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Optimum photovoltaic panel inclination

  1. Jul 11, 2011 #1


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    Does anyone know any good reading sources that help with the following calculations:

    1) find the optimum photovoltaic inclination from the horizontal
    2) find the radiation for this pv panel when you know what the global, direct and diffuse radiation is

  2. jcsd
  3. Jul 13, 2011 #2


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    Staff: Mentor

    I googled your term: optimum photovoltaic inclination, and got lots of good hits. Google is your friend...


  4. Jul 13, 2011 #3


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    What I meant to ask was are the calculations the same when you are installing in the southern hemisphere and thus the panels face north.

    Apologies for the confusion
  5. Jul 15, 2011 #4
    In order to determine the optimal inclination for PV panels, probably the easiest way to determine it is to use PV Watts tool which can be found at the following link: <http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/>. An easy rule of thumb is to incline the PV panels to match the latitude of the location where PV will be installed.

    For example, in NJ, the ideal inclination is 40.7 degrees, equivalent to the latitude. It should not matter whether you are in the northern or southern hemisphere as far as inclination is concerned so long as PV panels are facing the right orientation.

    To calculate the production of a solar system, you can use the following formula:

    (AC Rating of the system x Hours of Peak Sunlight x Design Factor x 365) / 1000.

    For example, 399.5kwDC system with 342.394kwAC will be calculated as follows:

    (342,393.60 x 4.3 x 85% x 365) / 1000 = 456,779 kwh.
  6. Jul 15, 2011 #5


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    1) The answer is somewhat dependent on your requirement.

    Yes tilt at latitude if the panel inclination angle must be fixed, *and* if the desired goal is specifically to maximize average yearly energy collection. However, if the goal is to maximize the minimum power output, which may be the case for a remote sensor powered by PV and the like, then the angle should be much higher to optimize collection for the winter sun (and also to aide in shedding snow or debris cover) at the cost of lost but unnecessary energy in the summer.

    Here for example is a PV powered stoplight (supposedly required only in the day) in Houston, Tx, latitude ~30N. I'd guess this panel is mounted 50-60 deg.

    If the panel angle can change, then through out the year the angle should be:

    [PLAIN]http://www.pvresources.com/images/location/tiltangle.png [Broken]

    2) See NREL's monthly/yearly data http://rredc.nrel.gov/solar/pubs/redbook/" [Broken]: fixed plate tilted at latitude - 6.5 kWh/M^2/day annual average, minimum 5.9, maximum 6.7. Two axis tracker - 8.9 kWh/M^2/day annual average (370W/M^2 daily average power).

    Note that if you have known shading figures (i.e. trees or other obstruction) for your location, for most existing panel designs shading won't translate linearly to reduced electric power output. That is, because of the way in which most all cell designs are wired together, a shading of (say) 25% of a panel's area might cause a reduction in electrical power output in 50% of the PV cells on the panel.
    Last edited by a moderator: May 5, 2017
  7. Jul 18, 2011 #6


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