POWER September 2014 - 28

TOP PLANTS
the California Energy Commission (CEC)
that June.
The 37-acre site-surrounded on all sides
by wind turbines-was chosen because of a
number of advantages. Though greenfield,
the area was zoned for industrial use and
would have only limited environmental impact.
One of the SCE substations that gathers
generation from the area wind farms is about
700 feet away, and the natural gas supply line
could be extended from a small peaker plant
a few miles further on.
But despite the advantages, the project
soon ran into a completely unrelated roadblock
that halted development for more than
a year. In August 2007, the South Coast Air
Quality Management District (SCAQMD),
which oversees emissions permitting in the
area, amended its rules for how it issued offset
credits for proposed power plant emissions.
The new rule was challenged in court, and
in June 2008, the California Superior Court
threw out the revised approach, which meant
that the SCAQMD had no authority to issue
credits until a new rule was in place. Projects
without emissions permits, like Sentinel,
had no way to go forward unless they could
purchase the credits on the open market-a
very expensive proposition. The SCAQMD
appealed the decision, but lost.
The threat this ruling presented to generation
planning in California caused the state
legislature to pass a law in September 2009
allowing SCAQMD to issue a limited number
of unreleased credits. Permitting for Sentinel
was then able to resume, and the CEC issued
final approval in December 2010. This cleared
the way to close financing on the $900 million
project the following May. GE Energy Financial
Services and Diamond Generating Corp.
(DGC) joined the project, with a total of 23
banks providing nearly $800 million in credit
facilities. (In fact, interest in the project was
so high that the syndicated loan was 2.4 times
oversubscribed.)
A Big Niche
Gemma Power Systems was awarded the
engineering, procurement, and construction
contract, and ground was broken in
July 2011. Construction proceeded ahead
of schedule, and the plant was able to begin
testing of the first three turbines in January
2013. Though completion was originally
planned for late summer, the plant reached
commercial operation in mid-May, more than
three months early. This was despite having
to conduct much of the construction at night
or in the early morning hours because of high
temperatures during the day.
In all, 350 direct and indirect jobs were
created by the project, and more than 731,000
man-hours were put in. The plant is now
28
1. Eight-pack. One of CPV Sentinel's eight GE LMS100 gas turbines is lifted into place
during construction. The site is completely surrounded by wind turbines that make up the San
Gorgonio Pass Wind Farm. Courtesy: CPV
jointly owned by CPV (which serves as plant
manager), DGC (which operates the facility),
and other private investors.
The 800-MW CPV Sentinel plant is designed
from the ground up to be a fast-responding,
environmentally friendly facility.
Power is provided by eight General Electric
LMS100 aeroderivative gas turbines
operating in simple cycle mode (Figure 1).
Emissions are kept low through the use of
water-injected combustors with selective catalytic
reduction and oxidation catalyst.
To maintain efficiency in an environment
where ambient temperatures can exceed 120F,
the turbines employ evaporative cooling for
inlet air as well as intercooling. Hot air from
the first compressor section is passed through
an external water-cooled heat exchanger before
being returned to the compressor. Cooling
for this and other processes is provided
by single-cell cooling towers (one for each
turbine) using recirculating water. The plant
employs membrane-based wastewater treatment
processes coupled with a crystallizer
zero-liquid discharge system to handle project
wastewater.
To reduce its impact on local water supplies,
CPV Sentinel purchases water for the
local Desert Water Agency (DWA) equal to
108% of its use. The project has also funded
a variety of water efficiency measures for
DWA to minimize its impact on scarce local
water supplies. The arrangement has already
recharged the local aquifer with more water
than the plant is expected to use during its
first 10 years of operation.
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The state-of-the-art facility requires a staff
of only 14. Output can range from 50 MW to
800 MW, and the LMS100 turbines can reach
full output from cold start in as little as 10
minutes. The use of multiple small turbines
allows the plant to maintain better than 41%
efficiency from 100 MW all the way up to
full power. Each unit can be dispatched and
controlled independently.
Carrying Its Weight
CPV Sentinel's generation has helped reduce
the risk of brownouts and instability during
periods of high demand from the area's fierce
summer heat. It's also increased the California
Independent System Operator (CAISO)
and SCE's ability to integrate additional renewable
generation as part of plans for California's
2020 RPS target.
As a peaker plant, CPV Sentinel's generation
is capped at 30% yearly capacity factor
and a total of 300 starts and 2,500 hours of
operation per year. In its first year, it has been
dispatched frequently and has seen better
than 99% availability. In addition to generation,
the plant is providing spinning and nonspinning
reserve and frequency regulation
services for CAISO and SCE.
For serving as a key element in Southern
California's reliability planning and completing
this low-impact project ahead of schedule,
CPV Sentinel is recognized as a POWER
Top Plant. ■
-Thomas W. Overton, JD is a POWER associate
editor (@POWERmagazine,
@thomas_overton).
POWER | September 2014

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POWER September 2014

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