Racking: Solar Power Components – Part 3

Racking: Solar Power Components – Part 3


Hi. I’m Amy Beaudet from the altE Store. Thank
you for watching our video series, we’ve broken it down into multiple parts to keep it manageable.
This video is called “Solar Electric Components, Racking”. If you missed our previous videos,
I recommend you go back and watch the earlier ones in the series to get a good foundation,
including part 1 covering solar panels and batteries, and part 2 covering charge controllers
and inverters. Racking is a less glamorous, yet critical component to a solar system.
We’ll briefly go over three of the most common types of racking; roof, ground, and trackers.
So let’s get into some racking options. The first place people think about installing
solar is on the roof. There are options for installing on all types of roofs; including
asphalt or tile shingles, metal standing seam, and flat rubber roofs. Any roof penetrations,
including bolts for the mounting feet or the conduit going through the roof, must be flashed
to prevent leaks. There are several good options available depending on the type of shingle,
but we are not going to get into them for this video. When selecting a roof mount, you
do have the option of using legs to tilt the angle of the panels higher or in a different
direction if needed, but it is generally recommended that you just mount the panels flush on the
roof, and accept that it may not produce as much power as it would if at the idea angle.
Unless you have to squeeze out every last bit of power from the array, generally, a
flush mount looks better, and you don’t have to be concerned with additional wind loading
by being raised off the roof. Standing steam metal roofs need a solution that won’t drill
through the metal. Clamps are available to grab onto the standing seam, allowing you
to connect the rails, or the panels themselves, right to the clamp. Likewise, you don’t want
to drill through a flat rubber roof. A ballast mount allows you to weigh down the racking
with concrete blocks instead of bolting them to the roof. Ballast mounts are generally
tilted at a lower angle than a traditional roof mount, as it tries to reduce the wind
loading that could potentially move the array, since it is not bolted to the roof. There
are a lot of options for mounting the array on the ground. Smaller arrays can be mounted
on the side of the pole, larger ones, up to 18 modules or more, depending on the panel
size, can be mounted on the top of a pole. Pole mounts and some ground mounts provide
an adjustable option, allowing you to optimize the angle of the panels to match the seasonal
angle of the sun. Ground mounts give you options for very large systems, provided you have
the space for them. Carports provide shelter for your vehicle, while providing you power.
An awning mount on the side of your house can sometimes be an option when no horizontal
location is free. As you can see, there are many options available, not just on your roof.
Trackers will automatically follow the sun throughout the day from east to west, and
optionally change the tilt throughout the year as well. A passive tracker generally
has canisters with a gas inside, which changes weight as they heat up and cool down. This
causes the array to gradually move from east to west during the day, returning to east
by morning. This requires no electricity to track the sun throughout the day. Active trackers
have an electric motor that follows the sun east to west throughout the day. It can also
adjust the tilt seasonally. Active trackers are usually more expensive than passive trackers.
Depending on your location, a tracker can increase your output by as much as 30%. But
they also add complications to the system, adding a mechanical component that could potentially
fail. It’s often less money and less work to simply add 30% more panels to your fixed
system to increase the output. To help decide which racking is right for your system, let’s
talk about performance based on the angle of the array. For best output, you want the
sun’s rays to hit the array at a 90 degree angle. To figure out the angle you should
mount your system, know that generally, for a fixed mount, which is one that doesn’t get
adjusted seasonally, the best tilt is equal to your latitude. Here in Massachusetts, we
are at 42 degrees latitude, so the best angle to tilt your system is 42 degrees off horizontal.
If you have a system that you want to optimize for Winter output, squeezing every bit you
can out of the short day, you would tilt it an additional 15 degrees, at 57 degrees here,
to keep the panels pointing at the low winter sun. Since the sun is higher in the summer,
if you have a seasonal cabin that is only used in the summer, you would tilt the panels
15 degrees higher than latitude, or 27 degrees, here in Massachusetts. “Sun hours” uses a
compilation of historical weather data to determine the amount of solar energy available
at the solar array, based on Standard Test Conditions. Although the sun is shining for
12 hours, the intensity of the sun isn’t the same for all of those hours. For instance,
the sun is half as intense at 8:00AM as it is at 11:00AM, so from 8-9 would count as
half as many sun hours as from 11 – 12. This chart shows the sun hours of 2 extremes here,
Anchorage Alaska and Key West Florida, for an array that is fixed, or doesn’t move, and
at different angles in relation to the latitude, vs a tracker, one that automatically follows
the sun throughout the day, set at different tilt angles or one that automatically changes
the tilt throughout the year. It shows the sun hours per month, as well as an annual
average. This is very useful to determine the amount of electricity output you can expect
for your area, depending on how you rack the array. You can decide if it is worth the extra
money and effort to change the angle of the array seasonally, or if it makes more sense
to just set it and forget it, and size the array based on that angle. For example, you
can see that in Key West, setting a fixed array at latitude gives you an annual average
of 5.5 Sun hours. A single axis tracker also set at latitude would increase that by almost
30% to 7 sun hours, but going up to a dual axis tracker that also changes the tilt seasonally,
only adds another .2 sun hours on top of that, so it may not be worth it to you. As you can
tell, there are so many racking options available to choose from. Check out our website for
a great selection of racking and trackers available. lso watch more of our Video Series
on our web site to learn more about solar. e’ve got a team of highly trained Technical
Sales Reps available to help you plan your system, give us a call, we’d love to help.
And don’t forget to check out the rest of our site at altestore.com, where we are making
renewable, doable.

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