119
YEARS
Panda Sherman. Photo
courtesy: Panda Power Funds
COMBINED CYCLE:
The Preferred
Option
M
BY RUSSELL RAY, CHIEF EDITOR
ost new generation in the U.S. is
being fueled with
natural gas, and
the most dominant technology being used to burn
the fuel is combined cycle.
Combined cycle power plants are
highly efficient, allowing power
producers to wring much more power
from the same amount of natural
gas. The energy conversion rates for
combined cycle gas turbine (CCGT)
plants are high, ranging from 50 to
60 percent.
The number of combined-cycle
projects is expected to increase
3.1 percent a year through 2038,
according
to
a
report
from
engineering firm Black & Veatch.
In 2014, the U.S. added 15,450 MW
of new generation. More than half of
that capacity – 7,902 MW – was fired
by natural gas. What’s more, CCGT
technology accounted for 92 percent
of the gas-fired generation that was
brought online last year.
In 2035, power fueled with natural
gas is expected to surpass coalfired power as the dominant source
of power generation in the U.S.,
according to the Energy Information
Administration (EIA), the statistical
arm of the U.S. Department of Energy
(DOE). After 2020, power plants
fueled with natural gas will account
for 70 percent of all new generation
capacity, according to EIA.
By 2040, renewable power capacity
will grow 69 percent, which means
gas-fired plants must be fast and
f lexible to accommodate the growing
amount of intermittent generation.
The transition to CCGT technology
is being driven by low gas prices,
stricter regulation for coal plants, and
the integration of growing amounts
of renewable power. Combined cycle
plants compliment wind and solar
power because they can start and
stop quickly, and thus are capable
of offsetting the f luctuations in
renewable power.
The increasing use of CCGT
technology has led to a sharp
reduction in overall air emissions
from U.S. power plants. In addition
to rapid-response times, combined
cycle plants emit significantly fewer
emissions of carbon dioxide (CO2),
sulfur dioxides (SO2), nitrogen
oxides (Nox) and other air emissions.
CO2 emissions from power plants
using combined cycle technology are
about 50 percent lower than most
coal-fired plants. Emissions of NOx
and SO2 are 80 to 90 percent lower.
Combined cycle power plants
feature gas and steam turbines. The
gas turbine generates electricity
using natural gas, while the steam
turbine generates electricity using
waste heat from the gas turbine. The
process is highly efficient because the
exhaust heat, which would otherwise
be lost in the stack, is re-used in the
steam turbine to generate additional
electricity. The exhaust heat is sent
to a heat recovery steam generator
(HRSG), where the heat is absorbed
by heat exchanger tubes containing
second quarter of 2016. Last year,
the company began commercial
production at the 758-MW Panda
Sherman plant and the 758-MW
Temple plant in Texas.
What follows is a summary of four
modern power projects equipped
with CCGT technology.
Bechtel provided engineering,
procurement
and
construction
services for the project, which began
commercial production in July 2014.
Construction began in July 2012.
Equipped with advanced emissions
control technology, the Panda
Sherman plant is one of the cleanest
PANDA SHERMAN
power plants in the U.S., with carbon
monoxide emission less than 10
parts-per-million (ppm) and nitrogen
oxide emission less than 2.0 ppm.
“The plant’s advanced technology
enables the plant to produce higher
power output on higher temperature
days, which is important in this
region,” said Martin Tartibi, senior
vice president at Siemens Energy
Solutions Americas.
The plant can supply enough power
for 758,000 Texas homes.
The Panda Sherman plant uses
“Flex-Plant”
technology
from
Siemens. It’s the second Flex-Plant
in commercial operation in Texas.
Riviera Beach. Photo courtesy: Siemens
hot water to create steam for the
steam turbine.
One of the biggest developers
of combined cycle power plants
in the U.S. is Dallas-based Panda
Power Funds. The company recently
announced plans to build a third
combined cycle plant in Pennsylvania.
Panda Power Funds has two
Marcellus gas-fueled power plants
currently under construction in
Bradford and Lycoming counties.
The 829-MW Liberty power plant
is expected to begin commercial
operations in early 2016. The
829-MW Patriot power plant is
scheduled to begin operations in the
Built to support Texas’ vast amount
of wind power capacity, the 758-MW
Panda Sherman combined cycle
power plant is one of the fastest
starting power plants of its kind. The
combustion turbines provided by
Siemens Energy can begin producing
power in 10 minutes and can achieve
maximum power production in less
than 60 minutes. The fast ramping
capability allows power producer to
offset the loss of intermittent wind
power when the wind stops blowing.
Siemens provided the plant’s gas
turbines, steam turbine and waste
heat recovery boilers.
La Caridad. Photo courtesy: Siemens
Flex-Plants offer high efficiency and
operational f lexibility. Innovative
design features enable fast start and
fast ramping up and down across a
large operating window from low
plant turn-down to high plant output Each unit features an SGT65000F gas turbine. In addition to
the gas turbines, Siemens provided
one SST6-5000 steam turbine, two
SGen6-1000A generators, one SGen62000H generator, the SPPA-T3000
instrumentation and control system
as well as two Benson heavy ductfired heat recovery steam generators.
The gas turbines, steam turbines
and generators were manufactured
at the Siemens North American
manufacturing hub in Charlotte,
North Carolina. RIVIERA BEACH
In June 2011, the smokestacks of
the oil-fired Riviera Beach power
plant were demolished. In their
place, Florida Power & Light built
a more efficient plant fueled with
cleaner-burning natural gas.
The Riviera Beach Next Generation
Clean Energy Center in Florida began
commercial operation in April 2014.
The $1.3 billion project uses three
H-class gas turbines from Siemens.
Zachry Engineering was the EPC
contractor on this historic project.
The 1,250-MW combined cycle plant
produces enough power for 250,000
Florida homes.
The combined cycle plant is
expected to save FPL customers
hundreds of millions of dollars
over its 30-year lifetime. The
Riviera Beach facility is 33 percent
more fuel efficient than the plant
it replaced.
In addition, CO2
emissions are 50 percent lower and
NOx and SOx emissions are more
than 90 percent lower.
The same turbine used at Riviera
Beach set a world record for combined
cycle efficiency of 60.75 percent
in May 2011 at a power plant in
Bavaria, Germany. Siemens has sold
40 H-Class gas turbines worldwide.
Eleven are in commercial operation
with more than 100,000 equivalent
operating hours.
Siemens supplied three of its
SGT6-8000H gas turbines to the
Riviera Beach project, each delivering
an electrical generating capacity
of 274-MW. The plant entered
commercial operation on April 1.
LA CARIDAD
Minera Mexico, a subsidiary of
Grupo Mexico, the country’s largest
mining company and one of the
world’s largest copper producers,
wanted to produce most of its power
in-house. La Caridad I and II, a 500MW combined cycle plant in northern
Mexico, is part of the company’s plan
to generate 90 percent of its power
in-house.
The two 1x1 combined cycle units
feature two Siemens SGT6-5000F gas
turbines. The units are rated at 258.1
MW net output and 56.9 percent
efficiency. Siemens also provided the
steam turbines, air-cooled generators,
heat recovery steam generators and
the instrumentation and control
technology. Black & Veatch provided
engineering services for the project.
Unit I was commissioned in
September 2013 and Unit II was
commissioned in April 2014.
Producing its own power with
Siemens’ high-efficiency F-class
technology, the mining company will
be able to reduce its production costs.
The $580 million project allows the
company to cut its electricity costs by
40 percent to 6 cents per kWh. The
project also helps the state of Sonora
and the country by supplying reliable
power to the grid.
What’s more, it will allow the
company to reduce the cost of
producing copper to 89 cents a
pound, down from 93 cents.
The La Caridad I and II power
projects created more than 1,000 jobs
during construction and more than 50
direct jobs for day-to-day operation.
The plant produces about two thirds
of its electricity from the gas turbines.
The rest comes from exhaust heat
which then heats water to create vapor
that powers a second steam turbine.
By capturing the heat, 33 percent
additional electricity is produced.
NINEMILE 6
Entergy
Louisiana
completed
construction of Ninemile 6, a
560-MW combined cycle unit, in
December 2014. Built in Westwego
and serving New Orleans and
southeast Louisiana, it is the
first power plant the utility has
constructed in nearly 30 years.
The need for more generation
equipped with modern technologies
was critical. The retirement of Units 1
Ninemile 6. Photo courtesy: Entergy
and 2, the looming retirement of Unit 3,
and a growing economy created a crucial
need for replacement generation.
“Adding Ninemile 6 to our
portfolio gives us an opportunity to
meet that new need, while satisfying
our customers’ expectations of safe,
reliable and affordable energy,” said
Phillip May, president and chief
executive officer of Entergy Louisiana.
The new unit features dual-fuel
GE 7FA gas turbines, a heat recovery
steam generator from Vogt Power
International, and a steam turbine
from Toshiba. CB&I provided
engineering,
procurement
and
construction services for the project.
In addition to natural gas,
Ninemile 6 is equipped to burn
fuel oil, an important capability in
the event of a hurricane cutting off
supplies of natural gas. Without a
supply of gas, the plant can continue
producing power with fuel oil from
on-site tanks.
The unit was completed at a cost of
$655 million, well below its original
budget of $721 million.
The project employed 750 people
during construction and created
21 full time jobs for day-to-day
operation.
Eprinted and posted with permission to Siemens Energy from Power Engineering
March © 2015 PennWell Corporation