I want to do a side by side inverter comparison

heynow999
heynow999 Solar Expert Posts: 80 ✭✭✭✭
in General Solar Power Topics #1
I am looking to refine my ideas for doing a side by side comparrison for different inverters

I want to do this because I am an installer and I hear a lot of hype from the different manufacturers and I would like to see for myself which is the best. I have searched the internet for comparisons of inverters and really the only thing I found was Solar Guppys Home Power article from ten years ago! I dont have the money or time to do a module comparison, and because Photon magazine is doing module tests I don't see need to test modules.

The site is a 3500 sq ft flat roof near Toronto, Ontario. There is no shade. The system will be grid-tie, feed-in-tariff. My current idea is to use 42 Siliken 250watt modules. I would group them into 3 groups of 14 modules. One string would use Enphase m215 micro-inverters. A second string would use an SMA 3000HF inverter with Tigo. The third string would use just the SMA 3000HF inverter. I plan on using a Sunny webox and a Sunny Sensorbox.

Some ideas I have are to get the flash tests for each module and map each location.

Panel match the strings for the SMA inverters. Give the highest string to the SMA, the medium string to the SMA+Tigo and the lowest string to the Enphase?

I was thinking I would size the wire so all runs have the same voltage drops, or as close as I can get.

Any ideas?
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Comments

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #2
    Re: I want to do a side by side inveter comparison

    Since California started requiring UL certification of performance in late 2004, the need for such comparisons has basically vanished.

    You can look up the performance specifications here:

    http://www.gosolarcalifornia.org/equipment/inverters.php

    And the UL witnessed and or performed test results:

    http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries/

    I worked with with Xantrex under contract in 2004 to highlight the out right lies that manufactures were reporting ( I did extensive tests at the time on the five leading manufacture of GT equipment ), my data, along with others and manufactures that were at a disadvantage by the practice is what lead to the California UL requirement.

    The only piece missing is a deterministic method to test mppt tracking, but at this point I'd say the chances of a single array configuration finding an issue now is remote at best.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Re: I want to do a side by side inverter comparison
    heynow999 wrote: »
    The site is a 3500 sq ft flat roof near Toronto, Ontario.

    Very first thing that comes to mind is - - SNOW LOAD.
    Not only the snow that will build up on the panels, blocking light, but the potentially huge loads of snow the panels will catch and collect between them, snow that would otherwise tend to blow off the flat roof. This is something that I believe should be seriously considered.
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  • Fatawan
    Fatawan Solar Expert Posts: 71 ✭✭✭
    #4
    Re: I want to do a side by side inverter comparison
    heynow999 wrote: »
    I am looking to refine my ideas for doing a side by side comparrison for different inverters

    I want to do this because I am an installer and I hear a lot of hype from the different manufacturers and I would like to see for myself which is the best. I have searched the internet for comparisons of inverters and really the only thing I found was Solar Guppys Home Power article from ten years ago! I dont have the money or time to do a module comparison, and because Photon magazine is doing module tests I don't see need to test modules.

    The site is a 3500 sq ft flat roof near Toronto, Ontario. There is no shade. The system will be grid-tie, feed-in-tariff. My current idea is to use 42 Siliken 250watt modules. I would group them into 3 groups of 14 modules. One string would use Enphase m215 micro-inverters. A second string would use an SMA 3000HF inverter with Tigo. The third string would use just the SMA 3000HF inverter. I plan on using a Sunny webox and a Sunny Sensorbox.

    Some ideas I have are to get the flash tests for each module and map each location.

    Panel match the strings for the SMA inverters. Give the highest string to the SMA, the medium string to the SMA+Tigo and the lowest string to the Enphase?

    I was thinking I would size the wire so all runs have the same voltage drops, or as close as I can get.

    Any ideas?

    Be a real pioneer and try the Enecsys instead of the Enphase!
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #5
    Re: I want to do a side by side inveter comparison
    Solar Guppy wrote: »
    Since California started requiring UL certification of performance in late 2004, the need for such comparisons has basically vanished.

    You can look up the performance specifications here:

    http://www.gosolarcalifornia.org/equipment/inverters.php

    And the UL witnessed and or performed test results:

    http://www.gosolarcalifornia.org/equipment/inverter_tests/summaries/

    I worked with with Xantrex under contract in 2004 to highlight the out right lies that manufactures were reporting ( I did extensive tests at the time on the five leading manufacture of GT equipment ), my data, along with others and manufactures that were at a disadvantage by the practice is what lead to the California UL requirement.

    The only piece missing is a deterministic method to test mppt tracking, but at this point I'd say the chances of a single array configuration finding an issue now is remote at best.

    Thats some great information.

    What I really mean is I want to test micro inverter vs string inverter vs Tigo. I have seen one test that Tigo refers to on thier website, but other than that there is very little out there
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #6
    Re: I want to do a side by side inverter comparison

    With unobstructed array, the differences between the inverters performance will likely be impossible to measure as the differences to the arrays tolerances will be the dominate factor.

    Most of what the micro inverter manufactures use for selling features over string inverters is in shaded conditions, which by definition isn't where you put solar in the first place.

    You will also need very expensive, high precision power meters to independently tally harvest. The ones I have used are in the 10-20K range.

    Add it all up, its not really something for homer-owner or installer to set out to do.
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #7
    Re: I want to do a side by side inverter comparison

    Enphase claims to have %15 system losses while a string inverter is supposed to have %23. I think you would be able to see that difference from the output that the inverters report.

    As I mentioned, I also want to do it to gain experience with Tigo, which I have never installed.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #8
    Re: I want to do a side by side inverter comparison
    heynow999 wrote: »
    Enphase claims to have %15 system losses while a string inverter is supposed to have %23. installed.

    Enphase marketing slant

    In non-shaded configurations, a string inverter will have no deficiency to a micro panel inverter.

    Even with the 8% difference quoted, you can't rely on consumer level metering to measure the difference, most metering vendor provided is +- 5% and there is no regulatory requirements for precision.

    Its been my experience, that the manufactures that make such "I'm better than everyone" tend to have metering that reports on the postive side of that window. I know as I proved it, but I had to use certified calibrated lab power analyzer to make the measurements, which have a street price of over 20K.
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