pwr_july-2024 - 18

REINVENTION AWARD
Morrow Reinvented: HL-Class
Gas Turbine Powers a Coal Plant's
Rebirth
Courtesy: Cooperative Energy
The Morrow Repower Project, winner of POWER's 2024 Reinvention Award,
exemplified a strategic coal-to-gas conversion at a brownfield site that masterfully
combined cutting-edge advanced technology with a commitment to financial and
community stewardship.
Sonal Patel
C
ooperative Energy is a generation
and transmission electric co-op
headquartered in Hattiesburg, Mississippi,
that serves 11 small distribution
cooperatives spanning from the Mississippi
Delta to the Gulf Coast. It operates
under a member-owned not-for-profit
model, providing power and emergency
contingencies to more than 448,000
members in 55 of Mississippi's 82 counties.
About a decade ago, it began contemplating
the future of its fleet.
In 2012, the co-op joined the Midcontinent
Independent System Operator
(MISO) as one portion of the regional
transmission operator's larger balancing
authority, allowing it to leverage low-cost
energy purchasing while finding new avenues
for its own generation. As with all
of Cooperative Energy's efforts, the measure
was firmly embedded in its larger imperative
to produce affordable and reliable
power consistently. But it also sought to
provide overall market transparency as
stringent new environmental regulations
and technological advancements transformed
the market dramatically.
A particular concern rested on the future
of the R.D. Morrow Sr. Generating
Station, a 400-MW two-unit coal-fired facility
Cooperative Energy opened in 1978.
While the co-op had begun exploring repowering
the landmark plant with natural
gas as far back as 2013, given uncertainties
about the future of coal power, by
2016, decisive action became critical.
" It really came down to economics, "
18
Mark Smith, Cooperative Energy's senior
vice president of Power Generation, told
POWER. " We had an approximately 3%
capacity factor on coal. The units could
not compete in the MISO market due to
the cost of operation, as well as flexibility
on the unit during operation. "
Along with the prospect of continuously
complying with ever-more stringent
environmental rules, the plant
grappled with high costs to transport its
coal 440 miles to the site. To keep the
plant viable over the long term, Cooperative
was deeply aware it would need to
" spend some big money, " Smith said.
In 2016, Cooperative's generation planning
group began an expansive year-long
study to explore its power supply options.
" It's something we do periodically to evaluate
our fleet and determine the most
cost-effective way to serve our members, "
said Trey Cannon, director of Generation
Projects with Cooperative Energy.
The study suggested a repower project at
Morrow was the best way forward.
" There were a number of reasons, "
Cannon noted. " We had several assets
there that were in good shape and feasible
for reuse, " such as the switchyard, the
transmission system, circulating water
systems, and the powerhouse. " And then
maybe most specifically, just the size of
the steam turbines themselves were very
well suited to power a very large gas turbine
that's very efficient, " he said.
After a Burns & McDonnell study
showed that repowering presented potential
cost savings of between 25% and
www.powermag.com
35%, Cooperative moved quickly. In June
2018, the co-op's board cemented a decision
to retire the original two-unit plant
and replace it under a five-year ambitious
conversion plan with an advanced-class
natural gas unit.
The 572-MW Morrow Repower project
began commercial operation in March
2023. Powered by a 60-Hz Siemens Energy
SGT6-9000HL paired with an existing
steam turbine, the unique baseload
plant is today a reliability powerhouse
controlled and dispatched by MISO.
A Rigorous Technology Selection
As a crucial first step, the co-op set out
to explore-with an " open mind " -its
large heavy-duty gas turbine options,
carefully weighing choices from three
major gas turbine manufacturers that
were then available. " We would take the
performance guarantees from each of the
three different gas turbine vendors, and
we would run them against current production
cost models and determine their
economic [potential] based on future gas
pricing and future power costs and things
of that nature, " Smith noted. Siemens
Energy's SGT6-9000HL routinely ranked
high in flexibility attributes, including for
start time, ramp rate, and turndown of the
unit, as well as in efficiency, Smith said.
However, the decision to order the
technology was not without significant
risk. When Cooperative was mulling its
options in 2018, Siemens Energy had
freshly unveiled the HL-class-its largest,
most powerful, and most efficient
POWER | July 2024
http://www.powermag.com
pwr_july-2024

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