12:28 pm - 76 degrees - sunny...
Most off-grid homes use a wide
range of energy resources, in sharp contrast to the typical all-electric
suburban home. One energy resource that
we are using is solar power.
Solar power is produced by
collecting sunlight and converting it into electricity. This is done by using solar panels. Solar panels are large flat panels that are
made up of many individual solar cells. Lots
of small solar cells spread over a large area that work together to provide
enough power to be useful. The more
light that hits a cell, the more electricity it produces.
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| photo source: alternate energy info |
Once you have assessed your
solar power needs and the amount of solar gain you can expect, the next step is
figuring out where and how to mount your solar panels to get optimum light
exposure. There are a numerous ways to
mount solar panels, and the best choice depends not only on maximizing exposure
over the course of a year, but also cost and practicality. Depending on city or county code
requirements, that can sometimes mean thousands of dollars in engineering and
equipment. When all is said and done,
simplicity is key.
Two important things to keep in
mind when you’re looking at where to place your solar panels are which
direction the solar panels should face and the optimal angle the solar panels
should be tilted.
Where to place your solar
panels - in general there’s one big rule: if you’re in the U.S. (or anywhere
else in the Northern Hemisphere), your solar panels should face true south (aka
solar south or geographic south).
Identifying true south is not
as simple as using a compass. Due to the
imperfections in the composition of the earth, due south rarely matches the
compass reading. A compass points toward
the south pole of the earth’s geomagnetic field. It’s the right general direction – but not
exact.
A simple method to finding true
south is to look at your house on Google Earth; after centering the image on
your home, you can view the north-south grid lines Google provides. In the View menu, select “Grid”.
Another easy way to identify
true south is to look in your local newspaper (or Google) for the exact time of sunrise
and sunset for that day. Calculate the
middle of these times; it should be somewhere near noon, but rarely right at
noon. Stick a pole in the ground, and at
the exact middle time between sunrise and sunset, the shadow from the pole
lines up with due south.
Once you have the direction the
solar panels should face, next comes finding the optimal angle the solar panels
should be tilted to get the best out of your system.
The optimum angle varies throughout
the year, depending on the seasons and your location. Of course, the sun is continually moving
throughout the day and to get the best from your solar panels you would need to
angle your panels to track the sun minute by minute. You can buy an automated solar tracker to do
this but unfortunately, the expense of a tracker means that for most systems
they are more expensive than buying additional panels to compensate. The amount of power a solar tracker uses in
order to track the sun also negates much of its benefits.
The sun is at its highest at
solar noon each day (this occurs exactly half way between sunrise and sunset)
and by using a Solar Angle Calculator {Click Here} you can find out the angle
at that time of day. At solar noon, the
irradiance from the sun is at its very highest and you can generate the most
power. In the northern hemisphere, the
sun is due south at solar noon.
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| photo source: gogreensolar.com |
If you want to get the best performance
during the summer months, you would angle your solar panels according to the
height of the sun in the sky during these months. If you want to improve your winter
performance, you would angle your solar panels towards the winter months in order
to get the best performance at that time of year. If you have the opportunity to adjust your
solar panels throughout the year, you will benefit from having the optimum
angle on a month by month basis.
After all that has been said,
here is what we did – simplicity is key after all.
We picked up 8 solar panels
that are roughly 2’6” x 5’6” for free.
We know nothing about them other than they were for a 12 volt
system. Free is a very hard price to
pass up especially when to buy them new would be a minimum of $1,600.
Not knowing anything about the
panels and how well they would perform, we didn’t want to spend a lot of money
on a mounting system. So Tony came up
with a design using scrap materials that we had lying around the house.
This simple design allows them to be moved around on the forks of a tractor if we deiced we want to place them in a different location.
The orchard crates will be partially filled with large stones found around the property to counter weight the solar panels and anchor them down for high winds.
This simple design also allows the solar panels to be adjusted for optimum positioning in any direction and angle.
We're half way done. Need to build two more racks and then onto the wiring.
