POWER September 2015 - 34

TOP PLANTS
Panda Temple I and Panda
Sherman Combined Cycle Plants,
Texas
Owner/operator: Panda Power Funds
Courtesy: Siemens
A market desperate for new capacity. A highly challenging financing environment. A
grid with rapidly expanding intermittent wind generation. ERCOT needed solutions.
Panda Power Funds, Siemens, and Bechtel teamed up to make it happen with a pair
of highly responsive combined cycle plants.
Thomas W. Overton, JD
I
n the early 2010s, the Electric Reliability
Council of Texas (ERCOT) was staring
down the barrel of dangerously low
reserve margins, a combination of growing
demand and an energy-only wholesale market
that was having serious problems adequately
incentivizing new generation. In a
well-known incident in the summer of 2011,
ERCOT was forced to cut power to a number
of large industrial users and bring two retired
plants out of mothballs to avoid rolling blackouts
at the height of a heat wave.
More bad news came in early 2012, when
an ERCOT report warned that the state's reserve
margin-then hovering around 13%-
could drop into negative territory in as little
as a decade, and would fall under 7% by
2015. And even that narrow margin was an
improvement from a winter 2011 assessment
that pegged it at under 4%.
The difficult environment for financing
new plants was a hot topic of debate during
this period. With the falling price of natural
gas depressing power prices, traditional
generating firms loudly complained that
financing a new plant was simply too difficult,
arguing that returns in the existing
market were not competitive with other investments.
Many believed the solution was
implementing some type of capacity market,
a proposal others considered borderline heresy
(see " Challenges Facing Power Generators
in ERCOT " in the August 2013 issue and
" Texas and the Capacity Market Debate " in
the February 2014 issue). The Public Utilities
Commission of Texas, which opposed such a
34
move, instead voted in late 2012 to raise the
caps on wholesale prices from $3,000/MWh
to $9,000/MWh starting in 2015.
What a difference a few years makes.
ERCOT said in its Summer 2015 Seasonal
Assessment of Resource Adequacy that its
reserve margin this summer would be around
12.5%-still tight, but substantially higher
than what had been predicted in 2012. Some
of that improvement is due to lower-thanexpected
demand growth, but the extra generating
capacity now available is in large part
due to just two plants that added more than
1.5 GW of generation to ERCOT. Dallasbased
private equity firm and independent
power producer Panda Power Funds got the
two plants up and running in only two years
and did it in a financing environment that
more risk-averse established firms continue
to struggle with.
High-Power, High-Speed Plants
On the outside, the nearly identical Panda
Temple I (Figure 1) and Panda Sherman
(shown in the header photo) plants, the first
about an hour northeast of Austin and the other
about an hour north of Dallas, are typical
combined cycle power plants. What makes
them special is what goes on inside and how
they got where they are.
The two 758-MW, 2 x 1 projects are highperformance
Siemens Flex-Plant 30 facilities
able to start faster and ramp faster than earlier
designs, while maintaining strict emissions
compliance and high efficiency. The gas turbines
can begin generating electricity in 10
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minutes, can reach 60% load (220 MW) in 20
minutes, and hit full load within 30 minutes,
with the plant reaching full combined cycle
power production in under 60 minutes.
At the heart of the multi-shaft plants are
two Siemens SGT6-5000F gas turbines, each
of which feeds an NEM USA Benson heavy
duct-fired heat recovery steam generator, with
the steam powering a Siemens SST6-5000
steam turbine. Siemens also supplied the generators,
instrumentation, and control system.
The gas turbines are equipped with Siemens'
Shaping Power feature, which enables
faster ramping without negatively affecting
turbine life expectancy. The design extends
the operating range of the turbine by combining
a larger compressor with multiple rows of
variable compressor airfoils. From the baseload
design point, the turbine can quickly
ramp down by closing the variable airfoils
and quickly ramp up by using the additional
mass flow through the oversized compressor.
The design incorporates two other key features.
First, the oversized compressor adds
generation in excess of the baseload power,
even when ambient temperatures are high-a
key concern in Texas, where summer temperatures
regularly top 100F. Second, significant
amounts of power can be quickly and predictably
ramped up and down to respond to
intermittent renewable generation-also very
important in the wind-heavy ERCOT market,
which manages more wind generation than
any other independent system operator. The
response time is enhanced because the bottoming
cycle is already warm and the steam
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POWER September 2015

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