PVsyst offers a special tool for viewing and
optimising
the shed mounting (and also sun-shields). This is implemented in
several places in the software:
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During the definition of the
project's parameters, the "Orientation" choice offers the
possibility of defining sheds or sun-shields. This will of course
take the corresponding mutual shadings into account during the
simulation process (on beam as well as diffuse component). |
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In "Tools" / "Tables and Graphs of Solar
parameters", you can define the geometry, optimise it with
the mouse, and view the mutual shading effects of your choice on an
Height/azimuth diagram. |
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In "Tools" / "Monthly Meteo Computations": you can
moreover have a quick meteo calculation for your site, and
immediately estimate the irradiation losses over the year. |
With these
tools, the mutual shading of sheds (or sun-shields) is performed
using a simple geometrical
computation, which gives the mutual shading fraction as a
function of the
Transverse Incidence Angle or "Profile angle" in the
shed orientation.
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This calculation is performed
assuming sheds of "infinite"
length (that is, it doesn't take the edge effects into
account). |
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The calculation may be performed
for irradiance, i.e. the
shading factor is the shaded area fraction of the full array
(depends only on the pitch and tilt angle). This also slightly
depends on the number of sheds as the first one is not shaded.
This is what we call the "linear" shading. |
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You can also estimate the
electrical effect of these
shadings. |
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Remember that the current of the
whole string (as seen from the inverter input) is limited to the
current of the weakest cell, i.e. the shaded one. Therefore we
suppose that the production of the bottom string becomes null
(regarding beam component) if the bottom row of cells is fully
shaded, and proportional to the shaded fraction of the cells
otherwise. This is what we call shading "according to module strings" in
the near shadings. |
In this option
this calculation requires the specification of the number of
strings in the transverse dimension of the shed, as well as the
size of one cell. The shading factor effect is shown as a function
of the
profile angle.
Please note that with thin film modules with "long" cells of
around 10 mm width, the cells should be placed in the transverse
dimension of the shed, so that only a little part of each cell is
shaded at a time.
The three parts of the shed tool: Geometrical design,
Shading
graph and Yearly yield graph,
are meant for a better understanding when
optimising a shed layout.
Please
carefully see the limitations when using sheds with
near shading scenes.
