POWER May 2011 - 36

THE FUTURE OF COAL
Research and Development for
Future Coal Generation
If coal is to be a viable long-term fuel for a significant percentage of electricity
generation, research and development is needed to increase thermal efficiency,
demonstrate cost-effective and secure carbon dioxide capture and
storage, further improve emission controls, and reduce water demands.
By Dr. Andrew Maxson and Dr. Jeffrey Phillips, Electric Power Research Institute
C
oal-fired power plants currently supply
nearly half of the electricity consumed
worldwide. Globally, coal continues to
be the primary fuel for affordable and reliable
electric power production due to its low
cost and because many countries have indigenous
coal resources, which provide a level
of energy independence.
However, if coal-fired generation is to
remain a major source of electricity, it faces
significant economic and environmental challenges.
Although solutions to these challenges
are possible, much is unknown or untested.
Meeting the challenges of coal will require
research to improve existing technologies and
to develop new breakthrough technologies. It
will also require a commitment to an aggressive
schedule of technology development,
demonstration, and scale-up in a broad array
of design processes.
The Electric Power Research Institute
(EPRI) has proposed a strategy to meet future
global rising electricity demand by deploying
a " full portfolio " of clean energy technologies
(assuming a carbon-constrained future)
that simultaneously reduces pollutant emissions
and water use. This full portfolio includes
not only renewable energy resources,
end-use energy efficiency, advanced light water
reactor nuclear plants, and electric transportation,
but also advanced coal generation
with carbon capture and storage (CCS).
To capitalize on coal's advantages and
help mitigate its weaknesses, research and
development (R&D) needs to achieve the
following five key goals:
■ Improved plant efficiency, via high-temperature
materials and higher turbine inlet
temperatures.
■ Cost-effective, scalable CO2
new or retrofit applications.
.
capture, in
■ Environmentally safe and permanent storage
of CO2
■ Improved emission control systems, producing
near-zero emissions (NZE) of all
pollutants.
36
■ Advanced cooling and water management
methods to reduce water demand and pollutant
discharges.
Improving Efficiency
R&D to improve the thermodynamic efficiency
of coal power plants is a key part of
any strategy to make coal generation more
viable in the future. Increased efficiency,
produced by operating at higher steam temperatures,
reduces fuel costs and the amount
of CO2
generated per unit of plant output; a
9 percentage point efficiency gain results in a
20% reduction in CO2
emissions, as Figure 1
shows. Higher-efficiency plants can also have
better part-load operation and operating flexibility,
making lower emissions of other pollutants
possible and cutting balance-of-plant
costs, due to reduced size, water consumption,
and waste generation and consumables.
Currently, the majority of pulverized coal
(PC) plants in the U.S. are subcritical, with
an average efficiency of about 33% (based on
higher heating value [HHV]). Supercritical
plants, which typically operate at 3,600 psi
and temperatures up to 1,050F, provide significant
efficiency improvements over subcritical
units, achieving efficiencies of 38%
(HHV). Ultrasupercritical (USC) plants,
which have been in operation for years in
Europe and Japan, and more recently China,
have main steam conditions of 4,200 psi and
1,100F and generating efficiencies of up to
42% (HHV). In the U.S., the first new USC
PC plant, American Electric Power's (AEP's)
John W. Turk, Jr. Power Plant, is expected to
be commissioned in late 2012.
The primary technology advance needed
to enable construction of coal-fired boilers
and turbines with even higher efficiencies
is the development of metal alloys that retain
their strength at very high temperatures
and resist corrosion, creep, and other aging
mechanisms. These materials also must be
cost-effective to manufacture and fabricate
into boiler and turbine components.
Aggressive R&D programs for alloy
development and evaluation in Europe, Japan,
and the U.S. have identified ferritic
steels capable of meeting the duty require1.
Highs lead to lows. High-efficiency advanced pulverized coal power plants substantially
reduce fuel costs as well as CO2 and other emissions. (Efficiencies are based on higher
heating value.) Source: EPRI
9% Efficiency gain = 20% CO2 reduction
30
25
20
15
10
5
36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Net plant efficiency (%) (bituminous coal, without CO2 capture)
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POWER | May 2011
20% reduction in
CO2 corresponds to
similar reductions
(per MWh) in fuel
consumption,
emissions, and
water use
CO2 reduction (%)
Subcritical plant range
Commercial supercritical plant range
Advanced ultrasupercritical plant range
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POWER May 2011

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