magazin pe mar 2013

8/10/2019 Magazin PE Mar 2013

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March 2013 www.power-eng.com

EMISSIONS CONTROLUNDERSTANDING YOUR OPTIONS

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PRB COALCHALLENGES AND SOLUTIONS

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March 2013 www.power-eng.com

EMISSIONS CONTROLUNDERSTANDING YOUR OPTIONS

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PRB COALCHALLENGES AND SOLUTIONS

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Power Engineering

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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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6/66

www.power-eng.com

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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www.power-eng.com

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


11/66

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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www.power-eng.com

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


13/66

ENERGY UNDERSTOOD

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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


15/66

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

project that taps the areas abundant natural gas resources. With Catgas

generators, you can deliver the power closer to the population centers, without

requiring large power grids that can be difficult to secure. And theyre backed by

the support of local Cat Gas Power Systems experts, who will help you maintain

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16/66

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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


17/66

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18/66

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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


19/66

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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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20/66

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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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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:

Site Survey Design Improvements Demolition

Installation Budget Preparation System Inspection

Commissioning Project Management

(888) 300-4272 | [email protected] | www.UniversalAET.comUniversal AET designed and manufactured this exhaust system for aWestinghouse 501D5 gas turbine. This system was installed at the Puget SoundEnergy - Fredonia Station in Mount Vernon, Washington.


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

COLLABORATE

We dont have preconceived solutions to

your complex Power Generation needs.We listen to your concerns and evaluate

your options to engineer a solution that

will work for you now and in the future.


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.


25/66

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www.power-eng.com

THE (LOof Win

Tur


27/66

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


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

experts, discover the latest in industry products and services, and reconnect with colleagues

and friends.

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30/66

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

magazin pe mar 2013

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