|What angle from a solar panel receives the most
power from the sun? My groups hypotheses is a 60*
angle but so far from now a 90* angle is receiving
more power, WHY?`|
|Question Date: 2015-02-05|
I think it's awesome that you're actually trying
this experiment out for real - great job at doing
real science! So let's try to understand what's
happening. A solar panel generates energy from
sunlight, right? So it will generate the most
energy whenever it's receiving the most light.
So then the question becomes: at what angle
will the solar panel receive the most light?
Well, there's an easy way to check this at home.
Take a sheet of paper and hold it out in front of
you. Imagine the sheet of paper is a solar panel,
and your head is the sun; in order for the sheet
of paper to receive the most light, you need to
rotate it so that the paper has the largest area
possible (that means it'll receive the most light
from your head).
So start looking at the paper edge-on; then the
area you see is really tiny (you just see the edge
of the paper). But if you start to rotate it, you
see more and more area. When do you see the
most? It should be when the paper is
facing you head-on; that is, when the paper is
angle at ninety degrees.
So that's why a solar panel receives the most
power from the sun when it's angled at ninety
degrees: that's when it has the most area
exposed to sunlight, so it captures more energy.
Great question! Solar panels always receive the
maximum power when the Sun is directly overhead
(90 degrees). This is because the Sun’s
rays have to travel through the atmosphere first
before reaching the solar panels. The atmosphere
absorbs a good part of the solar power. In fact,
there is a numerical coefficient that is used in
typical calculations of solar power efficiency
called the Air Mass (AM). When the Sun is
directly overhead AM=1.
However, because the Earth rotates and its tilt
varies throughout one year, the Sun will
invariably have to pass through more atmosphere
during the day and throughout the year. The
accepted “average” atmosphere that the Sun will
pass through is AM=1.5. This is about an angle of
48 degrees. Scientists use this value when testing
their solar cells to take into account atmospheric
If you wish to align solar panels in order to
receive maximum power throughout the day, you
would want to place the solar panel such that
it is perfectly aligned (90 degrees) with the
Sun at high noon (when the Sun has to pass
through the least atmosphere). This will vary
depending on your location and time of year. This
is because commercial solar panels are likely
designed with internal reflectors or mirrors that
bounce unabsorbed light back into the panel so
that more can be absorbed. At any angle but 90
degrees this mirror effect will be reduced, thus
giving you less power.
90 degrees. The reason is something you
will learn in geometry: at any distance from the
sun, there is a sphere over which all of the sun's
power is distributed. This sphere has an area. If
you hold a flat surface to collect some of that
power, and hold it perpendicular (i.e. 90-degree
angle) to the sun's light, then that flat surface
will be almost exactly fitting a tiny portion of
that sphere, and thus collect the power of that
portion. Tilt the surface so that it is not on
that sphere, then the cross-section of that
surface and the sphere is diminished, and so is
Here's another way to imagine it: imagine
looking at a flat surface from some distance away.
It will take up some part of the field of your
vision. It will take up the largest field of your
vision (i.e. appear to be the largest) if it is
perpendicular to the line drawn between it and
your eye. Now, if your eye were emitting light
like the sun, then the power that this surface
would receive would be in proportion to the amount
of the field of your vision that it takes up.
Thus, a perpendicular surface would get the most
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