if one goes off the rails you can spot it immediately. This Envoy was not part of our original purchase but they put it in to help resolve some issues we had at first. I think more and more installers are now making it a mandatory part of a modern system.

    I like the sound of 300w panels! That gives you some serious boost in available energy. What sort of batteries are you using?
    Last edited by caribconsult; 02-07-19 at 01:05 PM.

  10. #20
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    Quote Originally Posted by caribconsult View Post
    Yikes! That sounds like a nightmare system, but since it was installed so long ago, there have been many changes in technology. Some upgrading might be in order. One of the features we like about the system we have is that each panel has its own microinverter (Enphase) so if one inverter or panel goes down, the array continues to function at about 95% output. They (The installer in collaboration with Tesla) also gave us, free of charge, an Enphase Envoy, a very sophisticated monitoring system for the PV and microinverter sections that allows you to monitor each panel/inverter combo individually, so if one goes off the rails you can spot it immediately. This Envoy was not part of our original purchase but they put it in to help resolve some issues we had at first. I think more and more installers are now making it a mandatory part of a modern system.

    I like the sound of 300w panels! That gives you some serious boost in available energy. What sort of batteries are you using?
    We spec the Envoy in every Enphase system we put together; we are hopeful that we will be able to get Enphase micros again before too very much longer.

    My company has a partnership with SunPower; SP just announced a 400W residential module, and there are 395W commercial modules rolling out soon.

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