Tom Moates guide shows you how to build a manual solar tracker–cheap, rugged . . . perfect.
The first winter on our homestead was rough. The snows were
the worst anyone could remember in these Blue Ridge
Mountains of Virginia, and aside from the house being
completely incomplete and without running water, the solar
panels–our source of electricity–were , sitting
on the ground, leaned up against a camper shell to do their
collecting. When spring finally sprang permanently,
mounting our photovoltaic array was a priority we could no
longer put off, even though our funds were seriously
depleted. No longer could we afford weeds climbing in front
of the modules, tree shadows, and dog traffic–all
debilitating our current generation as water pumping and
clothes washing became a regular in-homestead event.
The treetops around the homestead remained bright with
sunlight for awhile after the sun dropped behind the higher
surrounding ridge for the evening, so it was obvious a tall
mounting pole would help harness more power each day. Also,
we explored the benefits of panel mounts that track the
sun. The pros say that in the winter, a tracking array in
an unobstructed spot produces at least 15 percent more
power than a stationary model; in summer, that figure jumps
from 40 to 60 percent. This is a substantial gain, but we
simply couldn’t afford a self-tracking mount–which
would have been more than $1,000 for one large enough to
house all our panels.
Carol, my wife, brought to my attention the key to solving
the dilemma. “With the animals and gardens,” she said,
“someone is usually here–couldn’t we turn them?”
Of course! A manual solar tracker–cheap, rugged . . . perfect.
For pennies compared to the factory built self-tracker, I
designed and built a manual tracker large enough to handle
our current 18 panels as well as 12 additional panels we
hope to add one day, and used material we already had on
hand.
The design is simple. The sun makes its journey across the
sky in an orbital path, so the solar array needs to track
in that same way. Also, the sun tracks much higher in the
sky during the long days of summer (figure the angle by
subtracting 15 degrees from your latitude) than in the
shorter winter days (latitude plus 15 degrees). To maximize
full frontal angle to the sun, the array also needed to
tilt up and down to allow for this seasonal change.
Adjust the size of the tracker in this article to fit your
needs. The total area of our panels is about 60 square
feet, but an upgrade to 120 square feet was allowed for, so
the overall size of the tracker is 10 foot by 12 foot though it
isn’t all used yet.
The basic skeleton of the apparatus is six long pieces of
angle iron drilled and bolted together. A pivot cap is
needed for the top of the pole where the whole thing hinges
for the up and down winter/summer adjustment. Three small
angle pivots are needed for the daily orbital swinging of
the array. Four rough oak 1 by 4’s act similar to roof
purlins and allow for the mounting of the panels
themselves. Finally, a hand winch is attached to the base
of the pole, and cables are run to allow the whole thing to
turn on its hinge points when the winch is cranked and the
top of the pole is guyed off to the ground for stability in
wind.
Manual Solar Tracker Materials
A straight 30-foot-long locust pole from a tree felled
while clearing for the garden was our choice to hold the
array. Choose a pole length that optimizes your sunlight
potential–either a wooden or metal pole will suffice.
A few bags of concrete are needed to set the pole in the
ground; you need enough to fill two-thirds of the hole
around the pole with concrete.
Aside from the photovoltaic panels themselves, the most
expensive part of the array is likely to be the angle iron.
Most areas have scrap yards, and it’s hard to say how much
you might have to pay for the pieces. Purchased brand new,
the galvanized angle iron for this project would cost about
$100, but there are bound to be sources for scrap in the
immediate vicinity.
Lag bolts, bolts, cable, and even the winch (refer to
materials list on page 88 for numbers of each) should be
available from most building or farm supplies. A catalog
company called Northern Hydraulics (Burnsville, MN) also has such supplies
at a reasonable cost.
Solar Tracker Construction
Much of the initial work involved in this project is
drilling bolt holes through the angle iron pieces. A drill
press and sharp bit helps speed up this task, but it can be
done with an electric hand drill. For each hole, take your
measurements, make a small indentation with a center punch
at the center point of the hole for the bit to follow, and
always apply light cutting oil to the bit and metal while
drilling (refer to the diagram depicting each piece with
size and positions of holes for layout). It helps to label
each piece of angle you have acquired with its respective
diagram number for reference during layout and assembly.
Also, a metal cutting bandsaw, a metal chopsaw, a cutting
torch, or even a grinder can be used to cut the angle iron.
The top pole pivot and the three identical frame pivots
require a bit of welding. Make sure all welds are done by
an experienced welder–a faulty weld could snap in a
wind with devastating results. The top pivot is a piece of
1/4 inch plate metal (4) cut slightly larger than the top of
your mounting pole, with four 12 inch legs (4c-4f) welded
across from one another that fit over the top of the pole.
Lag bolts screw through the holes into the pole to hold the
unit–and pieces 4a and 4b are welded back to back on
the other side of 4c. The 2 1/2 inch with the clips cut out and
bolt holes aligned together stick out beyond the edge of 4c
to allow for the hinging action of the entire array.
The frame pivots (5a, b, and c) are two short pieces of
angle with some edges trimmed, bolt holes drilled, and
welded into a “T”. The diagrams for the pieces show how
they should look when finished.
Solar Tracker Assembly
For simplicity, we fitted and mounted the top pole pivot
onto the pole before raising it. This allowed for an easy
work space but the overhang of parts 4a and 4b must be
oriented southward when the pole is permanently
set–which was difficult to maintain while setting the
pole.
With post hole diggers we dug a 6 foot hole and then, using a
gin pole, we hoisted the massive locust post into the air
and sank it into the hole. When setting your pole, use a 4′
level to maintain plumb while filling in around the base
with concrete. Then tamp rocks and dirt into the hole,
keeping true while filling it the rest of the way.
Once the pole is up, erect scaffolding along side of it to
provide a safe work space for the higher-altitude assembly.
The first piece to go up is the spine. It can be
pre-assembled on the ground; set 2a and 2b back to back and
bolt frame pivots 5a, 5b, and 5c in their positions on the
flat side of the spine. Use lock washers on the bolts and
tighten snugly. Notice that when the frame pivots are
installed, spine pieces 2a and 2b, though oriented back to
back, do not touch. This opening allows for the top pole
pivot (piece 4) to fit between 2a and 2b with a single bolt
passing through all four pieces (4a, 4b, 2a, and 2b),
creating the main hinge that holds the entire array. Pull
the assembled spine up the scaffolding, and bolt it in
place to the top pole pivot, making sure that the bolt hole
on the spine for the angle brace is facing the downward
side.
Bolt the brace (piece 3) to its hole in the spine, and then
lag bolt it back to the pole in a position that allows for
easiest access for installation of the remaining pieces
from your scaffolding. Notice the brace has multiple holes
on the end towards the pole; this allows for the adjustment
of the array for higher summer sun tracking or lower winter
sun tracking.
Next carry up and bolt the frame pieces in place (1a, 1b,
and 1c). Take care to mount 1b to the center frame pivot
(5b); this frame piece has holes drilled at either end for
attaching the turning cables. Snug these bolts down, but
not so excruciatingly tight that they won’t allow the frame
to pivot. Adding a bit of grease between the frame and
pivot will help the process as well.
Using 3/8 inch carriage bolts with lock washers, bolt the 1 by 4
oak purlins onto the frame. It may be easiest to C-clamp
the boards to the frame pieces in place, and then drill by
running the bit through the holes already in the angle
pieces, and bolt them from the scaffolding. Note that you
may wish to configure the purlins slightly differently than
we have to accommodate other kinds of panels. The important
things to keep in mind are that the array should be equally
balanced in weight on either side, and that the weather
tight electrical boxes on the back sides of the panels
should be kept to the side of the purlins for
accessibility. You also may want to treat the purlins with
a wood preservative before sending them up.
Using wood is nice because it allows for a certain amount
of flexibility in the rig. Different types of panels are
easily mounted. Some of our panels, for instance, have
aluminum frames with pre-drilled holes, which we attached
simply by drilling through the oak and fastened with
carriage bolts. The other panels only have small plastic
frames that were mounted with screws and neoprene washers,
pinching the edges of these frames in several spots.
With the wood in place, mount and wire your panels. Next,
attach an end of a piece of 1/8 inch cable to a hole at an end
of 1b using a cable eye and two clamps. Mount your hand
winch to a comfortable spot at the base of the pole. With
the array turned fully to the side where the cable
connection is up in the air, cut the cable at the winch and
connect it properly to the winch spool.
Now connect another cable to the hole in the other end of
lb in the same fashion as above, and crank the winch
turning the array fully to the other direction. Place a lag
bolt into the pole above the winch at about shoulder
height, cut the cable dangling from the side of lb now high
in the air, and put a loop in the end so that it may slip
over the lag bolt. When the array is fully turned with the
winch, the cable loop in the lag bolt will keep the array
snug so that even strong winds won’t swing it around.
Place lag bolts at several other positions down the pole so
that the loop on the loose cable may be changed from one to
another, effectively locking the winch on these positions
throughout the day. Be careful not to overtighten the rig
with the winch–just a little tension works fine.
Back at the top of the pole, attach at least three guy
wires to the top pole pivot with two clamps each. Run these
to stabs driven deeply into the ground (at least three
feet), and put turn buckles into the guy wires near the
ground so they may be tightened occasionally.
Finally you must protect the rig against lightning strikes.
Drive your 8 foot copper or galvanized ground rod into the
ground at the base of the pole. Bolt a large copper wire (I
used 3/0 copper and I wouldn’t suggest less than 1/0
copper) to the spine (2a), and run this down and attach the
other end to the ground rod. This is a separate ground from
your system ground and should take direct hits right into
the ground away from the system. We also have a system
ground connected to the negative side at the battery, have
fused disconnects coming from the panels on the positive
leg, and have a low voltage lightning arrester before the
fuse. This is an adequate ground. Some installations run
multiple ground rods from the array frame in every
direction, but this strikes me (sorry) as a bit of
overkill. The rod’s ultimate purpose is to discharge an
occasional and unwanted direct hit, not to provide
the ultimate encouragement and opportunity for every
passing thunderhead by saying, “Hey, look at this great
discharge spot over here!”
If you’re going to be away for the day, just leave the
array pointed south to maximize the stationary collection
of the sun. If you are expecting high winds, take time and
inspect the guy wires for tightness, and snug the array,
making it as parallel to wind currents as you can manage,
thus reducing stress on the panels.
The project took several days to fabricate and assemble,
but for a minimal cost we have maximized our photovoltaic
collection and built a tracker that has operated flawlessly
for more than six months and survived several gusty wind
storms without incident–testimony that cheap and
simple technology still can be the most appropriate
alternative for my good old average homestead, and maybe
yours, too.
