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Quick question solar energy system

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  • 18-12-2020 11:43am
    #1
    u2me
    Registered Users Posts: 100 ✭✭


    Looking into getting a small 1kw system to start out with which can be expanded overtime to 4kw.

    Would like opinions regarding the following:

    String inverters vs micro inverters: which to choose? I understand the difference but just wondering if micro is worth the additional investment, particularly regarding smaller systems.

    Also panels - considering LG panels but can anyone from experience recommend equivalent quality lower cost panels which are also worth considering?

    Thanks


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    #2
    unkel
    Registered Users Posts: 64,766 ✭✭✭✭unkel


    For a (very) small system, you could consider micro inverter(s), but if you are going to expand, I would go string inverter. If the max you will go is 4kwp, buy a 4kW inverter. It will work fine, and efficiently, with just 1kwp of panels. This is presuming you do not have shadow issues on the area you are going to install the panels.

    Don't spend any extra money on a brand name on a panel. It adds no value. The cheapest panels (per watt) that Irish distributors sell are perfectly fine for the job.


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    #3
    u2me
    Registered Users Posts: 100 ✭✭u2me


    Thanks - I was thinking a 3500w inverter just to have it slightly undersized. Obviously, the inverter will be significantly oversized till I got from 1 to 4kWp - hence why I was thinking of maybe going the micro route. But realistically I can't see it making that big a difference on such a small system.

    With regards to panels, the warranty giving on some of the lower budget ones is only 5 years whereas LG is 25 years. Have you any experience of how long the low budget ones last? I think maybe a lower-cost one with a 10-year warranty would do.

    The technology advances quickly enough and you would probably be likely to upgrade them after 10-15 years anyway I'd say.


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    #4
    slave1
    Moderators, Sports Moderators Posts: 18,687 Mod ✭✭✭✭slave1


    u2me wrote: »
    The technology advances quickly enough and you would probably be likely to upgrade them after 10-15 years anyway I'd say.

    Highly doubt it, in our two story semi I'm looking at leaving them there well past 15years, a lot of panels that generate more electricity compared to others is because of physical size not technology, panels remain around 19%-21% efficiency.
    Can't see them jumping to say, 50% given our path of progress to date and flattening of the improvement curve

    chart_solar_pv.gif

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    #5
    u2me
    Registered Users Posts: 100 ✭✭u2me


    No, they won't hit 50% but possibly 25/26% average which would equate to approx 20% improvement on output - Again though the benefits are scale related and so I suppose not such a big factor for smaller systems.

    Considering wear on lower-cost panels over time I'm just sceptical whether they will last past 15 years in Irish weather conditions? In a dry climate yes - wet like ours I'm just not so sure?

    Anyone have any long-term experience regarding the panels and how did they get on?


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    #6
    unkel
    Registered Users Posts: 64,766 ✭✭✭✭unkel


    u2me wrote: »
    Thanks - I was thinking a 3500w inverter just to have it slightly undersized. Obviously, the inverter will be significantly oversized till I got from 1 to 4kWp - hence why I was thinking of maybe going the micro route. But realistically I can't see it making that big a difference on such a small system.

    With regards to panels, the warranty giving on some of the lower budget ones is only 5 years whereas LG is 25 years. Have you any experience of how long the low budget ones last? I think maybe a lower-cost one with a 10-year warranty would do.

    The technology advances quickly enough and you would probably be likely to upgrade them after 10-15 years anyway I'd say.

    Panels last many decades, I wouldn't worry what "paper" warranty you are given with them. There is no technology advance on them, apart from them getting ever so slightly more efficient every year (perhaps half a percentage point per year at best)

    As for oversizing / undersizing - that's an old tale. These days inverters are very efficient whether you are loading them with 10% or >100% of their maximum capacity. So just get one that could handle the highest possible load you plan to install on it


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    #7
    slave1
    Moderators, Sports Moderators Posts: 18,687 Mod ✭✭✭✭slave1


    Even if their is a technological advancement of say 20%, you are going to be 20/25 years older by then and will the new investment ever pay off for you?
    Don't think too much on it, put up as many panels as you can afford and then forget about them, maybe I'm being too simplistic in that approach.

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    #8
    u2me
    Registered Users Posts: 100 ✭✭u2me


    Ok thanks, just trying to develop a spec for it at the moment is all hopefully later next year might try to get it together. I'm wondering would 2nd hand panels be an option worth considering?


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    #9
    slave1
    Moderators, Sports Moderators Posts: 18,687 Mod ✭✭✭✭slave1


    u2me wrote: »
    Ok thanks, just trying to develop a spec for it at the moment is all hopefully later next year might try to get it together. I'm wondering would 2nd hand panels be an option worth considering?

    Personally I would not go second hand when they are so reasonably priced new and come with long warranty

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    #10
    u2me
    Registered Users Posts: 100 ✭✭u2me


    Yep, the best option I'd say.

    It was just that I saw some branded ones on an auction site previously and it got me thinking maybe...

    Like you said when you can buy the budget ones new at a reasonable price with a warranty there is probably not much benefit in going down the used route even if they are a top brand.


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    #11
    air
    Registered Users Posts: 2,822 ✭✭✭air


    Panels will last longer in Ireland than in many locations.
    Wet is not an issue whatsoever but our narrow temperature range is.
    It's the mechanical effects of thermal cycling that have the biggest impact on lifetime by far.


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    #12
    u2me
    Registered Users Posts: 100 ✭✭u2me


    I thought the primary concerns might be water ingress and cell micro-fractures. I would have thought junction boxes might be susceptible to water ingress over time in Irish weather.

    I have been reviewing product warranty, performance warranty, and % power after 25 years of panels and now trying to decide based on a cost-effective combination of reliability and price and I have it down to two maybe three which I am considering.

    There is not a great deal of difference between them from what I can see so will probably base the final decision on the build quality and any available manufacturer and product reviews I can find.


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    #13
    air
    Registered Users Posts: 2,822 ✭✭✭air


    I've never heard of water ingress being an issue anywhere.
    Cell micro fractures and cell to ribbon fractures would be an issue but those are down to the thermal cycling, which we have much less of than other climates.

    I've seen discoloured back sheets but those are generally dealt with via warranty, de-lamination is rare.

    I'd go with the cheapest per watt to be honest, there are next to no poor panels on the market now as far as I can tell.


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    #14
    u2me
    Registered Users Posts: 100 ✭✭u2me


    ok thanks, good to know. Due to budget restraints :) I have not much choice but to go with the cheapest best quality one I can get. I have two or three brands now with 10-20 year warranty that are competitively priced so I can shop around and see where the best value is.


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