Atec Solmetric SunEye 210, Руководство пользователя

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4-2
Solar Access and Interpretation of Data
Shading
The sun’s elevation is the angle formed between the observer, the horizon, and the sun above the
horizon. The azimuth is the angle created by the sun’s deviation from true north in relation to the
observer. The sun follows a predictable path through the sky based on the time-of-day, day-of-
year, and latitude of the observer. Therefore, the elevation and azimuth angle of the sun can be
calculated for any time, date, and latitude. The collection of sun trajectories for the entire year is
called a sunpath diagram. For example, a sunpath for San Francisco, California that was gener-
ated by the SunEye is shown below:
Figure 4-1.
The SunEye automatically generates the sunpath diagram for the particular latitude where the
data is collected. This sunpath chart is superimposed on top of the captured skyline image.
N O T E The annual sunpaths are drawn in standard time and the exported *.csv data files are also in
standard time. Daylight savings adjustments must be applied manually where appropriate.
Shading
Shading is a serious design parameter to consider with regard to the performance of a solar sys-
tem, placement of a building, or in landscaping. The
Solar Living Source book by John Schaef-
fer, comments on shading of crystalline PV collectors, “Short of outright physical destruction,
hard shadows are the worst possible thing you can do to a PV module output.”
Shading may be produced by geological formations, vegetation, and human-made structures,
such as buildings. Minor shading can result in a significant loss of energy. This is because the
solar cell with the lowest illumination determines the operating current of the series string in
which it is connected. The voltage output may remain the same, but the current will be signifi-
cantly reduced.
The SunEye automatically gives an accurate analysis of the shading for the specific location.