POWER November 2020 - 20

RESEARCH & DEVELOPMENT
NETL: Meeting the Needs of the
Nation's Fossil Power Plant Fleet
Through programs such as Transformative Power Generation, High-Performance
Materials, and Advanced Coal Processing, the National Energy Technology Laboratory
(NETL) is conducting research and development (R&D) to enable the nation's fleet
of coal and natural gas power plants to operate in a flexible, efficient, and reliable
manner, while reducing operation and maintenance costs.
Briggs White and Conor Griffith
A
lthough the country has a diverse
energy portfolio, including nuclear
power and a growing renewables
sector, fossil power plants still supply a
majority of the nation's electricity. However,
these facilities are aging. Most coal
plants are 35 to 55 years old, with many
even older. Additionally, the natural gas
combined cycle (NGCC) fleet, which provides
significant flexible capacity services
to the grid, has many plants that are
15 to 20 years old, and some have been
in operation for 25 to 35 years (Figure 1).
Both classes of assets will be required
to operate more flexibly than when they
were originally built, raising challenges
with respect to materials reliability and efficiency.
Forced outage rates have been
increasing as these plants age and cycle
more to balance load, driven by increased
variable renewable generation on the grid.
" More and more, the grid is calling on
fossil resources to provide energy in a way
that requires plants to ramp up quickly and
then ramp back down. These plants were
never designed to operate that way, " NETL
Technology Manager for High-Performance
Materials research Briggs White explained.
" When the plants aren't dispatching, they
aren't in the money and are typically turned
off or idled at minimum load. All this ramping
causes damage to the plant and they
don't generate revenue. "
Addressing Reliability Through
Superior Materials
NETL analyzed data from the North American
Electric Reliability Corp. (NERC) to
determine the key sources of forced outages
in coal and gas plants. The data was
sourced from the U.S. fleet of coal and
NGCC plants from 2013 to 2017. The analysis
found that within coal plants, boilers
are a key cause of frequent failure. As
much as 54% of the forced fleet outages
were caused by issues with the boiler,
with waterwall issues responsible for as
20
1. This graph shows the commercial online years of currently operating coal-fired and natural
gas combined cycle (NGCC) units in the U.S. Source: National Energy Technology Laboratory
much as 40% of boiler-related outages.
In total, boiler plus steam turbine components
within coal plants caused 70% of
the forced outages. For gas plants, there
are similar components in heat recovery
steam generators (HRSGs), and steam
turbines drive failures as well.
NETL assessed the specific failing
components within these subsystems
to determine a cause. It found that pipes
and other surfaces were failing from a
combination of fatigue failure from cycling,
and erosion and corrosion from
opportunity fuels and oxide spallation.
Components made from more robust
materials seemed to present solutions.
To address these challenges, the U.S.
Department of Energy's (DOE's) HighPerformance
Materials program competitively
awarded $10 million in funds
to General Electric (GE) to support the
development of materials to address
thermal fatigue and corrosion, two of
the leading causes of damage to steam
cycle components inside power plants.
In one of the projects, NETL is working
with Edison Welding Institute and Manufacturing
Technology Inc. along with GE to
improve the durability of dissimilar metal
welds (DMWs) for boiler and HRSG applications.
This will enhance erosion and
oxidation resistance in high-temperature
steam for high-pressure turbine blades
inside the existing steam-powered fleet.
The goal of this work is to reduce maintewww.powermag.com
nance
costs while enhancing the capability
of coal plant cycling operations.
NETL and GE are also developing costeffective
weld overlay compositions for
boiler tubing and multi-layered coatings
that deliver improved resistance against
erosion and oxidation in turbine blades under
high-pressure steam conditions. Other
goals of this improved materials project
include increasing the time between outages
for both boilers and turbines while
also eliminating or significantly reducing
the nickel content in weld overlay, which
will mitigate costs. These advanced coatings
could decrease power plant component
cost, increase performance, and
extend time between outages.
Beyond these two projects with GE,
NETL is collaborating with partners to
develop additional manufacturing technologies
capable of robust DMWs, either
through additive manufacturing of
joints with graded compositions, solidstate
processing, or advanced welding.
In addition, NETL is investing in data
analytics approaches for predicting when
components will fail, informed by materials
models and process data.
Addressing outages is a crucial priority
for NETL, especially as units age.
When looking at demographics, the existing
fleet is dominated by older subcritical
units that are performing increasing
amounts of cycling, which results in
increased
equivalent
forced
outages
POWER | November 2020

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POWER November 2020

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