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  • J.P.M.
    replied
    Originally posted by Ho jo View Post
    Looking deeper for the same yearly production the 150° degree array would need to be 410 watts.
    My question is being 30° off from solar noon
    How much would the peak amps drop from the 26
    That I see now from 400 watts at 180°
    Is there anything sacred about the array orientations ? Depending on the orientation flexibility of the array(s), I might consider changing the array'(s) design azimuth and tilt to get the best match with the batteries and/or other considerations. Use the PVWatts hourly output option to see if/how output to battery charging requirements can be optimized for your application and site.

    None of this is rocket science and given the resource variability and unpredictability, it's probably not worth getting in a dither about a few degrees either way. Still, precision and a better assessment of resource availability being so easy to come by, getting a better guess is a lot easier, faster and cheaper than it once was to the point of being a no brainer.

    I'm don't understand your question ("How much would the peak amps drop from the 26" ).

    To your question, the current output of a silicon solar device (a PV panel) is about directly proportional to the irradiance on the array.

    The array irradiance is a somewhat complicated function of the angle of incidence of that irradiance on the array. So, and to a first approx., if irradiance drops because the angle the sun makes with the panel decreases, the current will drop approximately proportionately as the cosine of that angle of incidence (the AOI).

    There are any number of texts and net sources that will explain an/or calc. the angle of incidence on a surface of any orientation and at any location. I'd suggest that because it's so easy to do, putting it all on a spreadsheet is better than rules of thumb or less from those not on your site.

    NOMB, but if I was dealing with relatively small arrays of ~ 3 m^2 ea., I'd consider putting them on carts ballasted with the batteries and panels with adjustable racking and change orientations with the seasons or more often as necessary for real flexibility until I figured out the best orientation for the application. I did that once w/ ~ 5.5 m^2 solar thermal panels (but no batteries).

    Take what you want of the above. Scrap the rest.

    Leave a comment:


  • Ho jo
    replied
    Looking deeper for the same yearly production the 150° degree array would need to be 410 watts.
    My question is being 30° off from solar noon
    How much would the peak amps drop from the 26
    That I see now from 400 watts at 180°

    Leave a comment:


  • Ho jo
    replied
    @jpm At latitude running one array of 800 watts set at 180°
    compared to 1 array at 150° and another at 210°
    I would have to increase to 840 watts ~5℅
    420 watts on each array for the same annual production.
    Seems the added cost of racking and wiring
    ​​​​​​Might tip the scale vs cost of more frequent battery replacement And generator run time.
    Or Replacement.
    I have Lead Acid and their need for longer hours of charging.
    Last edited by Ho jo; 01-29-2020, 05:46 PM.

    Leave a comment:


  • J.P.M.
    replied
    If you want more production hours during a day or over a year, somewhat symmetric E-W orientations of 2 or more arrays will do that.

    However, to maximize annual output per m^2 of panel, which is usually linked to PV system cost effectiveness, there will usually to almost always be one orientation per site that will give you that - meaning more than one array orientation of the same panel area as one optimally oriented array will yield less production over a year's time.

    Virtual tracking arrays will usually to almost always require larger panel areas than a single array oriented for max. annual output. That means more panels and ancillary equipment for the same annual production for virtual tracking.

    Do this: Use PVWatts to see how much panel area is required for 10,000 kWh/yr. for your site for an optimally oriented array. Split the panel area in half and see if you can get the same production from 2 such arrays at any orientations.

    Virtual tracking may have some advantages for arrays that charge battery banks however.

    Leave a comment:


  • bcroe
    replied
    Originally posted by Ho jo View Post
    @bcroe I've been running numbers on pv watts and it seems
    that for 4 months of summer setting at 150 ~ SE. Gives me more daily production. We
    have frequent clouds and rain summer afternoons. so maybe thats why?
    Similar things happen here, often the best time to collect energy is before noon. That
    may be your best orientation, for a DC:AC ratio near one. I however want to double
    collection under the so frequent clouds, so my DC:AC exceeds 2. To protect my inverters
    and lengthen my useful sun day, the extra panels are oriented E and W to flatten out
    peak power under good sun. Bruce Roe

    Leave a comment:


  • Ho jo
    replied
    @bcroe I've been running numbers on pv watts and it seems that for 4 months of summer setting at 150
    ~ SE. Gives me more daily production. We have frequent clouds and rain summer afternoons.
    so maybe thats why?

    Leave a comment:


  • bcroe
    replied
    You will need to model what is best for you. The theme here at 42 deg Lat is to
    double up panels to make a lot more KWH under our ever present clouds. Having
    done that, the panels are E and W to give a long productive day instead of just
    going into big clipping, under good sun. If clouds are not common for you, a straight
    south orientation (with fewer panels) will get the most KWH per panel.

    A common event here is good sun in the earlier AM, then clouding over towards noon.
    I have the advantage of utilizing good sun to the max at any time it occurs.

    Another possible need, is to have as along a battery charging day as possible.
    Bruce Roe

    Leave a comment:


  • Ho jo
    replied
    @bcroe IIRC correctly you have spent many hours testing different pv angles.
    Winter solstice here is 31°.
    sunrise is at 120° azimuth.
    ​​​​​​​with such low angles and narrow sun path.
    In your opinion is there any advantage to aim other than due south?

    Leave a comment:


  • bcroe
    replied
    Originally posted by littleharbor
    Funny, the sun rises well north of 90 degrees, East, in my neck of the woods on the
    first day of summer the sun needs to get pretty high before it hits my, due South, fixed array. Way up north I
    would guess a dual axis tracker would work great to chase the sun around the sky in the summer
    It sets to the North as well. This is part of why an array facing East and another array facing West can
    collectively keep inverters, etc busy for long hours. Same applies when the sun rises and sets so far
    South half a year later. Bruce Roe

    Leave a comment:


  • littleharbor
    replied
    I'm no expert here but I would think something in the 130 to140 degree Azimuth would work.
    Funny, the sun rises well north of 90 degrees, East, in my neck of the woods on he first day of summer the sun needs to get pretty high before it hits my, due South, fixed array. Way up north I would guess a dual axis tracker would work great to chase the sun around the sky in the summer
    Last edited by littleharbor; 11-08-2019, 12:41 PM.

    Leave a comment:


  • Ho jo
    replied
    @littleharbor Just to be clear in Dec sun rise is 120° what degree setting ese would you recommend?
    ​​
    Last edited by Ho jo; 11-07-2019, 08:45 PM.

    Leave a comment:


  • littleharbor
    replied
    I'd guess that you would be better off aiming ESE and elevating the panel 15 degrees more than your latitude.
    Last edited by littleharbor; 11-07-2019, 05:40 PM.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by Ho jo View Post
    As I understand it virtual tracking the sun in summer.
    gains longer production.

    ​​​​​much less production in winter than summer.

    I use 2 systems 1 380 mppt array set due south.
    And 1 400 watt array on pwm.
    ​​​​
    In the winter mornings during bulk would I benefit by aiming the 400 watt array sse?




    If that 400w array was going through a MPPT CC then yes. Since it is going through a PWM CC you are already losing about 33% of the total panel wattage so the increase from the aligning the array to the sun would be minimal.

    Leave a comment:


  • Ho jo
    started a topic Virtual tracking

    Virtual tracking

    As I understand it virtual tracking the sun in summer.
    gains longer production.

    ​​​​​much less production in winter than summer.

    I use 2 systems 1 380 mppt array set due south.
    And 1 400 watt array on pwm.
    ​​​​
    In the winter mornings during bulk would I benefit by aiming the 400 watt array sse?





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