Take a walk up to any terrace and look at the solar panels. They look like slides, don’t they? Why ever is that? You would guess, correctly, that we want our solar panels to receive the greatest amount of sunlight. The sun does not rise in the exact east each day. The direction of sun-rise changes gradually from south-east to north-east and back again. The earth’s orbit around the sun is slightly elliptical and the sun is at one focus. That means, the earth is sometimes closer to the sun and sometimes further from it. Also, the earth’s axis is tilted with respect to the plane of it’s orbit. That means sometimes the southern hemisphere is closer to the sun and sometimes the northern hemisphere is closer to the sun. This link http://www.timeanddate.com/astronomy/india/bangalore gives us very nice information about the sun’s position in Bangalore each day. You can see that even at it’s peak the sun was not 90 degrees overhead today. Instead it’s highest point was 84 degrees and it occurred  slightly after noon (12:18 pm). You can also see that over the next week, the altitude reduces gradually to 82 deg and the solar noon occurs about a minute earlier.

Cause of Seasons: Image Source: http://csep10.phys.utk.edu/astr161/lect/time/seasons.html

All this adds up to a couple of  things.

  1. Over the course of the entire year, we can expect to receive more sunlight from the south, in Bengaluru. So our solar panels will face south.
  2. Solar panels generate the greatest voltage when sunlight falls on them vertically. By tilting the solar panels by the same degree as our latitude, we can gather the maximum sunlight on an average in a year. In important installations, it is possible to keep changing the angles of the solar panel throughout the year. In roof top solar installations, the panels are fixed at the angle equal to the latitude and facing south.


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