Mounting Design for Harbor Freight Solar Panels
by Michael Shaw, May 2013
Harbor Freight sells an
economical solar energy kit that I bought several years ago for less than $200.
This kit is advertised as a 45 watt DC system that contains three solar panels,
a charge controller/DC supply unit, two 12VDC lamps and all the wiring needed. The
only thing you need to supply is a 12VDC car battery. For several years I used
it as an auxiliary power source after several hurricanes struck south Florida
in 2005 (see my June 2012 blog post “Notes on Surviving a Hurricane”). But what
I really wanted to do is get more use from them, so I decided I would use the
system to create power for a remote utility shed in the back yard. It could be
used for interior or exterior lights, or to power an outdoor fountain or even
for 12VDC ventilation fans inside the shed. The only problem was the mounting
brackets that came with the kit were really only meant for temporary use and
not for a permanent setup. What I needed was an inexpensive and secure way to
mount the three panels on the roof of a corrugated aluminum roof shed.
I decided to make my own
mounts after searching the web for affordable PV mounting brackets. Most of the
mounting hardware I found on the web was for mounting standard PV panels with
higher wattages and dimensions of around 39”X64”. What I wanted didn’t exist,
so I decided to make my own. What I needed was a design that was light-weight, wouldn’t
rust and could be mounted on a corrugated shed roof, and, oh yeah, cheap. After
wandering the local Home Depot store I came across some aluminum metal stock
that would do the trick.
What my wife and most
females don’t understand about men is that when we walk the isles of a store, in
particular a hardware store, our minds are in “tool acquisition” mode. What we
are doing in this mode is looking at everything available in the store
and deciding if it is A) something that looks cool, B) could it be useful as a
weapon or a tool and C) can be turned into something that could be useful as a
weapon or a tool. That is why it can take us hours to pick up “some screws” at
the local hardware store. So now you know, deal with it.
The aluminum C channel stock
I bought would be used as the rails to mount the panels on and the square stock
I bought would be used as mounting brackets and act as spacers between the
corrugated sections of the roof. I put it all together using stainless steel
nuts, washers and screws. The following drawings show how it all came together:
A 96” length of “C” channel stock was cut to span the length
of the 3 panels with about .25” between the panels for the ¼ X 20 screws. I cut 4 pieces of the ¾” X 1/16” square
tubing at about 0.89” in length for the end stand-offs, and 4 more pieces about
1” in length for the mounting brackets. Then
I used 4 1/4X3” lag screws and washers to secure the rails to the roof of the
shed as in the picture below.
I mounted the rails so they were conveniently located over the center of the roof support beams (this is identified by the location of the roofing screws securing the roofing panels). Then I caulked the bottom of the mounting brackets and used aluminum tape around the bottom of the mounting bracket to act as flashing to keep the mounts from leaking when it rains.
With the rails mounted it was time to install the panels.
It’s easier to put the ¼ X20 screws between the panels in before installing the
panels, that way all you have to do is slide the panel under the screw. It’s
hard to screw the nut, lock washer and flat washer onto the end of the screw
after the panels are in place.
Once the panels were in place, I ran the individual wires
from the panels to the junction box where I connected them in parallel using a
terminal strip I bought at Radio Shack and mounted inside the junction box.
Then I ran a cable from the junction box up under the roof and down to the controller inside the shed.
In the completed mounting design, as a safety measure I attached a bare copper wire to the solar panel mounting rails and to a grounding rod driven 6’ into the ground at the corner of the shed (not shown). This protects the system from the possibility of lightning.
The system has only been in place for about a month, but it should last for many years to come.
