Tight Solar Schedule
Electric faced a very tight construction schedule in building the
PV solar project in California, a 6.7 MW project for Southern
California Edison in the town of Porterville.
To build a utility scale solar power park, and finish it on time, takes
a well-orchestrated plan with all parties reading from the same score
courtesy of Michael Crawley
But erecting a 6.7 megawatt facility in one-third to one-half of the
typical timeframe—as Cupertino Electric did in Porterville,
California, for Southern California Edison (SCE)—takes an
overdrive speed that musicians refer to as prestissimo.
also takes pre-planning, thinking ahead, and using vendors you know can
meet your time schedules, says Meisa Kassis, project manager for San
Jose-based Cupertino Electric Inc., electrical contractor on the
were awarded the bid on Thursday and had to mobilize the following
Monday, so we didn't have very much time," Kassis says. "In the
interim, we were thinking about it, but really, we had very little
time. Luckily, Cupertino Electric has a lot of internal resources that
make it possible to do a project like this one."
it was dedicated this past February, the multi-million-dollar
Porterville project was the largest utility-owned PV project in
ground-mount Porterville project is located in the southern end of
California's Central Valley, a predominately agricultural region. The
town of about 55,000 was chosen for a large-scale solar-generation site
because of suitable land, distribution circuits that can support a
large amount of solar power without the need for major costly upgrades,
and anticipated future power needs, says Gil Alexander, a spokesman for
SCE. Porterville city leaders were willing to work with the utility to
draft a suitable lease for the land adjacent to the airport on which
the PV system was built.
the 11 large-scale PV projects SCE had in the works at the time, the
Porterville project was the only ground-mount; the remainder were all
roof-mounts. All of the projects are part of a larger effort by the
utility to build and own 250 MW of solar generation within the next
five years. In addition, SCE will execute power purchase agreements
with independent power producers that represent another 250
in 2008, SCE's initiative will eventually create a network of mostly 1
to 2 MW rooftop and ground-mount solar power plants throughout the
utility's Southern California service region. The California Public
Utilities Commission approved the program in June 2009.
many earlier solar plants that fed electricity into a main substation
for transmission, most of SCE's projects will connect directly to the
nearest neighborhood power circuit, eliminating the need to build new
transmission lines or upgrade existing substations, Alexander says.
the California Renewable Portfolio Standard, utilities were required to
derive 20 percent of their power from renewable sources by 2010. A new
law passed by the California Legislature raises that to 33 percent by
2020. And the network of solar generation plants, including the
Porterville project, will go a long way to helping SCE meet those
goals, he says.
began talking to Porterville city leaders in 2009 about a 20-year lease
for 32 acres adjacent to the city's airport. The parcel was zoned
industrial so the land didn't have to be reclassified.
The utility issued a request for proposals during summer 2010 and
awarded the bid in late-September, with project completion in three
a 6.7 megawatt solar power facility in one-third to one-half of the
typical timeframe—as Cupertino Electric did in Porterville,
California, for Southern California Edison—took pre-planning,
thinking ahead, and using vendors Cupertino Electric knew could meet
their time schedules.
The short building phase was possible because of careful
pre-construction planning, which took more than a year, as well as
lessons learned about installation efficiencies at Edison's previous
solar facilities, Alexander says. He adds, "SCE always attempts to
minimize on-site construction timeframes to minimize the impact on the
From the time it submitted a bid until the time it was awarded, Kassis
says Cupertino was pre-planning the project.
When it was awarded the contract for electrical services, Cupertino had
to hire a total of 125 electricians through the International
Brotherhood of Electrical Workers Local 47. Typically, they would need
about 50 workers for a project of this size.
"So a lot of our labor force were unknown folks from Local 47," she
says. Cupertino always had one of their foremen on site to supervise
the crews, and Kassis credits the union electricians for their
professionalism in overcoming the project challenges.
The Porterville project was constructed concurrent with Cupertino's
work on two other SCE roof-mounted projects totaling 7 MW.
"Adding to the complexity, we had three going on at the same time with
very similar needs," Kassis says. "But Edison is good about providing
information in a timely manner" to keep the projects moving forward.
In its favor, the San Jose firm had just completed a 1 MW
design-and-build PV project in Northern California.
"We had learned engineering best practices that made a project more
constructable, so this helped us fast track this project," she says.
With the Porterville project, for example, Cupertino brought in a
larger trencher that could cover ground faster than a typical trencher.
Despite the tight time frame, Kassis says safety was always at the
"Safety is a big deal for us," she says.
The Porterville project involved 29,428 Trina TSM-PA05 230W modules,
which had to be shipped in containers from China. They arrived at the
Port of Los Angeles and were trucked approximately 320 miles to
"We would have four, five, or six containers coming out of the Port of
Los Angeles, most just-in-time deliveries," Kassis says. "We like
just-in-time so you don't have a lot of material sitting on the site,
just for security reasons alone."
What was out of Cupertino's hands was the actual product availability
and delivery schedule.
"When you have 7 to 20 MW coming from overseas, sometimes you're kind
of constrained by those delivery dates and the manufacturing capacity
for those solar modules," Kassis says.
Construction began in October 2010 and coincided with one of the
rainiest winters in California history.
"The record-breaking 100-year storms and rain levels presented even
more of a challenge," she says. "We worked in the rain when we
typically wouldn't have worked in the rain, just to keep on schedule.
You lose productivity in the rain—it's definitely not ideal
When it wasn't raining, Cupertino had to pay attention to dust being
generated by the delivery trucks.
The San Joaquin Valley Regional Air Quality Board requires dust
mitigation, either using water trucks to spray water on dirt roads or
using a polymer dust-reduction agent.
"Because of the nearby orchards and cotton fields, we were very
sensitive to the farmers," Kassis says of the dust concerns.
California Edison began talking to Porterville city leaders in 2009
about a 20-year lease for 32 acres adjacent to the city's airport for
the solar power project. The parcel was already zoned industrial so the
land didn't have to be reclassified.
In addition to a dust-control plan, Cupertino also implemented a storm
water pollution prevention plan to address any runoff from the project
Schletter Inc. of Tucson, Arizona, supplied the racking for the system,
which involves a 25-degree fix tilt. Satcon Technology Corp. supplied
Unlike many utility-scale PV systems that feed into a substation, the
Porterville project feeds directly into neighborhood lines—a
task easier said than done.
Supplying electricity locally eliminates the need to upgrade lines or
substations, SCE's Alexander says. But neighborhood lines aren't
designed to carry millions of watts of intermittent electricity from
solar-generation facilities. Solar power generation fluctuates and
peaks during mid-day. It can wane due to cloud cover or dense fog or
stop completely during the night.
To handle these electrical spikes that could wreak havoc with
residential and commercial electrical appliances alike, SCE is working
with the industry to develop smart-grid technology.
New circuit designs would instantly adjust and compensate to varying
power levels without even the most sensitive appliance registering it.
When it embarked on a goal of developing 250 MW of utility-owned PV
generation, SCE officials predicted the company could lower the cost of
construction from the industry prevailing $7 per watt to about $3.50
per watt. As the projects continue, Alexander says SCE is edging closer
to realizing those savings because of economies of scale.
"One way of understanding economies of scale is the experience many of
us have on a weekly basis—buying household supplies from a
‘big box' store," he says. "We've learned that we can pay
much less for paper towels if we are willing to buy them in much larger
quantities than we would at our neighborhood grocery store.
"Other cost reductions were also achieved via various engineering
improvements made and equipment standardization across our various