POWER December 2021 - 32

COAL POWER
Unit Flexibility and Asset
Optimization: Helping Coal-Fired
Power Plants Survive in a
Renewables-Driven Market
Many coal-fired power plants are being asked to ramp output up and down regularly,
and often to levels less than units were originally designed to operate at. Implementing
a Unit Flexibility and Asset Optimization program can help plants widen operating
windows and hit necessary targets.
Bruce Ogden
C
urrent market
conditions,
political
pressures, and environmental
compliance burdens have greatly
reduced the amount of power that coalfired
plants produce annually. However,
the greatest impact to coal-fired plants
has been the resurgence of the American
natural gas market, thus providing an
abundant and cheap source of a cleaner
burning fuel. Couple this with the growing
impact of renewable energy resources,
such as wind and solar power, and it's
easy to understand why many coal-fired
plants are struggling to stay in operation.
Survival of coal-fired power plants
demands that managers adapt and reinvent
their industry. Units must be able
to provide cheap, reliable, baseload
power, while also being able to follow
the frequent changes in power output
caused by intermittent renewable power
sources. Improving unit flexibility and optimizing
assets are great first steps for
coal-fired power producers.
Most coal-fired plants were originally
designed to operate at full load from outage
to outage. With the large increase of
" take or pay " renewable contracts, many
of the formerly baseload plants are finding
that they are producing excess MWs
and at a price where they are losing money.
For coal-fired plants that participate
in competitive markets, they can experience
negative Locational Marginal Pricing
(LMP), which means for every MW they
produce that the independent system operator
(ISO) or regional transmission organization
(RTO) doesn't need or want, the
power producer can be penalized.
For example, if a 1000-MW plant's
LMP goes to -$200 and the plant only
has a 50% turndown, the plant will be
32
penalized $200/MWh for 500 MW of
output or $100,000/hr (Table 1). The other
option is for the plant to shut down
to avoid the penalty. However, this can
create extreme operations and maintenance
(O&M) impacts, as the negative
LMP issue could occur daily, or at least
LMP
MW $ Loss/hr
$0 $500
-$10 $500
-$25 $500
-$50 $500
-$100 $500
$7,500
-$5,000
-$12,500
-$25,000
$ Loss/day
$180,000
-$120,000
-$300,000
-$600,000
-$50,000 -$1,200,000
-$200 $500 -$100,000 -$2,400,000
50% Load
$0 $250
-$10 $250
-$25 $250
-$50 $250
-$100 $250
-$200 $250
$0 $100
-$10 $100
-$25 $100
-$50 $100
-$100 $100
-$200 $100
Table 1.
$3,750
-$2,500
-$6,250
-$12,500
-$25,000
20% Load
$1,500
-$1,000
-$2,500
-$5,000
-$10,000
-$20,000
$36,000
-$24,000
-$60,000
-$120,000
-$240,000
-$480,000
This table shows the theoretical
economic impact experienced by a 500-MW
coal-fired power plant with a margin operating
price of $15/MWh when negative Locational
Marginal Pricing (LMP) occurs in its market.
The savings is substantial when unit output
can be reduced to 20% rather than 50%.
Source: EAPC Industrial Services
www.powermag.com
$90,000
-$60,000
-$150,000
-$300,000
-$600,000
-$50,000 -$1,200,000
weekly. When a plant is voluntarily taken
out of service upon the request from the
ISO/RTO, the ISO/RTO then determines
when the plant can come back into service.
That could be a day, a week, or even
a month later in extreme cases.
Unit Flexibility and Asset
Optimization Program
A Unit Flexibility and Asset Optimization
program is concentrated in the following
two key areas:
■ Low-Load Operation Optimization.
Operate the unit at the lowest, safe
and stable load while maintaining the
highest heat rate, meeting all environmental
limits, limiting O&M impacts
by leaving the unit online, and
avoiding all cycling. This increases the
unit's marketability in the day-ahead
market, as the unit is subsequently
able to operate over a much larger
load range, can respond to sudden
changes in renewable energy output,
and provides improved grid stability
during system upsets.
■ Ramp Rate Improvement. Substantially
increase the unit ramp rate up to a
range of 10-15 MW/minute or higher.
This allows the unit to respond to
sudden changes in renewable power
output, capture periods of increased
power prices, and increases the unit's
marketability in the day-ahead market.
When implementing a Unit Flexibility
and Asset Optimization program, some
common goals include:
■ Achieve the lowest possible load and
the fastest ramp rate with a concentration
on low-hanging fruit.
POWER | December 2021
http://www.powermag.com
POWER December 2021

Table of Contents for the Digital Edition of POWER December 2021
