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March 2013 www.power-eng.com
EMISSIONS CONTROLUNDERSTANDING YOUR OPTIONS
HYDROPOWERTHE POWER OF REHABILITATION
PRB COALCHALLENGES AND SOLUTIONS
themagazine of power generation
Wind TurbineTECHNOLOGYCHOICES
NHASp
ecial
dvertis
ingSe
ction35
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t e magazine of power generat on
117YEARS
-
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March 2013 www.power-eng.com
EMISSIONS CONTROLUNDERSTANDING YOUR OPTIONS
HYDROPOWERTHE POWER OF REHABILITATION
PRB COALCHALLENGES AND SOLUTIONS
NHASp
ecial
dvertis
ingSe
ction35
-47
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Power Engineering
CORPORATE HEADQUARTERSPennWell Corp.1421 South Sheridan Road Tulsa, OK 74112
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NH
FEATURESNo. 3, March 2013
117VOLUME
DEPARTMENTS 2 Opinion 6 Clearing the Air 8 View on Renewables10 Industry Watch12 Nuclear Reactions14 What Works60 Ad Index
35 The Hydropower Industry sPursuit of Excellence
inda hurch- iocci, executive director o the National Hydropothe state of the hydropower industry and the potential for addin
48 PRB Coal:Material HandlingChallenges and Solutions
More coal-red power producers are turning to coal fromWyomings Powder River Basin because its cleaner-burning and low in sulfur content. But converting a plantto burn PRB coal comes with many challenges.
42 When Budgeting for 316(b)Comp iance, Consi er A Options
Section 316(b) under the Clean Water Act is scheduled to be nalized in
June. The new rule will establish new requirements for cooling water intakestructures at existing power plants. What do power producers need to knowto comply? Well tell you.
28 Moving ForwardCoal-red power plants across the U.S. are being equipped with emissioncontrols to limit nitrogen oxides, sulfur oxides, soot and mercury. PowerEngineering examines the options available to power producers.
36 Squeezing More Powerfrom Hydroelectric Plants
Many U.S. hydropower plants are more than 50 years old and in needof rehabilitation. They represent a phenomenal opportunity to increasethe production of renewable energy in the U.S.Power Engineeringexamines the rehabilitation of three hydropower projects in the U.S.
22The (Lost) Art of WindTurbine Technology Selection
Not all wind turbines are created equal. They vary in size,performance, cost, reliability and appearance. There arestrategies for choosing the best technology. Aaron Andersonof Burns & McDonnell explains.
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OPINION
To her credit, McCarthy was instru-
mental in lowering the cost of comply-
ing with the Mercury Air and Toxics
Standard, which was nalized and en-
acted into law last year. The nal rule
was more exible than the initial pro-
posal and required fewer plants to in-
stall costly emission control equipment.
But her selection means the EPA willbe working hard to nalize the rst
greenhouse gas standard for power
plants, a standard that precludes the
construction of new, cleaner-burning
coal-red plants and discourages invest-
ment in clean coal technologies. It also
means the EPA will be expanding its
anti-coal agenda by proposing a green-
house gas standard that targets existing
coal-red power plants.
McCarthy delivered a compelling
speech at COAL-GEN last August in
Louisville, Ky. As compelling as it was,
her message was carefully crafted and
failed to trump the chief criticisms of the
EPAs blitz of new emission standards,
which fail to achieve balance between
economic concerns and environmental
concerns.
Here are a couple of excerpts from Mc-
Carthys speech last August.
McCarthy: My job is primarily to
implement the Clean Air Act. Our Clean
Air Act is prescriptive, but it does allow
exibility. It looks at variability in tech-
nology and design. It is not a law that
picks winners and losers.
Not exactly.
In the battle between coal-red and
gas-red generation, gas is clearly win-
ning due partly to low-priced natural
gas. But gas has received a lot of help
from the EPA. Instead of embracing
competition and technology to deter-
mine the winner, the EPA is picking the
Shes a plain-spoken Bostonian
who is popular with environ-
mental groups and even some in
the energy industry.
She was one of our keynote speak-
ers at COAL-GEN 2012, and she has
won my begrudging admiration for her
straight-talking discourse with the pow-
er generation industry.At the time this column was written,
Gina McCarthy was being widely exalt-
ed as President Obamas pick to lead the
U.S. Environmental Protection Agency.
Her selection is by no means a prologue
for diplomacy or compromise with the
U.S. power sector. Her selection signies
a commitment to a calculated strategy
to advance the administrations War on
Coal, a conict borne from real rule-
makings and real policies carried out by
the EPAs previous administrator, Lisa
Jackson, who left the agencys top post
last month.
The changing of the guard will have
little effect on the EPAs anti-coal agen-
da. McCarthy, a former state regulator
from Connecticut and assistant admin-
istrator of the EPAs Ofce of Air and
Radiation, has led the EPAs efforts to
impose a suite of new clean-air rules for
U.S. power plants, including a green-
house gas standard that effectively bars
the construction of new, highly efcient
coal-red generation in the U.S.
Given Obamas State of the Union Ad-
dress, where he pledged to make climate
change a priority and threatened ex-
ecutive action in the absence of climate-
change legislation, McCarthys selection
shouldnt be a surprise. She is a veteran
regulator and a clean-air expert who has
faced heated criticism from lawmakers
and industry leaders for the agencys
tough new emission standards.
winner by managing the competitive-
ness of coal with new regulation that
favors gas over coal. The EPAs proposed
New Source Performance Standard is a
perfect example.
McCarthy: The Clean Air Act recog-
nizes that coal is a signicant and ma-
jor source of electricity generation. We
do not anticipate that the rules we haveput into place or are proposing will do
anything to change that fact. We believe
that as a result of our rules, clean coal
will have a place in the future.
This is disingenuous at best.
The prospects and the economics of
building a modern-day coal-red power
plant equipped with clean-coal technol-
ogy in the U.S. have been severely dam-
aged by the EPAs proposed NSPS, which
is expected to be nalized this year.
Without it, the industry would undoubt-
edly be pursuing clean coal projects to
mitigate the risk associated with the un-
ruly price of natural gas.
McCarthys nomination will be met
with erce opposition from Republican
senators. Already, some groups are urg-
ing lawmakers to reject the nomination.
She will face tough questions about al-
legations the EPA has exceeded its statu-
tory authority and has collaborated with
radical environmental groups to settle
enforcement lawsuits.
If McCarthy is conrmed, Obama
will have a capable general to contin-
ue the administrations assault on the
nations most important segment of
the power sector. If she is successful, it
will fur ther handicap the power sec-
tors effort to meet demand with this
nations abundant supply of reliably-
priced coal and make a mockery of
Obamas so-called all-of-the-above
energy strategy.
A Contentious PickBY RUSSELL RAY, MANAGING EDITOR
Gina McCarthy
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Powerplant EngineeringDESIGN & EPC CONSTRUCTIONSERVICES:
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CLEARING THE AIR
given their own numeric limits.
Startup emissions must be includ-
ed in dispersion modeling and can
be problematic for short-term Na-
tional Ambient Air Quality Standards
(NAAQS) such as one-hour nitrogendioxide (NO
2). One modeling solution
is to account for the fact that during a
single hour of operation, startup emis-
sions might occur for 20 minutes with
the rest of the hour at the controlled
emission rate. This will result in a lower
modeled pound per hour than assum-
ing startup lasts for a full hour. A longer
startup time in the permit will increase
operational exibility but will make the
modeling results higher.
A construction permit may set limits
on the number of starts per year, but
care should be taken to avoid limits on
starts per day unless absolutely neces-
sary. Annual potential emissions of CO2
will often represent a greater percentage
of the Prevention of Signicant Deterio-
ration (PSD) major project thresholds
than will be the case for other pollut-
ants. If a source wanted to remain below
major source thresholds, CO2
emissions
would then decide the operating hour
permit limit.
The key to successful permitting and
exible operation is upfront consulta-
tion with the permitting agency to en-
sure that they understand how the plant
will be dispatched (base load, wind-fol-
lowing, seasonal). Permit limits should
provide a level of margin above manu-
facturer guarantees regarding emission
limits and startup durations. A good
permit will keep your plant running
smoothly.
Time is money when starting a
resource to meet load demand.
Startup emission rates, howev-
er, can greatly exceed steady-state emis-
sion rates and they can pose a hurdle in
the permitting, as well as the compli-ance, of a facility.
With the growth of intermittent re-
sources such as wind and solar, gas tur-
bine and heat recovery steam generator
(HRSG) manufactures are designing for
faster starts and improved operational
exibility. These improvements increase
their viability for responding to energy
uctuations in the market and promote
grid stability. Being online and selling
energy or capacity has several economic
advantages. Reducing startup emissions
are a benet as well; to the tune of 30%
reduced greenhouse gas emissions com-
pared to a traditionally designed com-
bined cycle plant, according to some
manufacturers.
Traditionally designed combined
cycle facilities are limited by stresses
imposed on steam generation equip-
ment due to high thermal transients in
the bottoming cycle. The gas turbine is
ramped to a low-load hold point to al-
low the cycle to safely reach its ideal
steam conditions before eventually
making its way to full load capability.
Recently, HRSG have been designed
with thinner walled drums to reduce
the time required to meet these condi-
tions. While this results in much faster
ramp rates, it is still slower than the
capability of a once-through steam gen-
erator (OTSG).
OTSG designs either remove all
drums from a traditional HRSG or
replace the high pressure drum with
a thin walled separator, allowing for
maximized gas turbine ramping. To
accommodate the fast start of the gas
turbine, steam is initially bypassed to
the condenser as the steam turbine andpiping are safely warmed. To minimize
startup time, these facilities also include
an auxiliary boiler to keep the steam
turbine seal system and attemperation
system warm to avoid thermal shock.
Taken together, all of these features re-
sult in fast energy to the grid and signi-
cantly reduced startup emissions.
Traditional combined cycle plants
have various startup times depending
on the duration of the shutdown. In
other words, startup time is a function
of the cooling which has occurred in
the cycle. Depending on the congu-
ration, a traditional startup can range
anywhere from 90 minutes to four
hours. The integration of fast start fea-
tures can reduce startup times by up to
50 percent. It is commonplace in the
industry for simple cycle gas turbines
to achieve a start cycle in 10 minutes,
regardless of the amount of time it has
been shut down. Similarly, reciprocat-
ing engines are capable of reaching full
load in as little as ve minutes (but are
sometimes permitted for startup times
of 10 to 30 minutes).
Permitting of startup conditions re-
quires a special balance between real-
ity and operating margin. Emissions
during startup and shutdown are not
excluded from Best Available Control
Technology (BACT) limits but are usu-
ally evaluated as a separate operating
scenario from full load operation and
Protecting YourPlants Zero to 60BY ROBYNN ANDRACSEK, P.E., BURNS & MCDONNELL AND CONTRIBUTING EDITOR, AND NICK BAUER, P.E., BURNS & MCDONNELL
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316(b) COMPLIANCE:CONSIDER ALL OPTIONS
Utility managers using once-through cooling are concerned about how they will comply with the new 316(b)
cooling water rules. ENERCON has worked with the industry for decades to nd practical, cost effective
solutions to regulatory mandates. We are the industry leader in evaluation of retrot cooling system
alternatives, providing complete solutions that meet state and federal regulations.
ENERCON provides complete services, including technology evaluation, ecological services, cooling system
design, cost-benet analyses, large component and plant siting, thermal discharge solutions, regulatory
negotiations, permitting, and environmental compliance. www.enercon.com
Corporate Headquarters:Atlanta. Other locations: Ann Arbor, Baton Rouge, Birmingham, Chicago, Dallas, Denver, Duluth, GA, Germantown, MD,
Houston, Humble, TX, Kansas City, Northern New Jersey, Oakland, Oak Ridge, Oklahoma City, Orlando, Pittsburgh, Sacramento, San Clemente, Tampa,
Tulsa, Washington, DC. International:Abu Dhabi, Belgium.enercon.com/locationsfor details.
316(b) COMPLIANCE:CONSIDER ALL OPTIONS
ENERCON HAS PRACTICAL SOLUTIONS.
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VIEW ON RENEWABLES
money on customer acquisition and re-
tention. But utilities that are active in de-
regulated markets can create substantial
customer loyalty by enrolling custom-
ers in solar leases and PPAs. With solar
nancing, utilities create a 20-year con-
tracted electricity supply arrangement
that can dramatically decrease their cus-tomer turnover. Homeowners would also
be more likely to adopt solar if utilities
were nancing the systems.
A GOLDEN OPPORTUNITYTo recap: utilities have large tax appe-
tites, which can be fed by attractive tax
credits for solar systems; they know about
owning energy assets and selling power
to customers; and they struggle with cus-
tomer retention - a struggle that can be
alleviated by locking customers into 20-
to 25-year contracts. This is true for both
regulated and deregulated utilities: for
regulated utilities, solar is an investment
opportunity they can pursue outside
their regulated service territory.
Solar will play a larger role in our en-
ergy mix. Utilities should start thinking
about participating in residential solar
now to evolve with the growing industry.
Residential solar is a maturing asset class
with high returns and low default rates
that affords utilities the chance to put bil-
lions of dollars of capital to work.
Solar is not a niche industry. Assum-
ing todays best-in-class installation
costs and a reasonable cost of capital,
there is $60 billion per year of home-
owner electricity payments that could be
renanced at a savings with a solar lease
or PPA. This is an enormous, largely un-
tapped market where there are big prof-
its to be made, and utilities are ideally
positioned to reap them.
More utilities are beginning to
recognize the benets of in-
vesting in residential solar -
nancing. Although some utilities regard
residential solar as a threat to their busi-
nesses, what they should be looking at is
the prot opportunity. Heres why.
THIRD-PARTY OWNEDRESIDENTIAL SOLAR
Third-party nancing has made resi-
dential solar a mass-market service. In
2007, a handful of companies started
selling solar leases and power purchase
agreements to consumers. Instead of sell-
ing solar as hardware, they sold solar as
a service. With solar as a service, a third
party owns and installs the hardware and
agrees to maintain, insure and monitor it
as needed during a 20-25 year contract.
The homeowner can either pay the sys-
tem owner a monthly fee for use of the
solar equipment, or pay monthly for
the electricity generated by the system.
Homeowners with disposable income
also have the option of paying up front
for all the power the system will generate
during the contract term. More Ameri-
cans are going solar each year. About 80
percent prefer solar nancing products to
cash purchases.
TAX APPETITES: HUNGRY,HUNGRY UTILITIES
U.S. utilities are generally highly prot-
able enterprises with signicant incomes.
This means they pay a lot of taxes. To alle-
viate their large tax burdens, utilities look
for tax credits put in place by the federal
government to encourage investment.
Companies that benet from tax credits
are said to have large tax appetites. Util-
ity holding companies in the U.S. tend to
have big tax appetites.
The idea of tax credits is central to the
U.S. solar industry. If a company buys
a solar system, the federal government
grants it a tax credit for 30 percent of the
systems total cost. The tax credit, known
as the federal investment tax credit, helps
sate utilities large tax appetites. The 30percent ITC is effective until Dec. 31,
2015, at which point it decreases to 10
percent. Ten percent is unlikely to attract
as much interest, but until 2016, were liv-
ing in an ITC world with a lot of potential
tax equity from utilities.
DOING WHAT THEY DO BESTThird-party owned residential solar is
a natural evolution for utilities. Unlike
other third-party solar investors, utilities
have expertise in owning and maintain-
ing power generation assets and selling
power to millions of homeowners. This
expertise gives utilities a leg up on other
investors interested in solar assets.
Solar is also an effective solution to a
problem utilities selling power in deregu-
lated markets face: customer churn. Utili-
ties with large numbers of deregulated
customers typically experience high cus-
tomer turnover. In fact, the typical cus-
tomer in a deregulated market can rotate
through electricity providers as often as
once every nine months. Investments in
third-party nanced residential solar are
a tool utilities can use to acquire and re-
tain unregulated customers.
Take, as an example, a large retail elec-
tricity provider, owned by a utility hold-
ing company, based in the eastern U.S.,
that serves millions of customers. The
customers have options about where
to buy their electricity, which forces the
utility to spend signicant amounts of
Utilities and ResidentialSolar Financing:
A Golden OpportunityBY KRISTIAN HANELT, SVP RENEWABLE CAPITAL MARKETS, CLEAN POWER FINANCE
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ENERGY UNDERSTOOD
Brandon Shores AQCS Retrofit, Baltimore, MD
E N E R G Y
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The changing energy environment makes decision-making challenging.We cant predict the future, but we have tools that can help. For example,
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GAS GENERATION
and maintain reliable and affordable ser-
vice to consumers. But there are actions
the federal government can and should
take to help:
1. The EPA should recognize the threat
posed to electric reliability and use
more of their authority to provide
utilities that need it with additionaltime to comply with their newest re-
quirements without subjecting them
to civil or criminal penalties.
2. The Federal Energy Regulatory
Commission (FERC) has conducted
a series of helpful technical confer-
ences to look at certain issues such
as gas/electric day coordination, but
the agency should do more to spur
and expedite approval and construc-
tion of new natural gas pipelines.
3. In its ongoing deliberations over
budgets and tax reform, Congress
should preserve utilities access to
capital on affordable terms. For
public power utilities, that means
retaining the full exemption from
income tax for interest paid on state
and municipal bonds.
4. Congress should pass legislation
similar to that by U.S. Rep. Pete Ol-
son, (R-Texas) that would protect
utilities complying with emergency
orders from FERC or the Depart-
ment of Energy to operate certain
generators for reliability purposes
from also incurring penalties by EPA
if operating the generators during
that period results in violation of
EPA rules.
Working together, and with federal
assistance, we can avert major prob-
lems and move to a more modern and
cleaner electric generation eet. But we
must act quickly.
Industry groups, regulators, legisla-
tors, think tanks, vendors and others
have been discussing this convergence for
months. The discussion has centered on
issues such as inter-industry communi-
cation, business practices, scheduling of
gas deliveries and curtailment policies in
recognition of the cultural differencesbetween the two industries.
While those are important matters
to resolve, more emphasis needs to be
placed quickly on building the necessary
infrastructure in time. This includes the
retrots to existing coal-red plants and
the new gas-red plants that are needed,
but even more importantly it includes the
natural gas pipelines and storage facilities
required to make it all work.
Electric generators essentially have un-
til 2016 - three years from now - to com-
ply with the newest EPA requirements.
Hundreds of power plants are involved.
The regional electric grid operator, the
Midwest Independent System Operator,
has expressed concern about the poten-
tial impact on electric reliability and is
busy working with the regional utilities
to coordinate and sequence activities
in order to maintain service. But there
is real concern as to whether all of the
necessary pipelines and storage facilities
can be built in time. It often takes about
four years to gain the approvals and con-
struct a new pipeline, although the time
will vary depending on the specics and
length of the route. New natural gas stor-
age sites require certain geologic and oth-
er criteria that are not available in many
locations, and they also can take several
years to permit and construct even when
a suitable location is identied.
Industry is doing its part to implement
these changes, build the infrastructure
Whether you call it interde-
pendence, harmonization,
coordination, chaos, or
something else, much of the electricity
industry is appropriately focused on the
increased use of natural gas to generate
electricity and the related issues that need
to be addressed for that change to happenin a cost-effective and reliable manner for
both sectors. The increased use of natural
gas to generate electricity is occurring for
several reasons: 1) the cost of complying
with Environmental Protection Agency
(EPA) regulations for many existing coal-
red power plants; 2) the inability to
build new coal-red power plants in the
near term due to EPA requirements on
emissions of greenhouse gases; 3) the low
cost and apparent abundance of natural
gas; and 4) the need for additional gen-
eration capability to back up highly vari-
able sources such as wind and solar.
Demand for natural gas is also pro-
jected to quickly increase in the manu-
facturing sector. A recent report prepared
by Dow Chemical based on public an-
nouncements by numerous corporations
shows new, near term investment in
manufacturing of $80 billion, accompa-
nied by an increase in natural gas con-
sumption of 6 Bcf per day. These invest-
ments also mean increased demand for
electricity, most of which will be gener-
ated using gas. The real kicker in this
rapidly unfolding scenario is that most of
the affected electric generation facilities,
as well as a substantial amount of the in-
crease in manufacturing, is happening in
one region of the country the Midwest
and in the next three to four years. Other
regions, notably New England, are seri-
ously challenged too, but the heartland is
where it is all converging.
So Much to Build So Little TimeBY JOE NIPPER, SENIOR VICE PRESIDENT, GOVERNMENT RELATIONS, AMERICAN PUBLIC POWER ASSOCIATION
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CAT, CATERPILLAR, their respective logos, ACERT, Caterpillar Yellow, the Power Edge trade dress, as well as corporate and product
identity used herein, are trademarks of Caterpillar and may not be used without permission. 2013 Caterpillar. All Rights Reserved.
POSSIBLEBecause of CatGas Power Systems
Without any access to power, Mtwara and Lindi, in Tanzania, Africa, turned to
Wentworth Resources Limited and Caterpillar. The answer was a gas-to-power
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NUCLEAR REACTIONS
announced plans to close the Kewaunee
nuclear plant in Wisconsin in 2013,
placing part of the blame on competi-
tion with gas-red electricity. Dominion
made a point to emphasize that the deci-
sion was not related to poor station per-
formance but on economics. The plants
power purchase agreements were ending
at a time of projected low wholesale elec-tricity prices in the region due primarily
to low natural gas prices rendering con-
tinued operation uneconomic.
One UBS Securities analyst called the
current low-price environment a key fac-
tor in putting a projected 2,000 to 3,000
MW of nuclear capacity at risk. The ana-
lyst said that while the variable costs of
nuclear plant dispatch remain low, tight
margins in a gas-driven market cannot
support the high xed cost of certain nu-
clear assets. With xed costs for nuclear
plants four to ve times those for a com-
parable coal plant, maintenance costs of
about $50/kW-year and rising fuel costs,
the economic viability of merchant nu-
clear generators may decline.
FUKUSHIMA VULNERABILITIESDespite all weve learned over the past
two years about the Fukushima Daiichi
accident, the full nancial impact of the
incident on U.S. nuclear plants is not yet
clear. Plants have taken a number of steps
on their own, particularly with respect
to the availability of portable emergency
equipment to enhance their ability to re-
spond to a loss-of-cooling-capability situ-
ation. Whether these steps are enough to
satisfy potential regulatory requirements,
however, has not been answered.
Another open issue emerging from Fu-
kushima is whether ltered vents will be
mandated for certain boiling water reac-
tor designs. This hardware can enhance
To be or not to be, that is the ques-
tion. OK, maybe Shakespeare is a
bit dramatic for a nuclear energy
column, but bear with me.
All power plants face challenges. Most
are relatively modest trimming operat-
ing and maintenance budgets, allocating
capital to a persistent equipment issue
or responding to new regulations. Occa-sionally, however, some can reach exis-
tential levels; that is, challenges that im-
peril a plants continued viability.
The U.S. nuclear industr y faces
at least three such threats this year.
While the nal outcome is uncertain,
I wouldnt necessarily be surprised
if multiple nuclear plant owners an-
nounced decisions this year to shut
plants down in the next few years.
The three main threats confronting
U.S. nuclear plant owners are the low
price of natural gas, potential plant
and equipment upgrades to address
vulnerabilit ies exposed by Fukushima
and possible nuclear plant require-
ments associated with seismic haz-
ards. Each of these threats could im-
pose economic pressures that put the
assets continued viability at r isk.
NATURAL GAS PRICESThe low price of natural gas in the
U.S. puts particular pressure on mer-
chant generating assets. The impact has
been felt most severely by merchant coal
plants, many of which are now slated for
closure in coming years because they can-
not compete on the margin with gas-red
plants , especially when factoring in addi-
tional capital outlays required to comply
with pending environmental regulations.
Somewhat surprisingly, merchant
nuclear plants are now in the proverbial
crosshairs. In October 2012, Dominion
a plants ability to reduce radiological
releases in the event of a nuclear plant
accident, but they are costly. Estimates
range from $15 million per plant on the
low end to as much as $30-$40 million
on the high end. Facing such an invest-
ment, some plant owners may decide re-
tirement is the prudent business choice.
SEISMIC HAZARDSSeismic hazard models are periodically
updated to reect new data and improved
analytical methods; the models are then
used to assess the risks posed to individu-
al plants by seismic activity and to evalu-
ate potential operational and physical
modications necessary to maintain safe
shutdown capabilities. In the aftermath
of Fukushima, the U.S. Nuclear Regula-
tory Commission ordered nuclear plant
licensees to reevaluate the seismic and
ooding hazards against current NRC
requirements and guidance, and if neces-
sary, update the design basis to protect
against the updated hazards.
U.S. nuclear plants are in the process
of performing screening calculations that
will analyze site-specic ground motion
responses based on recently updated seis-
mic hazards. If these calculations nd
that the risk to the plant is substantially
higher than previously determined, a
more detailed seismic risk assessment
may be required. This assessment may
point to needed modications to ensure
safe plant operation and shutdown dur-
ing a seismic event. As with the Fukushi-
ma-induced requirements, such changes
could result in economic impacts exceed-
ing the owners appetite for asset invest-
ment.
For some nuclear plant owners, then,
to be or not to be may indeed be a valid
question in 2013.
Existential ThreatsBY BRIAN SCHIMMOLLER, CONTRIBUTING EDITOR
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WHAT WORKS
Temperature is one of the most
widely measured parameters
in a power plant. No matter
the type of plant, accurate and reliable
temperature measurement is essential
for operational excellence.
Incorrect measurement because ofelectrical effects, nonlinearity or in-
stability can result in damage to major
equipment. Using advanced diagnos-
tics, modern temperature instrumen-
tation can inform a plants mainte-
nance department that a problem
exists, where it is and what to do about
it long before anyone in operations
even suspects that an issue exists.
This ar ticle covers some of the basics
of temperature measurement in power
plants and discusses technical ad-
vances that impart higher a degree of
safety and reliability. These advances
are based on innovative technologies
that are being implemented in process
instrumentation. Implementation of
these new technologies can result in
improved safety along with lower in-
stallation and maintenance costs.
THERMOCOUPLESVERSUS RTDS
Although some specialty temperature
measurements involve infrared sensors,
the vast majority of measurements in
a power plant are made with resistance
temperature detectors (RTDs) or thermo-
couples (T/Cs). Both are electrical sensors
that produce a mV signal in response to
temperature changes.
RTDs consist of a length of wire
wrapped around a ceramic or glass core
placed inside a probe for protection. An
RTD produces an electrical signal that
changes resistance as the temperature
changes. RTD sensing elements can be
made from platinum, nickel, copper and
other materials and can have two, three
or four wires connecting them to a trans-
mitter. Ni120 (120 Ohm nickel) RTDs
were commonly used in the power indus-try, particularly in coal-red plants.
Ni120 at one point was largely used
by rotating machine suppliers on their
equipment, such as pumps. Instead
of buying separate Pt100 wires, these
suppliers would use the same Ni120
wire to build their own RTDs in-house
and provide these RTDs as part of their
equipment.
RTDs are commonly used in applica-
tions where accuracy and repeatability
are important. RTDs have excellent ac-
curacy of about 0.1C and a stable out-
put for a long period of time, but a lim-
ited temperature range. The maximum
temperature for an RTD is about 800F.
RTDs are also expensive. An RTD in the
same physical conguration as a thermo-
couple will typically be about ve times
more expensive. RTDs are also more sen-
sitive to vibration and shock than a ther-
mocouple. Common instrumentation
wire is used to couple an RTD to the mea-
surement and control equipment, making
them economical to install.
A thermocouple sensor consists of two
dissimilar metals joined together at one
end. When the junction is heated, it pro-
duces a voltage that corresponds to tem-perature. T/Cs can be made of different
combinations of metals and calibrations
for various temperature ranges. The most
common T/C type are J, K and N; for power
industry applications, high-temperature
versions include R and S.
Types J, K and N are the most common-
ly used thermocouples due to their wide
temperature range and ability to perform
well in the harsh environments encoun-
tered in power plants.
Thermocouples are selected accord-
ing to the temperatures and conditions
expected:
For temperatures < 1,000F and
mounting locations subject to vibra-
tion, as well as low-corrosion atmo-
spheres: NiCr-Ni (Type K)
For temperatures < 1,832F and corro-
sive atmospheres: NiCr-Ni (Type N)
For temperatures > 1,832F: Pt Rh-Pt
(Types R and S).
Improving Temperature
Measurement inPower PlantsBY RAVI JETHRA, INDUSTRY BUSINESS MANAGER - POWER/RENEWABLES, ENDRESS+HAUSER
AuthorRavi Jethra is the Program Manager- Power Industry at Endress+Hauser.He has over two decades of experi-ence with application engineeringand projects on instrumentation inpower plants worldwide. He holds abachelors degree in instrumentationengineering from Bombay Univ. andan MBA from Arizona State Univ. Heis a senior member of ISA and ASME.
A modern temperaturetransmitter can be set upwith triple redundancy formaximum reliability on criticalprocesses, such as this steamheader. All photos courtesy ofEndress+Hauser
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A thermocouple can be used for temperatures as high as
3100F. T/Cs will respond faster to temperature changes than
an RTD and are more durable, allowing use in high vibration
and shock applications.
Thermocouples are less stable than RTDs when exposed to
moderate or high temperature conditions. Thermocouple ex-tension wire must be used to connect thermocouple sensors
to measurement instruments. The extension wire is similar to
the composition of the thermocouple itself and is considerably
more expensive than the standard instrumentation wire used
with RTDs.
RTDs and thermocouples are both used in power plant
temperature measurement. Each has its advantages and
disadvantages, with the application determining which
sensing element is best suited.
RTDs tend to be relatively fragile and generally not suit-
able for high temperatures or high vibration, so areas suchas steam generators and pump monitoring tend to use
thermocouples, but exceptions exist.
At the Ostroleka power plant in Poland, Endress+Hauser
used a rugged RTD for the rst time. Problems at Ostroleka
involved vibration and electrical noise. Thermocouples
could handle the vibration, but not the electrical noise.
Endress+Hauser developed an RTD that had up to 60g vibra-
tion resistance and handled temperatures up to 812F. The
construction of the RTD is far more robust than other RTDs on
the market, making it suitable for both high temperatures and
extremely high vibration.
With either RTDs or T/Cs, its important to ensure that the
temperature transmitters have the curves and linearization
data built-in to the memory for the specic RTD or T/C without
the need for custom programming.
TRANSMITTERS SUPERIORTO DIRECT WIRING
Most temperature applications in power plants involve di-
rectly wiring a temperature sensor to the control system. Often
engineers wire direct because they mistakenly believe this is a
cheaper and easier solution. Despite the large installed base of
direct wired sensors, the trend is toward using transmitters in
conjunction with temperature sensors. Transmitters save time
and money in installation, improve measurement reliability,
reduce maintenance and increase uptime.
A transmitter converts the mV signal from an RTD or T/C
to a 4-20mA signal or to a digital eldbus output such as
HART, Foundation Fieldbus or Probus PA in the case of
a smart transmitter. Either of these outputs can be trans-
mitted over a twisted pair wire for a considerable distance.
Smart transmitters incorporate remote calibration, ad-
vanced diagnostics and built-in control capabilities and
some are capable of wireless operation.
Direct wiring requires sensor extension wires from the
___________
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sensor to the automation system input
modules. For thermocouples, these wires
are expensive and sometimes fragile.
RTDs can use inexpensive copper wires,
but some RTDs have up to four wires.In a power plant, the automation sys-
tem can be a few hundred feet to even
thousands of feet from the temperature
sensors. This can amount to a large
amount of money for installation de-
pending on the number of sensors and
the distances involved.
Aditionally, over long wiring dis-
tances, Electromagnetic Interference
(EMI) and Radio Frequency Interfer-
ence (RFI) can affect the signal. Theelectrical output from a T/C is only a
few mV and can be completely over-
shadowed by RFI/EMI, depending on
the installation. This can result in false
alarms and occasional trips.
A typical power plant has many
sources of EMI and RFI. On-site power
generation and transmission equipment
are major sources of electrical noise, but
plants also have numerous large rotating
machines with huge electrical elds. By
using transmitters with that comply with
the IEC61326 standard, temperature
measurement can be made immune to
EMI/RFI problems, even in electrically
noisy environments. Temperature trans-
mitters are available that accept more
than two dozen different types of RTDs
or thermocouples, and RTD inputs with
two, three or four wires. These sensors
can be connected to a transmitter with-
out the need for special programming.
ADVANCED TRANSMITTERFUNCTIONS
Todays smart transmitters offer func-
tions that were unheard of 20 years ago.
The extra cost of a smart transmitter is
more than paid back with functions that
reduce maintenance time and prevent
failures that can shut down a power plant.
For example, most transmitters have
a back-up function so that critical and
safety relevant temperature measurement
points can be constructed in a redundant
manner. Here, two sensors are connected
to the transmitter. If one sensor fails, the
transmitter automatically switches to the
second sensor.
The failure of the rst sensor is trans-mitted and is simultaneously shown on
the transmitter display. By using the back-
up function of the transmitter, the tem-
perature measurement point down time
is reduced by up to 80 percent. When this
feature prevents a process shut down, it
more than pays for the cost of the trans-
mitter and the redundant sensor.
For critical measurements, its also pos-
sible to set up a triple redundant system.
In this case, three temperature sensors ina steam pipe to the middle-steam header
are set up with a two-out-of-three vot-
ing scheme for increased reliability and
safety.
Smart transmitters also detect prob-
lems such as T/C drift and low voltage,
allowing maintenance technicians to
perform planned and proactive mainte-
nance instead of just reacting to failures
after they occur.
Because of its physical construction,
measurement points recorded by ther-
mocouples tend to drift. One of the main
reasons for this is the migration of ma-
terial from one leg of the measurement
element to the other. The time span dur-
ing which a thermocouple will measure
accurately tends to vary from just a few
days to a number of years.
To determine the availability and ac-
curacy of a thermocouple, its very im-
portant to recognize drift when it occurs.
With two connected thermocouples, the
transmitter constantly compares the two
measured values and, should the result
exceed the prescribed difference, will is-
sue an alarm.
Modern temperature transmitters also
have the ability to provide a low voltage
warning if the potential drops below
a threshold value. With older technol-
ogy transmitters, when voltage drops, the
unit continues to send a signal, although
it could be off by as much as 25 percent or
more from the actual value.
In applications where fast response
time is needed, customers use grounded
thermocouples, but this thermocouple
type may cause a ground loop. This is
avoided by using transmitters with supe-rior galvanic isolation, up to 2kV galvanic
isolation on most commercially available
transmitters.
Galvanically-isolated transmitters in
general also provide superior noise rejec-
tion as well as protection from electrical
transients and surges in electrically noisy
environment or during weather extremes
such as lightning or thunderstorms. The
current generation of temperature trans-
mitters has a galvanic isolation that isabout three to ve times better than pre-
vious transmitters.
CURING MAINTENANCEHEADACHES
Smart transmitters diagnose many
common problems that might take sev-
eral days for a maintenance technician
to nd, diagnose and repair. For exam-
ple, it may be very difcult to diagnose
if a temperature loop is suffering from
ground loops, noise, bad connections,
cable breakage or many other problems.
Without a smart transmitter, a technician
just has to plod through the sensor and its
electronics, step by step.
Its not just mechanical components
that undergo wear and tear in a power
plant; the electrical parts also see ag-
ing and corrosion. Process sensors and
instruments in the power industry fre-
quently work in very aggressive envi-
ronments. Cable glands are rarely 100
percent sealed, and eventually corrosion
on the terminals or even the connection
wire becomes a reality. Corrosion on the
sensor connection system (sensor ele-
ment, eld wiring and transmitter termi-
nals) can lead to errors in measurement.
Although the atmosphere in a power
plant may not have as many corrosive
materials as a chemical plant, dust and
other materials can cause corrosion
over a period of time. Because the ter-
minals in a transmitter and the lead
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www.power-eng.comFor info. http://powereng.hotims.comRS# 9
wires are made of different materials,
corrosion can occur.
In power plants, a manual check of
all the sensor connections is virtually
impossible. Temperature transmitters,on the other hand, continuously moni-
tor resistances of the sensor connection
cables,and give a warning so that preven-
tive maintenance measures can be carried
out with no measurement degradation.
Electronic devices can fail when ex-
posed to extreme temperatures. Smart
transmitters have a built-in RTD at the
electronics module that monitors ambi-
ent temperature. When temperature ex-
ceeds the limits the unit is specied for, itgives a warning indication.
The mechanical, thermal and elec-
trical pressures in power plants are, in
many cases, enormous. This stress on
sensors can quite often lead to dam-
age such as cable/sensor breakages or
sensor short circuits, the natural result
of which is fai lure of the measurement
point. Overstepping the allowable sen-
sor circuit resistance is also seen as a
break in the line. This can occur in
both RTDs as well as thermocouples.
Cable breakage or sensor short
circuits are detected by the transmit-
ters analysis electronics and transmit-
ted to the automation system. Devices
that operate with a 4-20mA current
output do this in the form of a faultcurrent (NAMUR 43) or HART data
output, while smart transmitters send
indications over their digital network.
In addition to transmission of the
measured signal, the HART protocol also
enables the transmission of digital infor-
mation superimposed on the 4-20mA
signal. This information can contain de-
vice status, maintenance requirements,
sensor failure indication, sensor open cir-
cuit indication and much more.The problem with a number of process
control systems in the power industry is
that they do not have a built-in request
system for the digital HART informa-
tion. In that case, HART signals can be
categorized using DIP switches, and then
transmitted as simple on-off discrete sig-
nals to the automation system. The four
categories are Failure detected, Ser-
vice mode, Maintenance required and
Out of specication. In short, smart
transmitters can detect, identify and re-
port small problems before they become
large problems.
When the technician arr ives at the
transmitter to effect repairs, he or she
sees a large and brilliant blue back-lit
display that provides a clear reading
from a distance of 8 to 10 feet. The dig-
its on a new transmitter display are at
least twice the size of any of the older
devices. When the technician needs
an instruction manual, schematic or
other support material, these days he
or she can just call it up on a cell phone
app or a tablet browser.
THERMOWELLSPROVIDE PROTECTION
RTDs and T/Cs can be surface mount-
ed, installed in a probe or inserted into
a thermowell. In severe power plant
environments, a thermowell acts as a
barrier between the process and sens-
ing element. It provides protection from
Endress+Hauser TMT 162temperature transmitterwith big display, mountedon a thermowell.
____________
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QUIETLY SOLVING YOURACOUSTIC AND EMISSIONS
CHALLENGES
Exhaust Inlet Retrofit Turnkey
Do you have a turbine system that needs updating or replacement? Universal is your singlesource for inlet and exhaust replacement. From site survey to commissioning, we have theexperience and expertise to simplify your complex project.
One single point of contact provides you:
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For info. http://powereng.hotims.comRS# 10
Von Karman Trail Effect (vortex
shedding around the thermowell).
Proper diagnosis can identify all but
the most unusual thermowell failures.For example, at the Ostroleka power
plant in Poland, a thermowell on the
outlet of the boiler feedwater pump
was constantly breaking because of the
effects of the Von Karman Trail. The
thermowell broke ve times because
of high frequency vibrations. The
corrosive processes and abrasives, and it
also provides protection when placed in
applications where there is high pressure
and/or owing media.
A thermowell will allow the sensingelement to be removed without inter-
rupting the measurement as the sensing
element is inserted into the thermowell
from outside the pipe or vessel.
A thermowell adds considerable cost to
the measurement point because the ther-
mowell has to be inserted into the pipe,
furnace or vessel. This often entails cut-
ting into the pipe and welding a xture.
Because the thermowell adds a layer of
protective metal, it slows down the re-sponse time of the sensor. Thermowells
are subject to failure, especially in the
severe environments found in power
plants. Excess pressure, vibration, tem-
perature and corrosion are major causes
of thermowell failure.
The four main failures of
thermowells are:
Mechanical - Bending or breakage
caused by an applied force which
is beyond the limits of the ther-
mowells yield strength. High-pressure steam is a likely culprit.
Corrosion - Induced by chemicals
and/or elevated temperatures.
Erosion - Resulting from high-
speed particle impingement on
the thermowell.
Vibration/Fatigue - Failure due to
Thermowells at a power plant in Poland werebreaking because of the Von Karman Traileffect. The solution was a stronger thermowelland a vibration-resistant RTD sensor insert.
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Scan for Career Opppotunities
www.stanleyconsultants.com
800.553.9694
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solution was to replace the thermow-
ell with a stronger Endress+Hauser
Omnigrad M TR10 thermowell, tted
with an ITHERM StrongSens vibration
resistant RTD sensor.
HANDLING HIGHTEMPERATURES
Power plants can generate extremely
high temperatures that often cause
measurement problems. For example,
in energy-from-waste plants, furnace
temperature is a critical measurement.
Burning the waste at high temperatures
minimizes the release of harmful emis-
sions. To accurately record the tempera-ture in the furnace, three or more tem-
perature thermowells are inserted into
the furnace directly above the ame.
Because of the very harsh conditions
in the furnace, conventional probes
made from Incoly 800HT alloy will
typically fail after three or four months
of service. Because the probes are sited
in an elevated position, changing them
can be difcult. In addition, each time
the furnace is opened there is the pos-
sibility that cooler air will enter or thathot gases will escape, both of which can
decrease the efciency of the process
and cause health and safety concerns.
A recent trial showed that
Endress+Hauser temperature probes
with thermowells made from SD75
alloy can withstand the extreme
temperatures up to 3,000F typically
found in the furnace of an energy-
from-waste facility. During the
12-month trial, two probes made fromthe new alloy were used alongside
standard thermowells. In a like-for-
like comparison, the new probes lasted
three times longer than their Incoly
800HT counterparts.
The high chromium and silicon content
of the alloy increases the stability of the
instrument and makes it highly resistant
to corrosion at high temperatures. The
presence of these elements promotes the
formation of a protective oxide scale,
making the alloy resistant to attacks fromsulfur, vanadium, chlorides and other
salt deposits.
SUMMARYAdvanced instrumentation is greatly
improving temperature measurement
in the power industry. The benets
of using smart transmitters instead of
direct wiring includes installation cost
savings, reduced downtime and proactive
maintenance through the use of advanceddiagnostics. When a power plant has to
be shut down because of a failed sensor,
the cost could run into the millions of
dollars. Smart transmitters can tell a
plant that a problem exists, where it is
and how to x it anticipating failures
before they occur.
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www.power-eng.com
torque-to-size ratio and the double-
opposed lip seal design is forgiving to
dirty or contaminated air.
Also, the low-fric tion performance
of K-TORK provides a speed-con-
trolled, smooth valve operation, elimi-
nating the risk of water hammer cre-
ated by the high pressure drop.
Finally, longer run time between
shutdowns demands increased reli-
ability from the equipment in these
critical applications. In particular,
as the number of plant maintenance
personnel has decreased, actuators
that reduce maintenance (seal replace-
ment) time and work orders have a di-
rect payback to the owner, especially
when valve life can be signicantly
increased through improved actuator
performance.
The Rotork K-TORK vane type
valve actuator has solved a
difcult ow control applica-
tion found in many coal-red power
plants high-pressure bottom ashspray valve control.
High-pressure spray water is used to
sluice bottom ash and pyrites from the
boilers hopper bottoms and to carry
the ash out of the plant. The valves
used are typically ANSI Class 300 dou-
ble-offset high-performance buttery
designs ranging in size from 3 to 12,
automated with double-acting actua-
tors. They cycle from four to 10 times
per day and discharge to atmosphere,
creating a very high pressure drop. The
ow media is recirculated ash water
that is abrasive and ows at pressures
between 400 and 500psi.
In plants owned by AEP, Duke En-
ergy, Luminant Generating and other
utility companies around the world,
K-TORK actuators have provided over
10 years of maintenance-free service
while preserving the life of the valves
and valve seats in these arduous duties.
Forty actuators were installed in 2001
(20 per boiler unit) and have provided
12 years of operation with no down-
time or maintenance required. All still
have the original, durable lip seals
Among the challenges, it is impera-
tive that the valves close fully and
with zero leakage in a high pressure
drop state. If the valve disc moves
even slightly from the seat, the abra-
sive, high-pressure water will wire-
draw or cut the buttery valve seat.
Traditionally, rack-and-pinion or
scotch-yoke actuators have been used
in this application, but slop or hys-
teresis in the rotary-to-linear conver-
sion allows for the pressure in the
pipe to move the disc from the seat,often causing premature failure of the
valve after a period of only three to 12
months.
The problem becomes more acute
when multiple valves are leaking, low-
ering the available back-pressure at
the header, which makes it difcult or
impossible to move the ash from the
boiler.
When assembled to the valve with
a No-Play coupling, the K-TORK ac-
tuator has zero lost motion, slop or
hysteresis. The one-piece vane and
drive shaft cannot be back-driven and
will hold the disc of the valve rmly
in place.
Additional challenges include the
location of the valves on a manifold at
the bottom of the boiler where space
is critical and plant air can be poor
quality. K-TORK provides the smallest
Achieving
Success in BottomAsh Spray ValveControl
Rotork K-TORK actuators installed on twounits at the AEP Pirkey Power Station in eastTexas. All photos courtesy of Rotork
The K-TORK double-opposed lip seal isforgiving to dirty or contaminated air.
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www.power-eng.com
THE (LOof Win
Tur
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www.power-eng.com 23
on name recognition or other reasons
that are equally unrelated to long-term
project viability.
The contributing factors to a failed
turbine selection are plentiful, al-
though several have become prevalent.
The following is a sample of ve com-
mon mistakes that occur during wind
turbine technology selection as well
as strategies that can be employed to
make your choice of technology a suc-
cessful one.
OVERVALUINGCAPACITY FACTOR
Of any metric that is considered as
part of a technology selection effort,
perhaps none gets more attention than
capacity factor. While this efciency
indicator has its place in any wind tur-
bine evaluation, it should not be the
only factor in ones decision.
The key issue with over-reliance
upon capacity factor is deception.
Consider that in a given layout, it is
not uncommon to observe a capacity
factor differential of up to 10 percent
between competing turbine mod-
els. However, many project owners
BY AARON ANDERSON, BURNS AND MCDONNELL
W
ind energy
development
is complex. It
requires care-
ful evaluation
of numerous factors, including a sites
wind resource, permitting require-
ments, nancing structure, balance-of-
plant design and more. Before ground
is ever broken, a typical owner invests
many years and countless dollars into
consideration of these basic elements
of wind farm development. However,
perhaps no factor inuences the long-
term viability of a project more than
selecting the optimal wind turbine
technology. And unfortunately, most
wind farm owners are applying less
and less rigor to this critical step.
The primary difculty with select-
ing the right technology is not all wind
turbines are created equal. They vary in
size, performance, cost, reliability and
even appearance. However, as more
players continue to enter the growing
wind industry, a greater number of
inexperienced developers are enter-
ing into multi-million dollar agree-
ments for wind turbines based solely
The capacity of a turbine may be more important thanthe overall efciency turbine when planning a wind powerproject is important to avoid an underperforming plant.
T) ART
ineTechnology Selection
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www.power-eng.com
For info. http://powereng.hotims.comRS# 13
terrain and wind resource. Many owners
limit this evaluation to selecting a ma-
chine based solely on its IEC classica-
tion (e.g., IA, IIB, etc.). However, while theIEC guidelines may be useful as a prelim-
inary screening technique, the suitability
of a turbine for a particular site extends
well beyond these codes.
There are a variety of considerations
that go into determining site suitability.
While these generally vary by site, the fol-
lowing is a sample of three critical ques-
tions that should always be asked when
evaluating the operating and design char-
acteristics of a turbine: What is the project terrain like?
A project site with complex terrain
may result in areas of signicant up-
ow and elevated turbulence levels,
potentially impacting the longevity
and long-term energy production of
the machine. Similarly, if conditions
Capacity factor can be a misleading
statistic. This metric clearly deserves
consideration, but, as
part of any success-ful turbine selection
strategy, capacity fac-
tor should be limited
to a nancial modeling
input. Consideration
of this metric in any
greater light may result in a highly ef-
cient yet underperforming project.
SITE SUITABILITY
While capacity factor may be the mostmistakenly relied upon metric during
turbine selection, perhaps none is more
commonly misused than site suitability.
When selecting an optimal turbine for a
particular project site, one must always
consider the operating and design charac-
teristics of the machine against that sites
erroneously equate this differential
with viability, assuming that the less
efcient machine is
also less attractivefor their site. On the
contrary, if that less
efcient machine is
also double the ca-
pacity (e.g., 3 MW
versus 1.5 MW), it
may produce nearly twice the annual
energy despite the 10-point disparity
in capacity factor. Recognizing that
balance-of-plant construction costs
are generally not linear (i.e., it doesntcost twice as much to build the project
with the 3.0 MW turbine), the needle
often tends to move towards the bigger
machine, particularly at larger wind
farms, projects with attractive power
purchase agreement rates and projects
that are not capacity constrained.
The key issue withover-reliance oncapacity factor isdeception.- Aaron Anderson
_____________
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Solutions for Success
www.WINDPOWERexpo.org
Scan this code with your
smartphone to learn more!
WINDPOWER is theSource to Find Your Business Solutions
The American Wind Energy Association (AWEA) is a national trade association
representing wind power project developers, equipment suppliers, services providers,
parts manufacturers, utilities, researchers, and others involved in the wind energy industry.
AWEA also represents thousands of wind energy advocates from around the world.
AWEA WINDPOWERConference & Exhibition is the annual focal point for those who
work in the wind energy industry; its where serious wind professionals convene to growtheir companies, find real solutions to business challenges, learn from industry leaders and
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www.power-eng.com
$35,000 to $50,000 per turbine per
year seems almost negligible when
compared to the turbine price, its im-
pact can be substantial.
Nearly every turbine supplier will
require the use of their O&M services
throughout the turbine warranty peri-
od. Not only should this requirement
be treated as an intrinsic cost of tur-
bine selection, but it is also important
to consider all aspects of the proposal.
To more fully understand these, ask
questions like:
Does the proposal include both
planned and unplanned mainte-
nance?
Who pays for the crane if required
for repairs?
Are spare parts required to be pur-
chased upfront or at the end of the
contract?
Is my availability guarantee cov-
ered by the service agreement,
and if so, does that lower the po-
tential limit of liability?
Is in and out coverage included
in the service fee?
Answers to these questions may
inuence the selection of an optimal
turbine as well as potentially impact
the long-term viability and production
from equipment supply (e.g., is the
turbine furnished with an internal
transformer or will it require an owner-
supplied pad-mount?) to service
offerings (e.g., is the supplier installing
tower cabling or is the owners
contractor required to do it?). Similarly,
different turbine manufacturers may
offer varying warranty periods; climb
assists versus service lifts; differing
quantities of spare parts and special
tools; varying durations of on-site
support during eld activities; and
other similar disparities.
Regardless of the differences or their
subtleties, bid prices must always be
adjusted at the onset of any successful
turbine evaluation the goal should
be an apples to apples comparison
wherein all bids are equivalently and
uniformly evaluated. Failure to do so
may lead to selection of a suboptimal
machine for your site, adversely
impacting the long-term nancial and
operational performance of the project.
EVALUATING SERVICEVERSUS SUPPLY
Another area where a turbine evalu-
ation often goes awry is in the assess-
ment of the service proposals. While
the cost of these proposals generally
are sufciently severe, it may be nec-
essary to utilize a higher-classica-
tion machine than would otherwise
be called for by the IEC guidelines. What is the wind shear across
the swept area of the turbine?
Evaluation of wind shear is com-
mon, although most assessments
end at hub height. However, it is im-
portant to recognize that shear can
decrease (or ev