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  • #16
    Hi BobJ - Welcome to Solar Panel Talk!

    Russ
    [SIGPIC][/SIGPIC]

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    • #17
      Cost of micro-inverters

      Originally posted by Sunking View Post
      No micro-inverters cost more per watt. They should only be used where shading or different orientation is a problem. Otherwise they are not justified.
      To the contrary, if the micro-inverter is reliable i.e. it's life is comparable to that of solar panels, the cost-per-watt that can be harvested over the life of the system, which is the real measure of return-on-investment, is reduced, typically by some 5 to 20%. Micro-inverters without electrolytic capacitors can demonstrably reach this level of reliability. By demonstrably, I mean subjecting the micro-inverters to the same accelerated life test that are used to test solar panels. If you use string inverters, you need to factor in replacing them a couple of times during the life of the system - few are warranted beyond 5 years and all use the dreaded electrolytic capacitors (although admittedly not in the severe environment of a rooftop). It is over-simplistic to just look at the initial hardware cost and rule out the use of micro-inverters on that basis.

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      • #18
        Great info

        I thought I had done my homework prior to investing in an Enphase based PV array, but I confess to never hearing about the electrolytic capacitor issue to which you refer. I hope the posters are wrong or perhaps exercising an abundance of caution, because there are tens of thousands of inverters poised for an early demise othewise.

        BobJ: do you have a relationship with Enecsys that should be mentioned in the interests of full disclosure? Your excellent post strays from analysis to advocacy.

        Mike: Are you suggesting that roof-top and space travel applications are similarly "tough einvoronments"
        SHF produces something besides manure!

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        • #19
          Micro-inverters

          Originally posted by silverhorsefarm View Post
          I thought I had done my homework prior to investing in an Enphase based PV array, but I confess to never hearing about the electrolytic capacitor issue to which you refer. I hope the posters are wrong or perhaps exercising an abundance of caution, because there are tens of thousands of inverters poised for an early demise othewise.

          BobJ: do you have a relationship with Enecsys that should be mentioned in the interests of full disclosure? Your excellent post strays from analysis to advocacy.

          Mike: Are you suggesting that roof-top and space travel applications are similarly "tough einvoronments"
          Silver Horse Farm,

          yes, I do have a professional relationship with Enecsys that I am happy to make public in the interests of full disclosure. However, the opinions expressed in my posts are entirely my own and based on research I have undertaken on the subject of micro-inverters. They are not representations made on behalf of Enecsys and are not endorsed by the company in any way. I'm an electronics engineer and have previously worked for several years in the electrolytic capacitor business so my knowledge of that particular subject goes back a long way. Like all new industries, there is a lot of hype and misunderstanding in solar PV. The nonsense surrounding the way some people misuse MTBF with respect to micro-inverter reliability is a particularly irritating example of marketing hype that imparts very little useful information - and that's the subject that triggered me to take part in this forum, rather than a desire to promote any specific company. Enecsys just happens to be one of the companies that takes a more technically robust approach to the subject.

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          • #20
            Electrolytic Capacitors

            BobJ: Thank you for your candor.

            This is a classic case of where the consumer is trapped beween various studies, each citing credible science and test-derived evidence by nobel laureate authors, each reaching a different conclusion. I do know that Enphase had to satisfy venture capital's due dilligence concerns over their choice of capacitor and apparently satisfied them. Regardless, I am reliably infomed that there is built-in redundancy so if one fails open, the inverter will continue to work. It sounds as if the spec calls for continuous operation at over 100C, so isn't there a comfortable margin built-in?
            SHF produces something besides manure!

            Comment


            • #21
              More on micro-inverters

              Silver Horse Farm,
              The basic issue with electrolytic capacitors is that they rely on a chemical reaction to maintain the dielectric layer (the insulating layer of aluminum oxide) throughout their operating lives. Chemical reactions are subject to variation in varying climatic conditions. Depending on where you live, the roof top can be a very extreme and unpredictable environment, particularly with respect to temperature. Nobody really knows how long these components can survive and their survival will depend on environmental conditions. However, you need to ask yourself two questions: why are many micro-inverter manufacturers making such huge efforts to remove electrolytic capacitors from their products if such capacitors cause no threat to reliability? Also, why won't micro-inverter manufacturers who use electrolytic capacitors warrant their products for more than 15 years or provide accelerated life test data to support their reliability claims? I'm sure there will be some installations that prove to be reasonably reliable, but would you deliberately put dozens (or hundreds) of mini-chemical reactions on your rooftop if a more benign alternative were available? Incidentally, talk to any radio or electronics hobbyist who likes to restore vintage equipment. The very first thing they do is replace all the electrolytic capacitors.

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              • #22
                I am not too impressed with the 'due diligence' of the VC bunch. At present one of the big names is Vinod Khosla and from the biofuel projects he has backed I wonder what kind of a dart board he has and he really should replace it.

                I believe the due diligence amounts more to the company getting the product to market and the VC getting out with big bucks before it all goes down the toilet.

                Another widely hyped VC is Google - again, a lot of the stuff they have backed defies any attempt at understanding what they were thinking.

                Bob is 100% correct that the companies should provide accelerated testing results if they really want people to buy into their argument.

                Russ
                [SIGPIC][/SIGPIC]

                Comment


                • #23
                  Originally posted by silverhorsefarm View Post
                  Mike: Are you suggesting that roof-top and space travel applications are similarly "tough einvoronments"
                  No, roof top is much more harsh !

                  Gear for space flight is very carefully built so that there is as little as possible thermal stress. There are heaters in shaded areas, and thermal mass that moderates the hot cold cycles to be very benign.
                  But being that we can't repair much of it, only the very best stuff is used, and it's well tested beyond infant failure, so that it can run for 20 years. Sometimes this works out really well (the Mars rovers, designed to run 6 months and lasted over 2 years) and sometimes a bad part gets into a power supply and kills the whole bird. (several commercial telecom sats)
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #24
                    One reason people decide to go with microinverters is because their solar system will be built in phases. If you plan on adding onto your solar system in the future, you won't need to buy a larger inverter, just more microinverters. Also, I've heard back from some customers that they really like their Enphase monitoring system. Here's a demo:

                    HTML Code:
                    http://www.enphaseenergy.com/products/moreinfo/enlighten.cfm
                    It might take a while to load, but it's pretty cool.

                    Comment


                    • #25
                      I work for a solar company and almost 100% of our installs use enphase inverters.
                      I understand the hesitancy of some as this is fairly new technology ( The concept has been around for a long while though despite rather dramatic early failure rates) I am not qualified to comment on the variety of capacitors used in various units however I do know the following to be fact.
                      There has been a reasonably large rate of change in module manufacture with manufacturers deleting and adding new modules. What happens when you have a defective or damaged module that has been discontinued? If a module cannnot be found with almost exact electrical properties a string inverter could have harvest seriously efffected dure to mismatch.
                      If a problem occurs with a module on a large flush mount array with a string inverter how much more labor will it take to find the fault as opposed to getting an e mail from Enphase highlighting exactly where to find the problem.
                      The above advantages along with increased energy harvest seem to make micro inverters a no brainer.
                      We have also installed several hundred over the past year and a half and have had only two failures. One was on install the other occurred about 6 months after.
                      NABCEP certified Technical Sales Professional

                      [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                      [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                      [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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                      • #26
                        great info

                        I hope others with experience (good or bad) with micro-inverters or micro MPPT , Enphase , solaredge or otherwise post here.

                        While no long term real life testing is out there to the degree it is on more established technology, even seeing the initial bath tub curve early life fails is interesting to see.

                        In 2 months or so when the snow melts, I will be installing the solaredge powerboxes and central inverter on a 4.4kw system and I will report any and all useful observations here.

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                        • #27
                          Looking forward to your project results - when the white stuff goes away.

                          Russ
                          [SIGPIC][/SIGPIC]

                          Comment


                          • #28
                            Ted 5002

                            FYI.. While the solaredge has monitoring via their web portal.. i wanted to monitor my usage as well so I just ordered a TED-5002C (yea.. i got the silly zigbee wireless display that folks have mentioned issues with.. ).

                            My hope is to install it before I get any solar work done and get it working and even monitor a circuit or two in addition to the overall usage.

                            I have shaved all the electricity usage I can think of ( unplug tvs / cable boxes when not in use , all lights CFLS..) and I don't seem to be making my #s much smaller. Approx 10 kwh / day seems to be the bottom for me unless I get a new fridge and perhaps washer (13 yr old top loader) / dryer (gas).. The fridge is using 2wh / day or so now.. but in summer with the house hotter than the 58F it is now, I suspect it will go up significantly.. If it would die. i'd be all set.


                            Net.. anyone like / hate the TED? I didn't mean to hijack and feel free to put elsewhere if you know where.. I figured I will roll it into the cost of the system come fed tax credit time so for $200, why not?

                            Comment


                            • #29
                              Originally posted by vtkahns View Post
                              .....The fridge is using 2wh / day or so now.. but in summer with the house hotter than the 58F it is now, I suspect it will go up significantly.. If it would die. .....
                              You mean your fridge is using 2KWh a day ? Kill it. New 20cf energy star fridges are in stores now, for $900. use about 1,000wh, about half of yours.
                              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister

                              Comment


                              • #30
                                Fridge or not to fridge

                                Originally posted by Mike90250 View Post
                                You mean your fridge is using 2KWh a day ? Kill it. New 20cf energy star fridges are in stores now, for $900. use about 1,000wh, about half of yours.
                                The problem i have with getting a new one is that if I save 500 kwh / year.. at $0.14/ kwh.. that's $70 / year savings.. more than 10 years to pay for the fridge.. which I am told may not even make it 10 years.. so.. when is the right time to do it ?

                                The new 25 cf (what we have now and I wouldn't want to go much smaller) ones I have peeked at do indeed use 5-600 kwh / year rating vs my 1000 kwh / yr (per the sticker ) .

                                Just not something I want to do right now with the out of pocket cost of the PV system about to hit me in a couple of months... and then wait a year for my fed tax credit of 6K.

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