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

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      #17
      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!

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        #18
        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.

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          #19
          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, 01:05 PM.

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            #20
            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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              #21
              Awesome! I think Enphase makes some quality stuff and they stand behind it. I have had nothing but good things to say about their Caribbean support team...they have been 100% helpful. For reasons unknown, the Envoy would not connect to my house wifi to get on line and report the data...well, it would and it wouldn't...connected and disconnected erratically. I finally did away with the wifi link by putting an EOP adaptor right in the Envoy box where there's a receptacle just for it, and using that to get to the router at the other end of the house. Works perfectly and connected itself as soon as I plugged it in. I don't know how much better than that you could do.

              It's good to hear that bigger and more powerful solar panels are emerging. All of it...batteries, controllers, inverters, etc, will get cheaper and better as time goes on, because it's the future for many, particularly those that get a lot of sun, as we do. Use it!

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                #22
                Originally posted by ggunn View Post
                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.
                Are these 395/400 watt modules occupying the same footprint as the 75 watt modules mentioned from 1995?

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                  #23
                  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 agree with you from an investment standpoint, and certainly the majority of people have that in mind when investing in a PV system, but lets remember people do things for different reasons. As an example, for myself, I hate monthly recurring payments. Makes me feel like a slave. I have money now, I am healthy and have work and can work. I would rather invest in a solar system now and not have to worry about a monthly electric bill for the next 30 years. It makes me feel more flexible and secure.
                  Ethan Brush - East West Electric. NY, WA. MA

                  "You can't generalize"

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                    #24
                    Originally posted by gadfly56 View Post
                    Are these 395/400 watt modules occupying the same footprint as the 75 watt modules mentioned from 1995?
                    They are probably 2-3 times the area (per panel, not array). i.e also 2-3 times more efficient.

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                      #25
                      Originally posted by BillK-AZ View Post
                      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.
                      so there are studies out there then.....~RJ~

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                        #26
                        Originally posted by gadfly56 View Post
                        Are these 395/400 watt modules occupying the same footprint as the 75 watt modules mentioned from 1995?
                        The 395W commercial modules are 81.4" X 38.9". I don't know the dimensions of the 400W residential ones.

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                          #27
                          Originally posted by ggunn View Post
                          The 395W commercial modules are 81.4" X 38.9". I don't know the dimensions of the 400W residential ones.
                          What were the old 75 watt panels? I'm trying to understand how much more roof real estate is involved.

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                            #28
                            Originally posted by gadfly56 View Post
                            What were the old 75 watt panels? I'm trying to understand how much more roof real estate is involved.
                            I have no idea; they were before my time in the industry.

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                              #29
                              Originally posted by ggunn View Post
                              I have no idea; they were before my time in the industry.
                              In 2001, we installed lots of 100 or 110 watt panels.
                              26x58 inches = 10.47 square feet.
                              100W/10.5 sq ft = 9.5W / sq ft


                              Today, panels are 39x66" = 17.88 square feet.
                              Newest panels are 320 W. (premium SunPower and LG panels will be 365W......... i believe)
                              320W/17.9 sq ft = 17.9W / sq ft

                              In 18 years, panel efficiency has gone up (17.9/9.5 = 1.88) 90%

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                                #30
                                I bet the 75W panels were ARCO solar or Siemens and had circular cells or half circles. Just my WAG.

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