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  • #16
    Originally posted by ImInPhxAZ View Post
    .... Conduit also introduces massive heat and resistance in the wires, so not using conduit will save you some %of energy too.........
    Them's some strange words pardner. Care to back them up with some facts ? In fact, I insist, or edit your post.

    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
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    • #17
      Originally posted by ImInPhxAZ View Post
      That's another plus for sunpower then, as their micros are 320w vs iq6+ being 290w. Imagine those 365 panels if facing anywhere 91 to 269 degrees will have a share of clipping that will eat up the price difference. So Trina vs sunpower. $676 for the brand and the guarantee (92% output @25yrs). That's up to you. I hear their software is top notch but I haven't used it...
      ​​​​​​
      To the degree such things may be important, I'd think the inverter max. output to panel STC output ratio would be the more significant parameter here rather than simply comparing output one micro against another and then saying the micro (by itself) with the larger output has an advantage.

      Instead, the higher the inverter to panel STC ratio, the less likely it is that clipping will occur.

      Ratios:
      S.P : 320/360 = 0.89
      LG : 290/365 = 0.79
      Trina : 290/300 = 0.97

      So, under that proposition, S.P. is not the winner of that race.

      However, that micro /STC ratio parameter probably ought not to be taken in isolation from other considerations, one such consideration being how likely the operating conditions will be to produce clipping, and then, how often such conditions are likely to occur.

      Assuming we believe spec sheet claims for now, one other thing to consider (of several) is really at least two things: how likely is a panel to get to its STC output, and if so, how much lost output from clipping is any such clipping likely to produce.

      As the OP states, DFW gets hot. Well, Under max. POA irradiance conditions, the panels siting on my brown concrete tile roof with about a 10+" standoff typically, in bright sun, get about 25 C.to 30 C. warmer than the ambient air temp. on the roof and about 30 C. to 35 C. warmer than the ground level ambient air temp. That Approx. 5 C. range in max. panel temp. is due to differences in winter to summer irradiance levels and variation in the wind, with some additional panel to panel variation from the wind's leading to trailing edge over the entire array.

      Using that approx. 35 C. amb. to panel temp. diff. and a fixed 1 kW/m^2 POA irradiance, as air temps. increase, under the same conditions, and in a side/side comparison, the LG will clip at lower amb. temp. and thus a lower panel temp. than the S.P., with the Trina the last to clip (that is, at the highest ambient temp.). The same will hold true as the POA irradiance levels drop below 1kW/m^2, but the panel to amb. temp. will also decrease in a way that's approx. proportional to the POA irradiance change.

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      • #18
        Can you DYI...------------------------ kits are a great value and you get a rate of return much faster. It's a waste of time and money to have a 10 year rate of return...
        Last edited by Mike90250; 05-14-2018, 12:55 AM. Reason: vendor neutral

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        • #19
          Originally posted by Six4KilowWatt View Post
          Can you DYI...Anapode Microinverter kits are a great value and you get a rate of return much faster. It's a waste of time and money to have a 10 year rate of return...
          I would LOVE to DIY this.... BUT... we have a two story house with quite a good slope to it and a 25+ft straight drop down on the area where the panels are going. I tried to get up on the roof one time and couldn't even get a few feet up without slipping in good tennis shoes with grip. Scary stuff to me. If we were on a single story with less slope, I would 100% DIY though. We do every other major remodel ourselves. I've built houses with Habitat for Humanity and at our church, putting up decking without a harness, and that wasn't a problem (until someone tried to remove my footing board from underneath while I was using it!), but ours is just too high and steep for me. It's the only thing I really am not happy about with our plans. Oh well... yes, the 12yr break even sucks, but we're not necessarily doing this just for quick financial benefits. And the way I look at it, the tax credit and CoOp rebate cover the cost for install.

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          • #20
            For the price difference that OP mentioned, and since he asked for opinions, I shared mine.
            I don't own any sunpower stock.

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            • #21
              Originally posted by glocklt4 View Post

              I would LOVE to DIY this.... BUT... we have a two story house with quite a good slope to it and a 25+ft straight drop down on the area where the panels are going. I tried to get up on the roof one time and couldn't even get a few feet up without slipping in good tennis shoes with grip. Scary stuff to me. If we were on a single story with less slope, I would 100% DIY though. We do every other major remodel ourselves. I've built houses with Habitat for Humanity and at our church, putting up decking without a harness, and that wasn't a problem (until someone tried to remove my footing board from underneath while I was using it!), but ours is just too high and steep for me. It's the only thing I really am not happy about with our plans. Oh well... yes, the 12yr break even sucks, but we're not necessarily doing this just for quick financial benefits. And the way I look at it, the tax credit and CoOp rebate cover the cost for install.
              While you're writing about access, think about some things.

              - How will you or service personnel get to the array, and particularly panels within, say a 4 X 4 array for maint. ? One of the big drawbacks of micros is that with a lot more electronics - 1 inverter per panel (16 ?) in a harsh environment instead of 1 inverter in a safe(r) environment in a garage that's easily accessible, the probability of failures and requiring service is higher as will the need to have access to the roof. Ever think about how you or service folks will get at a micro in the middle of a 4 X 4 array, or at all for that matter ?
              - Dirty little secret installers somehow miss: Panels need cleaning. Not much - probably about 1 gal./panel ~ 1X/month or so when it doesn't rain, and probably not much mechanical brushing beyond may 1X/yr. or so, but it will need some.

              Also important: get your roof at the array location inspected and serviced. Repairs under an array are involved and expensive with the array reinstall likely never done as well as the original.

              One of the common shortcomings in rooftop arrays is the lack of planning or considerations about what happens after install when maint. is required. People don't plan to fail, they fail to plan. Think ahead, what can likely go south and plan for it.

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              • #22
                Originally posted by J.P.M. View Post

                While you're writing about access, think about some things.

                - How will you or service personnel get to the array, and particularly panels within, say a 4 X 4 array for maint. ? One of the big drawbacks of micros is that with a lot more electronics - 1 inverter per panel (16 ?) in a harsh environment instead of 1 inverter in a safe(r) environment in a garage that's easily accessible, the probability of failures and requiring service is higher as will the need to have access to the roof. Ever think about how you or service folks will get at a micro in the middle of a 4 X 4 array, or at all for that matter ?
                - Dirty little secret installers somehow miss: Panels need cleaning. Not much - probably about 1 gal./panel ~ 1X/month or so when it doesn't rain, and probably not much mechanical brushing beyond may 1X/yr. or so, but it will need some.

                Also important: get your roof at the array location inspected and serviced. Repairs under an array are involved and expensive with the array reinstall likely never done as well as the original.

                One of the common shortcomings in rooftop arrays is the lack of planning or considerations about what happens after install when maint. is required. People don't plan to fail, they fail to plan. Think ahead, what can likely go south and plan for it.
                Thanks for the additional comments. The plan is likely a 2x5 + 1x6 array layout. Since warranty (parts and labor) is included for 25yrs from SunPower on both the panels and inverters, I have not considered much about the cost of replacing inverters if one were to burn out. I seriously doubt we will be in this house after 25yrs so it is really not that big of a concern (though, maybe it should be). I will ask about MTBF rates with the SunPower inverters and the cost to have something like that replaced outside of warranty just to see. I do agree that a cooler garage with a single inverter is better from that stand point, but I think micro-inverters are the way to go in the long run regardless.

                I can reach the panels from the ground with water with my power washer and no nozzle attached to the end for cleaning, but we usually get rain once a month or so minimum anyway. July/August would be the only month we don't possibly so I'll monitor output from the system then. I thought I had read that there really wasn't much need for mechanical cleaning of panels if they are at a good enough slope and you receive heavy rain periodically, but everything does get dirty outside eventually. I'll ask the installers what that runs if/when needed. I have a tall ladder that would probably get me up high enough to brush them off with a squeegee after a wash.

                We just had a new roof put in 2 years ago, so we're good there.
                Last edited by glocklt4; 05-14-2018, 04:13 PM.

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                • #23
                  Originally posted by glocklt4 View Post

                  Thanks for the additional comments. The plan is likely a 2x5 + 1x6 array layout. Since warranty (parts and labor) is included for 25yrs from SunPower on both the panels and inverters, I have not considered much about the cost of replacing inverters if one were to burn out. I seriously doubt we will be in this house after 25yrs so it is really not that big of a concern (though, maybe it should be). I will ask about MTBF rates with the SunPower inverters and the cost to have something like that replaced outside of warranty just to see. I do agree that a cooler garage with a single inverter is better from that stand point, but I think micro-inverters are the way to go in the long run regardless.

                  I can reach the panels from the ground with water with my power washer and no nozzle attached to the end for cleaning, but we usually get rain once a month or so minimum anyway. July/August would be the only month we don't possibly so I'll monitor output from the system then. I thought I had read that there really wasn't much need for mechanical cleaning of panels if they are at a good enough slope and you receive heavy rain periodically, but everything does get dirty outside eventually. I'll ask the installers what that runs if/when needed. I have a tall ladder that would probably get me up high enough to brush them off with a squeegee after a wash.

                  We just had a new roof put in 2 years ago, so we're good there.
                  You are welcome. Understood. It's not so much the cost of replacement as the potential problems from getting at them and getting it done right.

                  Paying for panel cleaning is a waste of money. Just hit them 1X/month of so w/H2O from a hose, but best do it before direct sun, early in the A.M. to avoid thermally shocking the glazing.

                  My array's performance declines ~ 1% per week from dust/dirt, etc. accumulation if it doesn't rain, but most every situation is probably slightly different.
                  After ~~ 8-10 weeks or so of no rain, the performance deterioration of my array from fouling (dirt) seems to level off some in a hard to quantify way.

                  I cannot measure a difference in cleaning with soap, or no soap, with or without brushing. Such brushing with a soft cloth, while sometimes needed for something like a big owl skrock, doesn't seem to restore more performance than does simple hosing on a semi regular basis.

                  Same goes for water spots from hard H2O. D.I. or distilled H2O rinse to get rid of water spots seems to produce no measureable improvement in performance that I can measure.

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