Sunpower

Options
I can buy a 10k Sunpower grid tie. I only have 2K panels and only plan on 3k at max.
my voltages currently is..VoC-266, VdC-212
see attachment
'power loss may occur, but how much really?
Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Sunpower

    According to what I just saw on the link that inverter needs 230 Volts to start up. Nominal operational Voltage is 390.

    You say you have 212 VDC (Voc does not apply to start-up Voltage).

    What do you think will happen?
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    I think that there will be kinda late start up, maybe intermittent turn off during weather, and once I get a few more panels, add 74 Voc[ 60VdC] then all the numbers would work but at the lower corners of the data. My real concern is if the data sheets ARE correct? or not.? The data sheets say the efficiency drops off after 60% or so...also the Manuf. data sheet says it handles a power factor of 1.!
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    I have been under the impression that VOC started it, then the VDC determined MPPT function/shutdown, load volts
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Options
    Re: Sunpower

    Loaded panels do not produce Voc.
    The moment the inverter tries to start the panels are loaded and Voltage drops. If the Vmp of the array is not within the operating range of the inverter, it will not run.

    Voc is only important for not exceeding the maximum input Voltage of the inverter.
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    Ok so when the panels are producing voltage at dawn [low] the panel array/ inverter is loaded already/immediately. No room for, or application for ,VOC.
    Furthur misunderstanding ...my grid does not vary by more than 3v@120. So I always read that the 240v AC range of function was 211-230 VDC@240VAC and MPPT @230VDC. It is arranged differently in different white papers. It only has one MPPT and the planned remainder of my array[5 more panels] would be in the shade , about 2-3 panels for a few hours in the evening. It IS grossly over sized, my whole house load is only 3000 Unbalanced max! This is an opportunity for me to land a decent Grid tie for up 3600W with solar insulnation[sp]? hopefully be 13-15 panels 230W24V....[I got a little credit, only 500.00 and I can't combine funding sources...so I may actually be able to get a genuine LU certified applicable Grid Interactive inverter I can let melt into the utilityies Outside and not in my wash room!
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Sunpower
    Scalene wrote: »
    Ok so when the panels are producing voltage at dawn [low] the panel array/ inverter is loaded already/immediately. No room for, or application for ,VOC ...

    At pre-dawn, (no sunlight striking the PVs) the Vocs for the day are usually the highest. As coot - Marc stated, Voc is just that Voltage - Open Circuit. This means that there IS NO LOAD on the PVs.

    PV modules are really current sources, not voltage sources. For PVs, there is no real power avail under Voc conditions, and any attempt to use the vanishingly small amount of current that the PVs MIGHT produce at pre-dawn, would cause the voltage to crash to a low value.

    When the sun is striking the PVs, the cell temperatures fall, causing the available power to increase, and the string voltage to fall.

    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    Thank you, I am not buying the 10K inverter, currently trying to buy a SB3000US, really good by the web design tool for my purposes/plans..
    Question, with these Chinese inverters the voltage remains constant 29-31...
    Will the voltage vary some with the series setup, in relation to demand of the load? or available PV power?
    Also with a series set up, does the array come to full power earlier at 8A@ 230V than like 60A@24V?
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • BB.
    BB. Super Moderators, Administrators Posts: 33,469 admin
    Options
    Re: Sunpower

    More or less, under practical/useful power from your solar array, Vmp-array will vary with respect to cell temperature. The MPPT software in the GT inverter will attempt to maximize Pmax=Vmax*Imax by "sweeping" the current and measuring the resulting current--Looking for Pmax.

    Vmax will vary a little bit at different load points, but, for a first approximation, Vmp is proportional to cell temperature (hot day, full sun high cell temperature and depressed Vmp-array). Cold day with clouds passing in front of sun, cold cells and high(er) Vmp-array.

    I am not sure I understand this question:
    Also with a series set up, does the array come to full power earlier at 8A@ 230V than like 60A@24V?

    If you are comparing two different GT inverters (a 230 VDC vs a 24 VDC)--There is no real difference in panel/GT inverter behaviour (early morning, noon, evening, etc.). The only difference is with lots of cells/panels in series, any shading along a 10 panel string will affect Vmp-array (and Imp-array will remain relatively constant). With a bunch of 24 volt panels in parallel, shading one panel will not affect Vmp-array (it will however, drop Imp-array).

    If that was your question....

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    I will have to research Imp/parallel vs. Vmp series applied significance, I think there is enlightenment there! [of the academic/scholastic variety]
    My question is[happy new year] In the morning with 30v 60a maximum the panels reach max output only for a short while @ midday, reaching max volts first then amps till noon and after.
    morning 24v 2a-4a-6a......noon < Parallell
    series morning 8a 20v-40v-60v till noon then decreasing
    I imagine it would be a power curve a little less humped with full power being at 8A and 220V~ than 30V 50A~
    the volts for series- rising sooner than the amps for parallel.
    and amps for series- only needing 8 vs. the 30v for parallel.
    on two graphs...
    1. y=watts x=time for series
    2 y=watts x=time for parallel
    continuing graphing for volts/time series parallel & amps /time series/parallel
    do the volts in series behave like amps in parallel?
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • BB.
    BB. Super Moderators, Administrators Posts: 33,469 admin
    Options
    Re: Sunpower
    Scalene wrote: »
    I will have to research Imp/parallel vs. Vmp series applied significance, I think there is enlightenment there! [of the academic/scholastic variety]
    My question is[happy new year] In the morning with 30v 60a maximum the panels reach max output only for a short while @ midday, reaching max volts first then amps till noon and after.
    morning 24v 2a-4a-6a......noon < Parallell
    series morning 8a 20v-40v-60v till noon then decreasing
    I imagine it would be a power curve a little less humped with full power being at 8A and 220V~ than 30V 50A~
    the volts for series- rising sooner than the amps for parallel.
    and amps for series- only needing 8 vs. the 30v for parallel.
    on two graphs...
    1. y=watts x=time for series
    2 y=watts x=time for parallel
    continuing graphing for volts/time series parallel & amps /time series/parallel
    do the volts in series behave like amps in parallel?
    For day to day typical operation with a MPPT input type controller (GT solar, Solar charger, etc.), it does not matter.

    To get "useful" amount of power from the array, it has to reach Vmp-array for the controller (and supply XX watts to "turn on" the MPPT controller and run the local electronics/switching power supply). If Vmp-array is below the name plate value (no direct sun on panel), there is not enough current to produce hardly any power (usually the MPPT controller pulls more power than the array can supply). My GT inverter pulls almost 50 watts before it generates 1 watt of power to the grid.

    So if you have Vmp-array = 300 volts and 10 amps or 30 volts and 100 amps, until the array is at 300/30 volts, nothing much is going to happen with the MPPT device until there is enough "useful current" (call it 0.2 amps at 300 volts or 2.0 amps at 30 volts).

    Obviously from a wiring point of view, 10 amps at 300 volts is easier to wire for than 100 amps at 30 volts (plus 10 combiner box circuit breakers/fuses--one per panel).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Sunpower

    Scalene,

    Believe that you are trying much too hard to make the production of power from PV arrays far too difficult and complex.

    PV modules are essentially imperfect Current Sources. Weather there are 10 PVs or one per "string" the Pmax curve is still essentially the same shape (disregarding for now, any voltage requirement of a specific inverter or Charge Controller).

    Having higher string voltage brings NO benefit in early power production, compared to that same number of PVs in parallel (and therefore a lower voltage -- PVs are current sources (essentially). Voc is the voltage with no load on the PVs, and by definition produces no power.

    Am not certain that this is of any help, but just an attempt. FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Scalene
    Scalene Solar Expert Posts: 25
    Options
    Re: Sunpower

    I just thought that there may be a difference between Voc Vmp of the paralell 37-30 = full watts and Voc /Vmp of the array series 266 -? = full watts.
    Probobly over time the full power of the array delineates; but might there be a sizing way to utilize a differential if it existed[ theory?] Or is this like the pencil line width in geometry class?hahahaha?!
    because it is pretty fixed at 30Vdc for my 24v system, does series vary more? 0 power at open circuit, full power at Vdc, does the Vdc remain 30v at sereies math, so just multiply number of panels by 30Vdc[the 24v standard?] or does the GT manage it differently. There is 7v differential[voc vs.vdc] in a 24v parallel system and a 56v differential in a 8 panel series system. A measure of panel performance is -power at volt&temp- graphs I have seen. The distribution of power over a range of volts.
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • BB.
    BB. Super Moderators, Administrators Posts: 33,469 admin
    Options
    Re: Sunpower

    Power = Voltage * Current

    Voc= Voltage open circuit (i.e., no power flowing at all).

    Vmp= voltage at "optimum" output current (Vmp varies a bit with temperature, Imp varies with the amount of direct sunlight).

    For a 24 volt battery bank, you need around 30-31 volts at the battery for full/fast charging. With temperature, voltage drop of wiring, you need around VMp-array minimum of 35 volts.

    With a PWM charge controller, you need Vmp-array in the range of 35 volts to 38 volts or so for "optimum" power transfer through the PWM controller.

    For a MPPT controller it can have very close to optimum energy transfer above Vmp-array 35 volts (upwards of 100 Volt Vmp will work OK with larger MPPT controllers from name brand companies).

    In your case, if you are using Vmp~30 volt panels and a 24 volt battery bank, you really need to put two panels in series for Vmp-array~60 volts. And you should really have a MPPT type solar charge controller for efficient energy transfer (a PWM controller will cost you ~40% of a 60 volt Vmp array output wattage into a 24 volt battery bank).

    If you have a long wire run from the array to the charge controller/battery bank, then you may want to look at 3x panels in series for a 90 Volt Vmp array.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset