CLICK See a slide show and interact with Seth Masia at solartoday.org/paonia
under-roof wiring. Rick Basler hooked up the
disconnect box.
After lunch we traded places. Rick, Todd
and I climbed onto the roof to bolt down the
second row of five modules and complete the
electrical connections. We later measured the
temperature of the sun-blasted modules at
42°C (108°F), and the asphalt shingles were
not cooler. I spent an unpleasant 15 minutes
lying flat on my back in the roasting pan, fishing about under the array to snap in the last
plugs and tie up loops of cable. Then Kyle
walked us through commissioning and testing. Brendan donned the insulated gloves to
make the final connections and turn on the
disconnect. Nothing smoked.
projects and got explanations from their crews.
The pole-mount gang seemed happiest: Their
system went up quickly, and they finished the
wiring standing up straight in the shade of their
own modules.
Then it was teardown time. We made short
work of this: Systems came apart more quickly
than they went up because we didn’t have to
align anything. The only tricky bit was disconnecting the module cables from the microinverters. You need a special tool to disengage
two hooks on the locking connectors. One of
the joints stuck and needed four-handed fiddling using hook-nosed pliers.
By mid-afternoon the solar ovens filled
up with casseroles, ears of corn and a broiler
chicken for the evening potluck supper, with
spouses and offspring of the instructor staff
in attendance.
The course prepares
students for the North
American Board of Certified
Energy Practitioners
(NABCEP) entry-level exam
System Gets an A, “Not an A+”
On Wednesday morning, Kris inspected
our Enphase system and gave us an A. “Not an
A+,” he pointed out. Near the junction box,
we’d left too much cable to stuff into the rack
rail channels, so I’d fastened the excess up with
wire ties. Perfectly safe and workmanlike, but if
it were my roof, I’d have cut it to proper length
and crimped on new connectors.
After lunch we toured all five completed
Grid Simulator Installs Quickly
The groups reorganized for Thursday and
I went with instructors Brad Burkhartzmeyer
and Brady Bancroft to learn about the elaborate Sunny Island system. This hybrid charge-controller/inverter was devised by SMA for
isolated stand-alone power systems. If you
lived on a mountain top or in a remote village
far from any grid, you’d want a Sunny Island.
The main box simulates a grid, imposing a
sine-wave voltage on any current coming in.
Any peripheral inverter will see it as a grid and
cooperate. You can send in power from a PV
array, microhydro generator, wind turbine,
battery array or straight from a real utility grid.
Assuming more than one power source, if any
one goes down, the Island keeps sending out
“grid” power.
The cool morning turned into a hot midday. Happily, we didn’t have to work on a roof.
The system’s DC side is fed by a 1.6-kilowatt
ground-mount array, built as a single string
of eight Sanyo bifacial modules. We got it
up pretty quickly. Brendan Pattison and Dan
Michelson wired up the DC and AC disconnects, while Scott Ostrin and I bruised the
heels of our hands plumbing up the rack. I’d
add a 10-foot straight-edge and a rubber mallet
to the tool kit.
We reconvened in the evening at Paonia’s
Revolution Brewery, a tiny bar in what used
to be a tiny church. It’s what Alice’s Restaurant must have looked like. The microbrew of
choice is SEIPA — Solar Energy International
Pale Ale.
With the actual temperature of the array in
hand and a reading of actual watts-per-square-meter in the late afternoon sun, we predicted
a system output for the time of day — about
1,330 watts. The Enphase inverters send data
out through their AC cables, so the system provides a nifty web-based readout of real-time
performance, module by module. By the time
we got data flowing through the Mac interface,
it was almost 5:00 p.m., and the modules generated about 1,200 watts. Kris showed us the
log for the previous month’s power output. It’s
very cool to see the diurnal curve of power in
a weeklong chart.
Solar tabby is best-in-class at finding shade.
Course Ends; Many Stay For More
I had to ask the instructors: What’s the
toughest concept to get through to students?
“Solar Kelly” Larson from Northern California didn’t hesitate: “Wire sizing,” she said.
“It’s just difficult to account for all the variables
that go into determining a safe and efficient
gauge for each wiring application.”
Kris Sutton said, “Magnetic declination,”
the difference between true south and magnetic south. Guess which one you need to maximize solar gain? In Paonia, the declination is
12 degrees east. Get it straight before you go
drinking with Kris.
Most of the students had now been in Paonia for two weeks, and many were staying on
for the advanced course the following week.
That course focuses on the intricacies of the
National Electrical Code.
Friday morning saw final wiring and
adjustments on some of the lab projects. Our
group spent part of the morning figuring out
the voltage drop in the #8 AC line from the
PV inverter to the Sunny Island. Then we connected the microgrid inverter to the 48-volt
battery bank, the grid transformer and the
PV array inverter. We turned everything on
and waited 10 minutes while the Sunny Island
exchanged data with the other units and came
on line.
After lunch, Ed Eaton convened a study
group for students taking the NABCEP test
that evening. The rest of our group put together a schematic of the Sunny Island rig, suitable
for use in explaining the complex system to
an inspector.
At 3: 30 p.m., Kris, Flint and Kyle conducted a casual graduation ceremony. They handed
out the certificates, and everyone promised to
let each other know when we found rooftop
work. Then we rode off into the sunset. ST
