Different orientations !

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  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: Different orientations !

    BB if would my in my place and you will have space for 2 separate inverters . what will you do ??? install 2 SB4000 or 36 enphase ?
    thankyou
  • BB.BB. Super Moderators, Administrators Posts: 29,967 admin
    Re: Different orientations !

    I am not in the solar business, so I have no inside information.

    I am not thrilled with 36 inverters installed under hot panels on a roof. I would worry about the inverters lasting the 25-40 year life expected for solar panels.

    Replacing an inverter every ten to fifteen years on the wall of garage seems easier.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: Different orientations !

    I want to ask same question again :)
    So now I have 36 canadian solar
    18 on south
    18 on north
    PV watts shows me annual 11690KW production
    But i want to install only one SB7000US for 36 panels
    I know best way is to installl one 4ooo for north and one 4ooo for south but i have no space
    So if i will install one 7ooo how much approximate will i loos production
    thank you
  • mike95490mike95490 Solar Expert Posts: 8,563 ✭✭✭✭✭
    Re: Different orientations !

    That's a tough question with no easy answer. The different oiriented panels will drive the single MPPT nuts, and there is no way to predict what the result will be.

    I'd say just skip the panels with the low yield, and harvest the cream.
    Powerfab top of pole PV mount | 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 ,

  • BB.BB. Super Moderators, Administrators Posts: 29,967 admin
    Re: Different orientations !

    Solar Guppy's testing/experience says to install two different inverters for arrays that face two different directions.

    With one inverter the inverter will have problems finding the "true" Max Power point for the arrays (there may be two or three local "peaks" in the I*V curve due to the two different operating temperatures). Inverter MPPT software is not designed to find and track the actual peak--So it may lock on any of the peaks and not be on Vmp*Imp for the array.

    And, most likely Vmp*Imp of a "blended array" will not give you the same power has dedicated arrays to each panel set orientation with their different Vmp*Imp values due to Panel Temperature and Light conditions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: Different orientations !

    OK i Installed one system same as this ....18 canadian on west 18 canadian on east . and i connected on 1 7ooous .... and it s producing 38kw a day .....it means with one inverter or with two inverter production difference is not much
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Different orientations !

    Well by my math, its 13% less when compared to my system.

    I have 14kw with 3 inverters, yesterday did 75kwh. Your system did 38kwh with 8.1kw of PV

    75000 / 14000 = 5.357
    38000 / 8100 = 4.69

    Or about 13% less on your system to my system. Both are mixed orientations, we are pretty similar in latitude.

    You can't use PV watts to compute mixed orientations on single vs multi arrays and PV watts is an average over years of data not a single day.
  • BatikikikBatikikik Solar Expert Posts: 141 ✭✭✭✭✭
    Re: Different orientations !

    Solar Guppy , you cannot do calculation like that .
    Because maybe your panels PTC rating is not the same as my panels PTC rating .
    Or derate factor ....
    what kind of panels do you have on that system ??
    And what is the DC to AC derate factor ???
    what is the tilt angle and what is the orientation ?
    Thing all you have to keep in mind .... that is why 13% difference I dont belive in that nomber , but from another hand I respect your opinion ;)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Different orientations !

    Batikikik,

    I think what everyone is trying to explain is that there will definitely be a loss in your proposed configuration, but that the amount of that loss is not predictable. It may not even be consistent.

    As the inverter runs through its MPPT function it will find an inconsistent and wrong Vmp*Imp from the two strings and will pick some power point which is not optimum. Exactly what they point will be for any given sampling or averaged over time no one can be certain of.
  • Ralph DayRalph Day Solar Expert Posts: 898 ✭✭✭✭
    Re: Different orientations !

    Aurora One grid tied inverters have two string inputs for just this eventuality. You can have two differently oriented strings used by the same inverter and each is treated separately. I have no experience with them, but went with Enphase instead.

    Ralph
  • mr.radonmr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    Re: Different orientations !

    Some people say Enphase is not as good as a conventional inverter. I did a study for college on this topic. (continuing education classes) I did a DFMA, QFD and FMEA on mirco inverters verses the traditional inverter system.
    For failure, system complexity, installation ease, reliability, trouble shooting, failure detection, panel configuration, and a few more metrics the micro inverter model won out. The issue arises when cost is compared. Are you getting a good return for the extra cost. That is the case by case choice people have to make.
    In the case given here I would not be trying to hook up a traditional inverter. Just go with the Enphase inverters, problem solved.

    I'll have to dig out the report and post it. Kinda like a white paper.

    DFMA (design for manufacturability)
    QFD (Quality Function Deployement)
    FMEA (Failure Mode and Effects Analysis)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Different orientations !
    mr.radon wrote: »
    Some people say Enphase is not as good as a conventional inverter. I did a study for college on this topic. (continuing education classes) I did a DFMA, QFD and FMEA on mirco inverters verses the traditional inverter system.
    For failure, system complexity, installation ease, reliability, trouble shooting, failure detection, panel configuration, and a few more metrics the micro inverter model won out. The issue arises when cost is compared. Are you getting a good return for the extra cost. That is the case by case choice people have to make.
    In the case given here I would not be trying to hook up a traditional inverter. Just go with the Enphase inverters, problem solved.

    I'll have to dig out the report and post it. Kinda like a white paper.

    DFMA (design for manufacturability)
    QFD (Quality Function Deployement)
    FMEA (Failure Mode and Effects Analysis)

    That would be an interesting read. Especially as Enphase hasn't been around long enough for any real-world reliability data to be gathered (in comparison to other units). Some of the other conclusions you've drawn are debatable as well. Particularly "system complexity", "trouble shooting", "failure detection" - since a comparably sized Enphase system has more parts than a 6kW standard grid tie - like 30 times the number of inverters.

    The micro-inverters do score when the problems are panel shading or when "ease of installation" is an issue. A professional installer shouldn't care, but the DIYer would prefer the simplicity of the Enphase. So, regrettably, would the illegal "guerrilla installer" who isn't going to get permits or consult with the utility or follow NEC rules or even use proper circuit protection. That's one thing I worry about with the Enphase; it makes it too easy for someone to do something very, very wrong.
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Different orientations !
    Particularly "system complexity", "trouble shooting", "failure detection" - since a comparably sized Enphase system has more parts than a 6kW standard grid tie - like 30 times the number of inverters.
    The only drawback micro-inverters have in your list above compared to central inverters is system complexity with the additional parts. Troubleshooting and failure detection are much easier with micro-inverters as any issue is isolated to a single panel/inverter and the monitoring system will highlight that unit for you. It's as simple as looking at the weekly production numbers for each unit - if one is significantly lower than the rest - you've found the problem and know exactly where to look.

    In a central array, you might notice that the entire array is performing 10-20% under normal - but where do you start looking for the failed panel? With micro-inverters you have every other unit to use for comparison at any point in time.
    That's one thing I worry about with the Enphase; it makes it too easy for someone to do something very, very wrong.
    Like how, exactly? IMO, high voltage DC is a bigger threat to safety than micro-inverters.
  • mike95490mike95490 Solar Expert Posts: 8,563 ✭✭✭✭✭
    Re: Different orientations !
    ...... That's one thing I worry about with the Enphase; it makes it too easy for someone to do something very, very wrong.

    It brings the possibility of using the "simple" "easy" inverters to get wired to an extenstion cord and just plugged into the closest outlet. Next month, another panel goes in, and another cord. Pretty soon outlets are full, and cube taps get installed. ...

    I guess if someone swaps hot and neutral leads, the inverter wont fire up at all.

    Then you have the envoy for data collection, and the internet needed to get the data un-encrypted so you can read it. (and the annual monitor fees)
    Powerfab top of pole PV mount | 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 ,

  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Different orientations !
    mike90045 wrote: »
    It brings the possibility of using the "simple" "easy" inverters to get wired to an extenstion cord and just plugged into the closest outlet. Next month, another panel goes in, and another cord. Pretty soon outlets are full, and cube taps get installed. ...
    You're assuming that people have 240V outlets laying around? In which case that doesn't preclude you from using a regular inverter.
    mike90045 wrote: »
    Then you have the envoy for data collection, and the internet needed to get the data un-encrypted so you can read it. (and the annual monitor fees)
    True - though people are working on that.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Different orientations !
    drees wrote: »
    Like how, exactly? IMO, high voltage DC is a bigger threat to safety than micro-inverters.

    That pretty much proves my point.
    Micro-inverters are "low Voltage" and "low Wattage" so they're safe, right?
    So someone thinks they can install it on their own, no worries. No permits either. No inspections. No following NEC. One little panel won't hurt. Makes the electric bill go down. So two would be better. Or four. Next thing you know they've Jerry-rigged thousands of Watts on to an over-loaded panel and burn the house down or electrocute themselves.

    Sometimes it's a good idea to be afraid of electricity.
    Often we see posts here that make me want to respond with "If you don't know any more about electricity than that, you shouldn't be messing with it."
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Different orientations !
    Sometimes it's a good idea to be afraid of electricity.

    Or at least to behave as though you are. I'm not afraid of electricity, but I always act like I am. That's how electricians get to be old electricians.

    "There are old pilots, and there are bold pilots - but there are no old bold pilots."
  • mr.radonmr.radon Solar Expert Posts: 158 ✭✭✭✭✭
    Re: Different orientations !

    This was the mentality before states began to allow homeowners to do their own electrical work and to allow hardware stores to sell electrical supplies. Electricains said homeowners would die and houses would burn down every day. As it turned out people are scared enough of AC power to stay away if they are clueless. However, some people will make mistakes.
    WA lets any homeowner do anything to their house as long as they own the property. You are required to pull permits but no one checks for a permit when you buy supplies. This is the way it should be. If you have an objection to Enphase then you would also have an objection to selling circuit breakers, outlets, switches, lighting fixtures at hardware stores.
    I like the way it is set up. Obviously those that make their living as an electrical contractor have LOTS of issues with this freedom.
    The Enphase system is not simple, the average homeowners would not have an easy time figuring out how to install this system.
    That pretty much proves my point.
    Micro-inverters are "low Voltage" and "low Wattage" so they're safe, right?
    So someone thinks they can install it on their own, no worries. No permits either. No inspections. No following NEC. One little panel won't hurt. Makes the electric bill go down. So two would be better. Or four. Next thing you know they've Jerry-rigged thousands of Watts on to an over-loaded panel and burn the house down or electrocute themselves.

    Sometimes it's a good idea to be afraid of electricity.
    Often we see posts here that make me want to respond with "If you don't know any more about electricity than that, you shouldn't be messing with it."
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Different orientations !
    mr.radon wrote: »
    This was the mentality before states began to allow homeowners to do their own electrical work and to allow hardware stores to sell electrical supplies. Electricains said homeowners would die and houses would burn down every day. As it turned out people are scared enough of AC power to stay away if they are clueless. However, some people will make mistakes.
    WA lets any homeowner do anything to their house as long as they own the property. You are required to pull permits but no one checks for a permit when you buy supplies. This is the way it should be. If you have an objection to Enphase then you would also have an objection to selling circuit breakers, outlets, switches, lighting fixtures at hardware stores.
    I like the way it is set up. Obviously those that make their living as an electrical contractor have LOTS of issues with this freedom.
    The Enphase system is not simple, the average homeowners would not have an easy time figuring out how to install this system.

    Gee, I wish I was young enough to know everything. :roll:

    The fact is a lot of homeowners do their own electrical work and it is perfectly safe. A lot of others do their own work and it is an abomination. There have been many cases of blown fuses/breakers, wire fires, house fires, electrical shock, and even death due to faulty installs. I'd like to say this is limited to unlicensed electricians, but that isn't true.

    Some of the things I've found over the years include wire-nut connections within walls, wires "secured" by being wedged under bent nails, wires tucked between hanging wire and heating vents, stove outlet installed in the floor under the stove, outlets "looped back" to a second breaker, and innumerable over-loaded circuits.

    I've been around for more than half a century and never recall a time when electrical goods weren't available to the general public. Folks used to have sense enough to know what they didn't know. That doesn't seem to be the case anymore.

    And some of those micro-inverters are 120 VAC (not Enphase) and can be "plugged in" to wall outlets for back-feeding. How safe is that? I'd be among the first to admit that a lot of the NEC is over-kill, but a lot more is darn good reasoning designed to keep people from getting killed.

    When someone finally does do a fatal guerrilla install the headlines will read "Solar Power Proven Dangerous". Don't think that they won't.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Different orientations !
    Batikikik wrote: »
    I want to ask same question again :)
    So now I have 36 canadian solar
    18 on south
    18 on north
    PV watts shows me annual 11690KW production
    But i want to install only one SB7000US for 36 panels
    I know best way is to installl one 4ooo for north and one 4ooo for south but i have no space
    So if i will install one 7ooo how much approximate will i loos production
    thank you

    I can provide a sample 'data point' for your consideration, WRT multiple orientations connected to just one inverter.

    My system is very similar to yours: I have 36 Astronergy 225 W panels (8.1 KW DC), connected as 4 strings of 9 panels each to an SMA Sunny Boy 7000 watt grid-tie inverter.

    In my case, 3 of the strings are with panels at 215° azimuth. The 4th string is at 285°. All panels are at 35° tilt. I'm at a Dallas area Lat. and Long.

    A diagram of the system is here, in the upper right corner: http://www.welserver.com/WEL0043/ .

    If all 36 panels were to be oriented at default 180° azimuth at 35° tilt, with one inverter, and if assuming a default DC to AC derating factor of 77% in a no-shade environment, PV Watts estimates annual output at 11,367 kWh.

    So in my case, having panels not aimed at perfect 180°, and mixed amongst 2 different orientations (215° and 285°), and still using only 1 inverter, I too have been interested to see how much the performance degradation will be.

    Here's a chart showing my actual solar PV efficiency (on a 30 day rolling average basis) for the past 4 months. It clearly shows degradation. My observation is PV efficiency has been about 73%, on average for the 4 months I've been so far measuring it so far. So I'm lower than the 77% PV Watts default assumption by about 4 percentage points.

    SolarPVefficiency.gif


    Here's another chart showing the same picture, this one showing actual monthly harvest (orange line) versus PV Watts estimate (at 77%) (green dashed line).

    MonthlyEnergyConsumption.gif


    My SB 7000's MPPT performance appears to be pretty solid, with little 'hunting' back and forth between multiple peak instantaneous peak power points. Here's a final chart showing yesterday's power output (cloudless day) on a 2 min. sample basis (blue line). You can see some 'hunting' occuring but it's minimal.

    InstantaneousSolarPower.gif


    My conclusions are three-fold:
    1. For multiple combination panel orientations using just one inverter, it's going to degrade performance.
    2. The amount of degradation may not be a large amount though, if the (single) inverter's MPPT capability can well handle the multiple orientations. In my case, it looks to be about 4 percentage points degradation, relative to PV Watts' default 77% PV efficiency assumption.
    3. The SMA Sunny Boy 7000 inverter is a strong performer in a multiple panel orientation enviironment.
    Hope this helps.

    Best regards,

    Bill
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Different orientations !
    a0128958 wrote: »
    My conclusions are three-fold:
    1. For multiple combination panel orientations using just one inverter, it's going to degrade performance.
    2. The amount of degradation may not be a large amount though, if the (single) inverter's MPPT capability can well handle the multiple orientations. In my case, it looks to be about 4 percentage points degradation, relative to PV Watts' default 77% PV efficiency assumption.
    3. The SMA Sunny Boy 7000 inverter is a strong performer in a multiple panel orientation enviironment.
    Just one comment on your analysis - your situation while similar in that you have multiple facets - your facets are "only" 90* apart compared to the 180* apart of the OP.

    I would expect that the further apart in in facets the arrays are in direction, the more drastic the reduction in production will be.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Different orientations !
    drees wrote: »
    ... I would expect that the further apart in in facets the arrays are in direction, the more drastic the reduction in production will be.

    Agreed. Now that you bring this up, I should have added a 4th point (as you wrote):

    4. The farther apart the 2 orientations are, the more dignificant the efficiency performance degradation will be.

    Thanks for adding this observation.

    Best regards,

    Bill
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭
    Re: Different orientations !

    Bill,

    He's not going to see things go completely miserable because Voc and Vtemp aren't going to vary too horribly much as long as the sun is ON the panels. And if the sun is on the other side of the array, it doesn't matter anyway -- they won't be making much power.

    The best way to look at all these things is to calculate the performance loss in dollar and compared to whatever it would take to "fix" it. More panels in bad orientations is often cheaper than more inverters AND more panels ...
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Different orientations !
    tallgirl wrote: »
    ... More panels in bad orientations is often cheaper than more inverters AND more panels ...

    Agreed.

    Best regards,

    Bill
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