microturbine generators
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Micro turbine
Generators
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Micro turbineGenerators
ditedby
M J Moore
rofessional
ngineering
ublishing
Published by Professional Engineering Publishing
Bury StEdmundsandLondon UK.
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FirstPublished 2002
This publication
is
copyright under
th e
Berne Convention
and the
International Copyright Convention.
A ll
rights reserved. Apart
from any fair
dealing
for the
purpose
of
private stud y, research, cri ticism
or
review, as permitted under the Copyright, Designs and Patents Act, 1988, no part may be reproduced,
stored in a retrieval system or transmitted in any form or by any means, electronic electrical ,
chemical , mechanical , photocopying, recording or otherwise, without th e
prior
permission of the
copyright owners. nlicensed multiple copying of the
contents
of this
publication
is
illegal
Inquiries
should
be
addressed
to: The
Publishing Editor, Professional Engineering Publishing Limited,
Northga te
A venue , Bury St Edmunds, Suffolk, IP32 6BW , UK . Fax: +44 0) 1284 70527 1.
2002
TheInstitutiono fMechanical
Engineers,
unless
otherw ise stated.
ISBN 186058391 1
A CIPcatalogu e recordfo rthis bookisavailable
from
theBritish Library.
Printed by The Crom well Press, Trowbridge, W iltshire, UK
ThePublishersare not responsible for anystatem ent m ade inthis pu blication. Data, discussion, andconclusions
developed by authors are for information onlyand are not intended for use without independent substantiating
investigation on the
part
of
po tential users. Opinions exp ressed
a re
those
of the
Authors
and are not
necessarily
those
of the Institution of M echan ical Engineers or its Publishers.
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ont nts
About theEditor ix
Foreword
xi
Chapter
1 An Introduction to Micro turbine Generators
ABullin 1
Chapter
2
Micro turbine Generators
Next Generation
S L
Ham ilton
21
Chapter 3 Analysis of Micro and Mini turbine Competitive and Supply
Marketsin
Europe
T
Shane
27
hapter4 Future PotentialDevelopmentsofMicro turbine Generators
ybridCycles
and
Tri generation
E
M acchi
andS Campanari 43
Chapter
5
Design Reliability
of
Micro turbines
I J
Stares
an d
Q JMabbutt
67
Chapter
6
Field Experience with Micro turbines
in
Canada
RBrandon
73
Chapter
7
Design Problems
in
Micro turbine Generators
K RPullen R M artinez-Botas and K
Buffard 85
Chapter 8
Tip leakage
Flow: A Comparison between Axial and
Radial Turbines
RDambach H P Hodson
and
IHuntsman
97
Index 1 9
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bout
the
Editor
Michael Moore
a
former
Editor
of the
IMechE Journal
of
Power
and
Energy
was
em ployed
for m any years
in the
Research Division
of the
Central Electricity Generation Board.
As
Head
of Engineering Science Division and Programm e Manager for Turbine Plant Research he
gained wide experience
o f
power station plant.
In
1989
he
became Com m ercial Developm ent
Manager
in National Power before retiring to become an independent consultant. Michael
Moore is the author of 25 papers and editor of two books on turbine and condenser plan
design.
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orewor
Since
the
introduction
of
electricity supply systems
and
distribution
by a
grid network
the
economies
of
scale have been recognized. Generating plant have become
progressively
larger
culminating
in
unit outputs
of
1300
MW from
nuclear
and
even some
fossil-fuelled
plant.
The
relativelyrecent availabilityofnaturalgas at economic priceshas led to thedevelopment of
extremely large gas turbinesincombined cycle generating at thermal
efficiencies
of up to 60
per cent. It is therefore surprising that a niche market has appeared for micro-turbine
generators MTGs) with output powerof20-500kW.
Theirappearance
on the
generation scene
has
been made possible
by the
development
of
their
component parts. Tiny radial compressor
and
turbines
are
notoriously
inefficient and
prone
to
excessive
tip
leakage. Modern precision manufacturing techniques
and
design methods using
computational fluid
mechanics CFD)
has
substantially improved their performance. High-
speed permanent magnet alternators
and
bearing systems have made
possible
the
direct drive
arrangements, which remove the cost and complexity of gearboxes. Lastly, bu t most
importantly, modern, solid-state, power electronics
has
enabled
the
potentially unsteady
kHz
outputto be convertedto ahighly stable voltagea tgridfrequency.
Disadvantages remain. Even with exhaust
gas
heat recuperators, these small units achieve
onlysome30 percent thermale fficiency. Turbine entry temperatures, the key to gas turbine
efficiency
have limited development potential due to the difficulties of cooling such tiny
components. With this relatively high fuel consumption
how can
these devicespenetrate
the
market?
While
the
introduction
of
MTGs
is in its
early stages, their relative simplicity makes them
suitable
for
mass production with correspondingly
low first
costs. Whereelectricity
is in
short
supply,
and
grid strengthening
is
expensive
and
delayed,
the
advantage
of
such units
as
distributed
generation
has
been recognized. MTGs obviously have
a
role
on
remote
oil rigs
where
fuel
is availableand nogrid connection is feasible. Combined heat andpower CHP)
projectsarealso potential applications and, again more recently, back-up power forcomputer,
internet,and IT installations
benefit
from the high quality supplyfrom the
power
conditioning
units.
Their competitors arereciprocating gas engines andgenerators and the fuel cell. The former
it
is
claimed, require more maintenance,
and the
latter
is
more complex
and may be
less
reliable.
Looking ahead, the combination of MTGs an d
fuel
cells could raise overall
generating
efficiency
to 60 percento rhigher.
The emergence
of MTG
technology prompted
the
IMechE
to
hold
a
Seminar
in
London,
December2000
to
introduce
the
concept. Since then
the
papers
from the
seminar have been
up-dated and are reproduced in this volume. They cover the field from the general
arrangement
of
components,
the
main design problems,
the
market envisaged operating
experience to date, the fluidmechanics ofsmall turbines, and the thermodynamic cycles for
their
futureapplication. Ihopeyou find thevolumea useful introductionto thesubject.
M
oore
itor
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An Introduction to Micro turbine
Generators
Bullin
bstr ct
This Chapteridentifies the main elements of a micro-turbine generator and the key enabling
technology. The elements include the micro-turbine engine, turbo alternator, recuperator,
power conditioner,
and gas
boost compressor. Features, advantages,
an d
benefits
of
each
element as preferred by Bowman Power Systems Limited are described and alternative
solutions are discussed. T he
features
an dbenefits of a micro-turbine cogeneration system are
presented and described.
1 1
Introduction
The
following
is a brief introduction to micro-turbine technology.
Micro-turbine generators MTGs) are based on five key areas of technology: micro-turbine
engines running
on
liquid
or gas
fuel;
turbo alternators
to
produce electrical power;
recuperators heat exchangers) to achieve high engine
efficiency;
power conditioners to
convert
the
power
to
meet customer needs;
and gas
boost com pressors
to
provide natural
gas
fuel at an
appropriate pressure.
There are various approaches to these areas of technology, but
this
Chapter concentrates on
the Bowman solution to the design challenges, although alternative solutions are mentioned
and discussed.
Development of m icro-turbine and associated enabling technology has been m arket led; the
driving force being the customer need fo r competitively priced distributed power solutions
and theeaseof installation and use of the equipment.
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An Introduction toMicro turbineGenerators
Fig 1 1Turbog en cross section
1 1 3 Recuperators
Durable heat exchangers of high
effectivity
and low cost are needed to increase the
efficiency
of ga s
turbines
to the
levels needed
to
compete with reciprocating engine-based power
generation
systems. The function of
these heat exchangers
is to
extract heat from
the gas
turbine exhaust
gases in
order
to
preheat
the air
used
in the
com bustion
process
and
thereby
reduce the
amount
of fuel
used
to
reach operating temperature.
The Bowm an recuperator is a primary surface type manufacturedfrom
stainless steel
forlong
life. With an
effectivity
of about 90 per cent the fuel consumption of the micro-turbine
engine is approximately halved doubling the MTG efficiency from 15 per cent to about 30
per cent.
1 1 4 Power
onditioners
The electrical output frequency of a turbo alternator is typically 1000-3000 Hz and must in
mostcases
be converted to a 50 or 60 Hz useable ou tput. A microprocessor controlled power
conditioner carries
out the frequency
conversion
in
addition
to
other power conditioning
and
utility
connection
functions to
provide electrical power
of
appropriate quality
and
features.
The power conditioner controls the output frequency independently of turbine
speed
and
facilitates the
variation
of
speed with load
to
reduce
fuel
consumption.
The
power conditioner provides
the functionality to
allow
the MTG to
operate
in
parallel w ith
the
u tility supply
in
various modes
or as a
stand-alone system. Integrated engine control
an d
3
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4 Micro turbine Generators
management capability, together with remote control
an d
monitoring,
is
either
a
further
feature of this module or is provided by means of separate modules.
1.1.5
Gas
boost compressors
Natural
gas is the fuel of
choice
for
stationary power plant. Pipeline
gas is
usu ally supplied
to
small users at low
pressure
typically less than 1 psi. An MTG requires gas at 60-80 psi;
therefore
an efficient, low-cost, durable, gas boost compressor is needed.
Su itable technology
is
being developed
in
association with experienced
air and refrigeration
compressor manufacturing companies and commercially acceptable units are available from
tw o
suppliers
subject to
completion
of certification. It is
thought that more suppliers will
offer
product as the M TG
indu stry need grows.
1.2 Bowm an Technology
1.2.1 Micro turbine engines
These first generation, very small, high-speed, gas turbine engines are simple radial designs,
and as stated earlier, they are closer in concept to low-cost turbochargers than the more
complex
and
costly axial designs
of
large industrial engines which
are
often derived
from
aero engines.
A
bearing system
is
required
to
support
the
high-speed rotating shaft;
the
bearing system also
has to
oppose
the
axial
forces
generated
by the
aerodynamic load.
Any
contacting/rolling element bearing will
be life
limited
due to the
contact
forces
the
bearing
is
exposed
to; for a
system with
an
installed
life of circa five
years between
major
engine overhauls, contacting bearings should be avoided if possible.
There has been experimentation with gas turbines in the power ranges of
25-400
kW for
around
50 years. The earlier developers of engines in these power ranges include Rover,
Austin, Ford, GM, and Chrysler, all being automotive biased. These engines all used
reduction gearboxes
an d
could
n ot
meet
the
ef ficiencies
and
man uf acturing costs achieved
by
reciprocating engines at the time, where a large component of the cost was the reduction
gearbox.
Although this type
of
technology
has
excelled
in
auxiliary power unit (APU) applications
in
the aerospace industry, the production volumes have never been high. Typically, total
production numbers fo r
aircraft
AP U s will be less than 10 000 u nits over 10 years, i.e.
circa
1000 units
pe r
year. These engines
are
typically
life
limited
to
circa
10 000
hours, which
is
no t suitable for cogeneration an d prime power application requirements an d they are
expensive due to the aerospace quality production systems andaccessoriesused, and their low
productionvolumes.
Micro-turbine
production is benefiting from the technologies developed for automotive
turbocharger
applications, where the worldwide production of these devices exceeds
50
000 000 u nits a year (KKK, Garret, IHI, Su ltzeret al. .
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An
Introduction
to
Micro turbine Generators
5
The
enab ling technologies
fo r
m icro-turbine systems
h as
matured over recent years, becoming
more
accessible an d cost competitive. These include the electronics fo r power conditioning,
high-speed alternator, ana lysis and design of high-efficiency radial turbomachinery, and low-
cost production techniques of radial turbo machinery components.
The primary objectives of the initial MTG design are that the engine should be low
cost,
durable, and of reasonable efficiency. There is little difference in the materials selected and
the manufacturing
processes
for the manufactured engine components used by the major
micro-turbine engine suppliers.O ne of the main
differences
in the alternative design concepts
is in the type of bearing system used in the machines.
It
is
widely accepted that
the
Capstone Turbine Company
ai r
bearing technology
has
significant technical advantages, such as lower bearing losses than with oil lubrication and the
elimination
of the oil
system components.
It is fair to say
that
in
some quarters this
is
considered to be current state of the art.However, there are
successful
alternative designs that
make use of a variety of oil-lubricated bearings to support the rotating elem ent.
Bowman
experience
is
that
the use of an
inboard, oil-lubricated,
tilting pad
bearing provides
long and trouble free
life,
while th e alternatively used oil-lubricated plain journal bearing at
this location
suffers
high losses, and rolling element bearings w ill provide
insufficient life.
The second generation engines will possibly use active magnetic bearings, which offer
advantages
over ai r bearings in
that
th e axial clearance of the compressor can be actively
controlled
du ring operation to maximize the engine efficiency, and the bearing control system
can
be
used
fo r
real-time condition mon itoring.
A major
benefit
of micro-turbines is the low emissions NO
X
,CO) compared with
conventional reciprocating engines. The combustor design is critical to achieve low
emissions.
The
best emission values achieved
by any
micro-turbine manufacturer
to
date
are
less than 10 ppm NO
X
,on gaseous
fuels.
No company is currently claiming better than 25
ppm NO
X
on
liquid
fuels.
Catalytic combustion is an alternative to conventional combustion and the progress of this
technology will be closely monitored over th e next few years to determine its suitability fo r
use
in MT G s. It is known that experimental machines using catalytic combustion have bee n
developed to prototype stage in USA and Japan although there has been no commercial
release of such machines.
1 2 2 Turbo alternator
1 2 2 1 Introduction
The high-speed turbo alternator
is a key
element
in MTG
technology. Over
a
period
of
seven
years, Bowman has worked with a number of different electrical machine companies, and
individual consultants worldwide, and has built on that experience, aiming always to
internalize its design capability and establish an independent expertise. These machines are
highly stressed electromagnetically, m echanically, and therm ally, and complex in th eir detail;
there
is
much that needs
to be
understood before they
can be
designed with confidence
fo r
long
working life.
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6 Micro turbineGenerators
On the
manufacturing
side
particularly
in the
areas
of
core assembly
and
winding, magnet
provisionand
bonding,
and
sleeve construction
and
pre-stressing, there
are a
small number
of
capable suppliers with
the
necessary capability
and
expertise
to
provide components
and
sub-
assemblies
to the
quality required. Several
of
these have come
from
the
aerospace industry.
Bowman possesses
a
deep understanding
of
machine topologies alternative
to the
synchronous permanent-magnet PM) drum type. It has for a long time had an association
with Southampton University, cemented by a key dual appointment, andbenefits in many
ways: e.g. finiteelement studiesofmachine configurations, modelling of complete electrical
system performance, development
of
proprietorial design software,
a
research programme
in
certain
types
of
rotor power loss, micro-structure examination
of
material sections, etc.
Intermsofspecific
output
powerortorqueperunit volumeor perunit mass) and
efficiency,
thehigh-speed generator
is far in
advance
of the
conventional synchronous machine
of
similar
power output. Designs arecurrently being manufacturedandsupplied inquantity, atpowers
from 40 to 165 kW,with speeds rangingfrom 105 000r/minto 55 000r/min. Confidence in
the
technology
issu fficiently
high that machines have been designed
at 300 kW, 500 kW , and
atmore than
1 MW.
The values
of
power density
and efficiency
achieved
in
high-speed alternators
are now
both
sufficiently
high that there
is
really little pressure
- and
also,
it
must
be
said, little scope
- for
further improvement. The electro-magnetically active parts of an alternator providing
165 kW, for
example, corresponding very roughly
to the
average power demand
of
some
35 domestic houses, pack into
an
overall length
of
about
270 mm and a
diameter
of
about
120 mm, and
produce little more waste heat
as
loss power) than
a
two-bar electric
fire.
Furthermore,becausethemachineis sosmall, therearetypicallynouncontrollable problems
due to
resonant vibrations
of the
complete shaft system within
the
rated speed range;
centrifugal force is not so
high
as to
prevent
the
rotor being held
safely
together
by a
containing sleeve;
and
bearings
are not
made excessively large and expensive)
by an
unduly
heavysupported rotor mass.
Figure 1.2 illustrates a 50 kW high-speed alternator rotor mounted with the gas turbine
compressor andturbine wheelsand in the foregroundan 110 kWhigh-speed alternator rotor.
Length
of
this rotor
is
about
250
mm.)
Fig 1 2 urbo alternator
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An
Introduction to
Micro turbine Generators
1.2.2.2 echnology comparison
1.2.2.2.1 PM drum type heteropolar
The heteropolar drum-type machine, incorporating rare-earth permanent magnets, with
electro-magnetic stator-rotor interaction
acrossa
radial gap,
is the
industry preferred topology
having
been adopted by most leading manufacturers.
It
is known that as power rating increases the optimum design speed for the
turbine/compressor necessarily reduces- principal constraints being the internal mechanical
stress
due to centrifugal force and
system dynamic considerations. Very similar
effects
apply
in the drum-type PM m achine, and all design experience has shown that there is a good m atch
between
the
optimum speed
of
turbomachinery
and
alternator, which therefore mount
naturally together on a common shaft. This is true, in particular for the single-shaft
arrangement, in which the po wer turbine, and therefore alternator, rotate at the full speed of
that
shaft. It follows that the alternator is also easily designed for the alternative, dual-shaft, o r
free
power turbine arrangement,
in
which
the
power turbine runs
at an
independent speed,
lower
than
that of the m ain turbine shaft.
1.2.2.2.2
PM disc type
This alternative topology has it s champions and comprises a multiplicity of interleaved
stator-rotor discs with axial gaps. The Bowman view is that the disc approach is limited in
speed and sub-optimal in other performance parameters. The disc-type alternator finds
practical app lication in com bination w ith a free power turbine, as described above, rather than
in higher speed,
and
cheaper, single-shaft arrangements. Interleaving discs
are
awkward
for
assembly/disassembly,
and the
structure
is not
cheap
to
manufacture. Magnet surfaces
are
necessarily exposed or thinly covered, with risk of corrosion, disintegration, and
dispersal
of
this brittle material within the machine over time, whereas in the drum structure the magnets
are
completely
and
tigh tly enclosed.
1.2.2.2.3
Bowman
designfeatures
Winding
configuration
The preferred winding arrangement is not simple three-phase, but double three-phase with
two sets of three-phase w indings lying in adjacent slots. The effect of this is greatly to
reduce
important components
of
internal stray power
loss.
Side effects that must
be
accepted
are a
doubling of the number of connection leads and a need for two (each half-rated) external
rectifier b ridges instead of one.
Rotor
s tructureandre taining sleeve
A pre-stressed retaining sleeve, to hold the magnets on to the steel hub against centrifugal
force,
is essential. Preferred material is carbon fibre which
offers,
at present the highest
lightness-strength combination of any established technology and is electrically inert.
Bowman conclusion, based on some six years experience, is that with proper control of sleeve
manufacture
and
assembly
and attention to simple but critical mechanical features, carbon-
fibre technology is the best currently available.
Alternative
designs using inconel and titanium sleeves are available, and are used by other
manufacturers.
7
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Micro turbine Generators
Thermal design
and ooling
The standard cooling arrangement
is an
external cooling jacket
to the
stator core, with water
or oil
coolant,
and an
internally
forced flow of
cooling air, typically
at a few
litres
pe r
second
flow
rate. Inlet coolant temperatures
are 70 C as
standard, allowing ample headroom
for
remote heat exchange between thehottest design ambient of 45 C and the inlets. Alternative
designs
for
external air-cooling
are
available, though
possibly
with some penalty
on
specific
output.
Internal hot-spot temperatures arekept below about 160 C compatible with modern
wire enamels thatoffergood resistance
to
high rates
o f
change
of
voltage.
ynamics
To enable successful designs
to be
completed
in a
timely
and cost-effective
manner,
it is
essential that
capabilities
for computer-modelling
mechanical stress
distribution and
dynamic vibration/resonance/unbalance effects are available. Dynamic studies of the
complete turbine/compressor/alternator assembly,
and
accurate modelling
of
bearing
and
blade contributions to stiffness and damping, form an important component of necessary
technical expertise.
esign
software
Overtheyears, Bowman hasbrought togetheritsaccumulated expertisein PMalternatorand
motor design,
and has
codified this
in a
proprietary, advanced-software design package. This
isa
highly supportive application, which guides
the
user
in the
process
of
entering
raw
data,
preventing
for
example
the
insertion
of
incompatible groups
of
dimensions;
defines the
precise meaning
and
units
of
each displayed item; then draws
a
cross-section
of the
machine
and
computes
a
large
field of
electrical, mechanical,
and
thermal performance parameters.
Alternative materials
may be
selected
for the
laminated core, retaining sleeve, conductor,
coolants, etc.
The workofdeveloping this
software
has been substantial, and was undertaken because no
available
software
couldbe
found
that
offered
either
sufficient
accuracyorversatility.
The softwarehas not
only greatly accelerated
the
design process,
but
because
so
manycases
can be
readily studied,
it
enables
far
more detailed exploration
of
possibilities
and the
development
of
greater intuitive appreciation
of
parameter sensitivities
in
design.
2 3 ecuperators
Durable heat exchangers ofhigheffectivity and low costareneeded toincreasethe efficiency
of
gas
turbines
to the
levels needed
to
compete with reciprocating engine-based power
generation systems. Their function
is to
extract heat
from the
gas-turbine exhaust gases
in
ordertopreheat the airusedin thecombustion process andthereby reduce theamountof fuel
used
to
reach operating temperature.
The
current Bowman recuperator
is a
primary
surface
recuperator (PSR), manufactured
from
stainless steel
for
long
life.
With
an effectivity of
about
90 per
cent,
the fuel
consumption
of the
micro-turbine engine
is
approximately halved, which doubles
the MTG
efficiency from 15 per
cent simple cycle
to about 30 per
cent recuperated cycle.
Refer to
Fig.
1.3.)
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An
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Fig.
1.3
Cyclearrangements
The
majority
of
micro-turbine manufacturers consider stainless steel primary surface
recuperators and users to be the current state of the art, although there are users of an
alternative
recuperator design utilizing brazed plate
and fin
technology.
hi the PSR
design
the
plates
forming
the air and gas
paths
are not
bonded brazed) together.
They
arewelded aroundtheedge,but areclamped together thus allowing movementdue to
thermal
expansion without the high stresses being transmitted to the
joints
as in the brazed
structure.
This
is
considered
to
give potentially higher reliability
and
durability
due to the
lower
potential
for
thermal stress failure
and
consequential leakage.
Refer to
Fig. 1.4.)
Fig 1 4
ecuperators
9
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1
Micro-turbine Generators
further
difference is in the use of annularor box arrangementsto integratet herecuperator
to the gas turbine engine.
Annular
is a
concentric recuperator
that
wraps around
the
engine
and
generally
has all of
the interconnection pipe work as part of the casing.
Box is a cuboid shape that sits outside the engine envelope and requires interface
connection pipework.
There
are
pros
and
cons
for
both types
of
technology
asdetailed
below.
Parameter
Initial development cost
Integration cost
Thermal soak back to
engine coreafter
prolonged operation
Package thermal
management
Package assembly time
Interface issues
ox
Lower
Higher
Noissue
Higher radiated losses requiring
more thermal insulation
and
hence higher cost
Higher
Three more interfaces withengine
and recuperator to consider at
package level-engine casings
have to be manufactured to
reasonable tolerances to
guarantee interchangeability
nnular
Higher
Lower
Potential issue requiring
prolonged shut down
phase to cool recuperator
Lower radiated losses
requiring
less thermal
insulation and lower cost
Lower
Allrecuperator interfaces
are withintheengine,
therefore only one
interface exhaust)
required
to be considered
at
package level
Bowmanhas considered all of the above interface issues at the recuperator design stage, and a
cuboid recuperator, close coupled to the engine, is currently their
preferred
approach. An
example of a cuboid recuperator close coupled to the engine is shown in Fig. 1.5.
Fig 1 5 Cuboid recuperator
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12 Micro turbine Generators
1 2 4 4
Utility
mode operation
The system is capable of operating in parallel with the utility. This mode is particularly cost
effective
as asite s
base load
can be
efficiently supplied while planned long-
or
short-term
overload requirements
are
supported
by the
utility.
1 2 4 4 1
Export
mode
The system can export power to the utility and meets current harmonic limits defined in
specification IEEE 519
2).
1 2 4 4 2 Load following
mode
A
load following mode allows on-site power generation
to be
balanced with site demand
resulting in zero power
flow
to, and in some cases from, the utility. This maximizes the
benefits of embedded generation where no agreement has been made with the utility on
purchase terms for exported power, i.e. the optimum amount of low-cost, embedded
generation is always produced without consuming additional fuel to export power to the
utility.
1 2 4 4 3
Peak shaving mo de
The system can be operated just during times of peak demand, which reduces the tariff paid
by the customer to the utility as this is usually set by his max imu m site dem and.
1 2 4 5 Dual mode switching
Switching between island mode
an d
utility mode operation
is
available
by
means
of a
proprietary switching unit. This enables
the MT G to
serve dual functions
of
prime power
an d
stand-by pow er generator
from one
ratherthan
tw o
systems.
1 2 4 6
Power condit ioningsystem elements
Thepower conditioning system comprizes of a solid-state power converter assembly, power
filter,power controller, andmanagementof the utility interconnection.
A typical systemisshown in Fig. 1.6.
High
efficiency
* IGBT technology
*
Solid
state
high reliability
Aircooled
Programmable voltage/current/
fr qu n y
* Voltage
L-L rm s.) 400-480,
3
phase,
50-60Hz
* Integratedgas
turbine start
facility
Fig.
1.6
Power conditioning units PCUs)
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An
Introduction
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Micro turbine
Generators 13
Thesolid state
power converter consists of rectification, power boost, and inverter stages.
Efficient
power conversion and
effective
thermal management allow
full
power operation
over
a
wide tem perature range.
Bowman
has developed and patented an innovative cooling technique that achieves very
effective
thermal
transferat low
cost.
The power electronic assembly synthesises the high quality output waveform using a pulse
width mod u lating PW M) switching technique.
The
power
filter
efficiently
removes
modulation frequency components from the output
waveform.
Advanced materials are used
for the filter elements in order to minimize power loss and permit operation with severe
electrical loads.
1 2 5 Engine managem ent
and
control
Bowman has over five years experience developing controllers for a variety of micro-turbine
engines. The
features
of the engine controller inclu de:
au tomated start sequence;
batteryoru tility start;
gas orliquidfuel algorithms;
recuperated
or
simple cycle engines;
fault detection
and
protection;
advanced
user
interface.
Thedesign isfully digitalso it has theflexibilityto beadaptedfor arangeo fengine typesand
sizes. Each type of engine has its own
fuel
system, starting characteristics, running speed, etc.,
and all these va riations are accom modated within the same controller.
Digital control also gives precise and repeatable control of engine
speed
and load transients.
Where appropriate the engine controller can also interact with other parts of the generator
control system, for example, by asking for the power output to be reduced if the engine is
running
near its max imu m permitted temperature.
All
the engine systems are monitored to
verify
good health and correct operation. Critical
systems oil pressu re and engine speed) also have additional,
software
independent, backup
monitoring. This data may be
accessed
both locally and remotely, and is used extensively by
the technical and support teams, and is also available to the customer. Special
software
tools
have
been developed in-hou se to assist with the development and proving of engines, starting
algorithms and control algorithms.
Advanced controls already developed include:
constant exhau stgastemperatu re E GT) run ningforoptimu mefficiency an d emissions;
variable speed operationtooptimize
efficiency
andem issionsatpart load;
bypass valve control orvariable heat ou tput;
gassafetymonitor.
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1.2.6
as
boost compressors GBC)
The GBCmust
deliver
natural gas at apressure higher than the airpressure in the MTG s
combustion chamber.Forexample, if the micro-turbine engine s airpressure ratio is4.5, then
the GBC
should
be
capable
of a
pressure ratio slightly over 4.5. Therefore,
a
design pressure
ratioof 5 isassignedto theGBC.
The
efficiency
of the GBC impacts theMTG s overall efficiency. A n increasing GBC power
draw lowers the turbo generator
efficiency.
The MTG s
efficiency
drops sharply when the
GBC efficiency fails
below
0.20, therefore, to enableit to efficiently generate electricity at or
about
thetarget of 30 percent the GBCsystem efficiency must remain well above 0.20.
From
calculations an d test verification, it hasbeen determined that about 2.5 per cent of the
power output of a 50 kW MTG is used to compress the
fuel
gas. This does not take into
account
themotor or coupling efficiency. The electrical-to-mechanical efficiency of a 5 hp
motor
is about 0.80 an d when this is taken into account, the power requirement of the
compressor system is about 1.5 kW.
The MTGmarketwill include power users, such as office buildings, apartment complexes,
an d
small businesses, where minimal involvement in the power source is aprerequisite. A
design
requiring minimal maintenance is consequently needed if the MTG is to be well
received.
Bowman has evaluated tw o types of compressor for usewith its range of MTGs. These are
the sliding vane and the scroll types of
compressor;
the merits of each are discussed as
follows. A typical sliding vane packaged unitisshown in Fig. 1.7.
High reliability
High
efficiency
* Self con tainedpackage
* Compact
*
Low
cost
* Low oil
consumption
* Low maintenance
* Acoustic attenuation
* Easy
installation
Fig
1 7 Gas
boost compressor
2 6 liding vane compressors
Thesearepositive displacement compressors that operate in thefollowing cycle:
gas isdrawn into the suction side andisolated within a chamber;
the gas isthen compressed byreducing thechamber s volume;
gasexitsthe compressor through discharge ports orvalves.
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An Introduction to Micro turbine Generators 15
Sliding vane compressors consist of a rotor, vanes, and a cylindrical easing. The rotor is
mounted eccentrically in the casing. Machined slots in the rotor guide
flat
rectangular vanes.
These vanesa re
free
to move in the slots and are held against the casing by centrifugal force.
As the rotor turns (typically at250-1200 r/min), pockets, which increase then decrease in
volume, are created. Gas is drawn into the expanding pocket and compresses as its volume
decreases. The cross-section of a sliding vane compressor is shown in Fig. 1.8.
ig 1.8 Gasboost compressor GBC)- rotary vane type
Vane
wear is the greatest maintenance concern in sliding vane compressors (not bad though in
flooded types). The vanes remain in contact with the casing a s they wear, bu t eventually they
run
the risk of becoming too short and may break causing damage to the compressor.
Sliding vane compressors are a favoured GBC option because they meet the flow rate and
pressure ratio requirements. In lubricated versions, Pr = 4 may be reached in a single stage. In
addition,
the
discharge
is
nearly pulsation
free,
thereby reducing
or
eliminating
the
need
for
an accumulator tank.
1 2 6 2 croll
type
compressor
The compression cycle
of
scroll compressors
is
less
intuitive
than most other compressor
types. There
are
three main parts
- a
stationary scroll,
an
orbiting scroll,
and a
casing. Both
scrolls are identical, with one rotated 180 degrees out of phase from the other. The orbiting
scroll
is
attached
to an
eccentrically mounted shaft. This shaft orbits
the
moving scroll about
the stationary scroll s centre. A sectional view of a scroll compressor is shown in Fig. 1.9.
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Micro turbine
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ig 1.9 Gas
boost compressor GBC)
scroll type
A
crescent shaped cavity
is formed at the
outside edge
of the
contacting scrolls.
Gas
enters
this cavity through
the
suction port.
As the
moving scroll orbits
the
stationary scroll
the
cavity s size
is
reduced until
it
reaches
the
discharge port
at
their centre.
A
graphic
of
this
motion can be
found
on Copeland Corporation s web page at http://ww w.copelan d corp.
com/airconditioning/scrollintro.html
Scroll compressors have several advantages that enhance their potential
as
suitable micro-
turbinegas
boost compressors:
their volumetric an d isentropic efficiencies are high in fact scroll efficiencies exceed
reciprocating efficiencies;
thereisonlyonemoving part;
theyareavailableforsmall capacities;
there
is no
clearance volume.
Scroll compressors are widely used in refrigeration applications (air conditioners) an d have
recently been converted
to air and gas
compressors. Pressure ratios reach
as
high
as
eight
in a
single stage, while capacities
are low
compared
to
most compressor types. These features
make them suitable for MTG applications.
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An
Introduction
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Micro turbine Generators 17
1 3 Bowmancogeneration CHP)system
The Bowman cogeneration system consists of an MTG integrated with a waste heat recovery
boiler to provide a compact, high
efficiency
low emission, and vibration
free
system
producing heat
and
electrical power.
The
system
is
shown diagrammatically
in
Fig. 1.10.
Fig 1 10 BPS Cogen System
Cogeneration CHP) systems burning natural
gas
incorporate
two key
areas
of
technology:
waste heat recovery boilers;
chillers/refrigeration systems.
High-efficiency
stainless-steel, waste heat boilers have been designed and integrated into the
cogeneration package to enable hot water, typically at 90 C, to be produced
from
the exhaust
gas
stream.
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Micro turbineGenerators
It is
possible
to
produce chilled water
from the
exhaust
heat
through
the use of an
absorption
chiller
driven either directly
from the gas
turbine exhaust stream
or
indirectly
from the hot
waterfrom the
waste heat boiler. Several
of the MT G
manufacturers
are
evaluating alternative
designs
of
chillers
and
alternative chiller suppliers with
an aim of
commercially introducing
a
suitable product
in
2002/3
for air
conditioning applications.
In
order to increase the
efficiency
of the hot water absorption chiller the hot water is produced
at
110 C forthis typeofapplication.
1.4
Benefits
and
advantages
of the
Bowman turbogen
cogeneration product
1.4.1 Recuperated or simple cycle configuration
The micro-turbine engine can be configured in either of the above modes to enable the
cogeneration system
to
best match
the
customers site needs.
The
recuperated machine provides
a
heat
to
power ratio
of
about
2:1 and an
overall system
efficiency ofabout80 per cent. Whereasitehas aneed fo rmore heat up to aheat to power
ratio of 4:1 then a simple cycle system can be installed. In this latter case although the
electrical efficiency naturally falls the overall system efficiency can
rise
to around 90 per
cent. The use of a simple cycle system can be particularly advantageous if it enables a site
boiler to be decommissioned or eliminates the need for a new purchase.
1.4.2 Environmentally friendly
The
Bowman cogeneration system
is
environmentally
friendly in
that
the NOx
emissions
from
the
machine when operating on natural gas are no more than 20 ppm by volume. It is
confidently predicted that this level will
fall to
single digit values within
the
next
one to two
years
and in
factsome machines
are
already achieving this value.
The
design target
for
diesel
and
kerosene
fuels is to
achieve below
25 ppm NOx
although this
is
a
much more challenging target
due to the
more
difficult
atomization
and
combustion process
of
these
fuels
particularly when considering
the low
cost requirement
of the fuel
system.
1.4.3 Fuelflexi ility
Naturalgas is the
primary
fuel of
choice although
the
need
to
burn propane
fuel
light
diesel
and
kerosene
is
essential
to
gain penetration
of
certain markets.
It is now
possible
to
select
engines
to
reliably achieve
effective
combustion
of all
these
fuels.
To expand the market for the micro-turbine product then capability to bum digester gas
landfill gas coal seam gas flare gas and low calorific value man ufactured gas e.g. wood
gasification
gas
is
necessary.
Progress
is
being made
in the
development
of
suitable
combustors
to
enable
all
these gases
to be
burned economically
and
with
low
exhaust
gas
emissions. There
are
several
pilot project
schemes underway
to
address
the
combustion
of all
these gaseous
fuels.
1.4.4 Simplicity of design and operation
There are few moving parts in an MTG system in some cases only the single rotating
element. This naturally leads to a highly reliable system with limited needs fo r routine
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AnIntroductionto Micro turbineGenerators 19
maintenance and low
consumption
of
spare parts. When evaluating through life costs
of a
system
then
these benefits
an d
advantages
are
very significant
in
comparison with
reciprocating engine systems.
A further benefit of
this simplicity
of
design
is the
tremendous potential
fo r
low-cost volume
manufacture. The parts count is dramatically reduced in comparison with alternative
technologies.
1 4 5 Modular design
of
compact size
and low
weight
The
factory
assembled and tested packag e system is easy to install, it s compact size and
low weight being easily handled and requiring little specialist skills to install correctly. The
civil
engineering
costs
are
inexpensive
due to the
small footprint
of the
system
and
also
due to
the fact that the
m achine
is
virtua lly vibration
free.
These
features
no t
only eliminate
the
need
for a
costly foundation block
bu t
also eliminate
the
need
fo r
expensive isolation devices
to
prevent
the transmission of structure borne noise and vibration.
The
standard modular approach
to the
package design allows
the
addition
(o r
removal)
of
further
systems
as an
initial site load grows
or
reduces. Therefore
the
standard range
of
packaged systems allows loads of 30 kW to 1000 kW to be
effectively
addressed both
technically
and comm ercially an d also in a timely convenient m anner.
1 4 6 Modern electrical design
The
use of advanced insulated gate bi-polar technology (IGBT), together with modern
flexible
software
algorithms, allow
the
electrical output
from the
system
to be
selectable
between 380 and 480 volts AC, 3 phase, 50 or 60 Hz frequency to match most of the worlds
low voltage systems.
The standard system has built-in protection fo r under an d over voltage, under and over
frequency,and reverse
power
which a re norm ally required by the utility to allow permission
for parallel operation.
The
widespread dispersal
and
need
for
cost
effective
despatch
and
maintenance necessitates
the supply of a remote control and mon itoring system. A ll Bowman cogeneration systems are
capable of being so monitored and the Customer Support Department uses this tool as a key
elementin the
provision
of a range of support programmes tailored to suit the specific needs
of
it s wide range of customers.
1 5
onclusions
The
micro-turbine industry is rapidly becoming established although the projected high
volume m anufac turing levels are yet to be realized.
There are in 2002,
four
or five companies making commercial shipment of systems
worldwide.
Systems
are
available
from
approximately
30 kW to 150 kW
electrical output,
suitable
for operation on a variety of gaseous and liquid
fuels.
The
distributed power generation market (DG) is being addressed in several key high added
value sectors such as cogeneration and trigeneration, W aste gas utilization, secure pow er, and
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20 Micro-turbine
Generators
mobile power.
As sales
volumes increase then
the MTG
cost will reduce enabling
further
more cost conscious sectors of the DG m arket to be addressed.
The
technology
is
largely proven
and
this C hapter sought
toidentify and
describesome
of the
generic
and
alternative technologies
in
use
There remain several significant regulatory market barriers to be crossed to facilitate
extensive market penetration by small DG systems. For example,accessand connection to the
utility
networks requires new standards and regulations, which recognize the new technology
and
the different way of
doing things. Similarly, there
is
currently little commercial
recognition
of the low
emission
features and
environmental benef its resulting
from the use of
these systems. However, these obstacles
are
being addressed through trade associations
and
by
m anufacturers,
and
will
be
overcome
in due
course.
cknowledgements
ToBowm an Power Systems Limited,
for
giving permission
for
this Chapter
to be
published
eferences
1) EN 50081-1 Electromagnetic Com patibility. General Emission Standard. Residential,
Commercial and
Light industry.
2)
IEEE
519
Recommended practical requirements
fo r
Harmonic Control
in
Electrical
Power Systems.
Bullin
Bowman Power SystemsLimited
Southampton UK
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Micro turbine Generators
Next
Generation
S
L
Hamilton
bstract
Micro turbinegenerators (MTGs) have been
identified
by the US Department ofEnergyas
one of the 27critical technologies for the United States. It hasonly been in the past three
years that MTGs have become commercially available for sale to end users, utilities, and
energy service providers.
Southern California Edison (SCE) has established an MTG testing programme for
manufacturers andothers toevaluatethecertainperformancecapabilitiesof theturbines.The
purpose
of
this programme
is to
provide
an
independent, third-party, testing
assessment
This
projectpurchased, installed, operated,
and
tested micro-turbines
toassess their
performance.
Data
was
collected electronically
and
manually.
This Chapter will discuss
the
next generation
of
MTGs.
2.1
MT S nextgeneration
Recently,
the US
Department
of
Energy (DOE)
has
identifiedturbines
as one of the 27
critical
technologies for the USsecurityandprosperity.Assuchthe DOE
offers funding
for research,
development, anddemonstration (RD D) for MTG and MTGcomponent development, such
as
ceramic materials.
The DOEuses three important criteriatoaward
funding:
1. reduction
of
energy consumption;
2. improvementinenvironmental conditions, suchasemissions; and
3
improvement
in the
overall economics
of the
technology.
2
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22
Micro turbine
Generators
SCE
conducts a unique micro-turbine testing programme for DOE, the California Energy
Commission,
and
EPRI.
The
testing
is at
SCE s
host site. This site
is at the
Combustion
Laboratory at the University of California (UC I) in Irvine, C alifornia. UC I was chosen
because of its robust advanced power programme featuring both an educational and research
facility
built around energy technologies. The programme relies on the National Fuel Cell
Research
Center,
the
world-renowned Combustion Laboratory,
and UCFs
Distributed/Dispersed Energy Technologies programme and demonstration facilities,
including the developm ent of an inverter laboratory, all housed at UC I.
SC E s testing programm e began
in
1996.
It has
tested MTGs
from
Capstone Turbine
Corporation
and
Bowman Power Systems. Until recently,
no
other turbines have been
available for purchase and testing under the programme, although a Honeywell MTG has
arrived for installation and testing. The programme is attempting to purchase and test MTGs
from E lliott E nergy and new models from Capstone.
Our programm e tests the MTGs for machine performance. It tests MTG s performance against
its m anufacturer s performance claims for efficiency, emissions, and noise. MTGs are also
tested against applicable industry standards, such as power quality and/or local requirements,
such
as the
South Coast
Air
Quality Management District s
air
q uality standards.
In
addition,
qualitatively assessed
are the
ease
of MTG
installation
and
startup, maintenance
and
operation,
an d
overall machine performance.
A
daily
log is
m aintained
by the
testing crew
to
ensure the integrity of the testing results and to record events to explain the data captured.
Testing
results include:
Starts stops
Ideally number of planned starts and stops are equal. A variation in the
number of attempted starts without a planned stop indicates that the machine is
experiencing problems.
Overa ll unit efficiency and netpower
output
Based on actual conditions the machine
should provide - a level of
efficiency,
within a small tolerance, as
predicted
by, and
consistent with,
the
derating curves provided
by
m anufacturer.
Operability
Subjective assessment of the mach ine s ease of operation, performance
reliability,
and
consistency,
and its
ease
of
return
to
operations after experiencing
operational problems.
Emission
level
monitoring
Within
a
small tolerance, emissions
are
expected
to be
within
manufacturer s claims for NOx and CO.
Powerquality monitoring
M easures distortion individually for current and voltage. Both
voltage and current distortion should be below the IEEE 519 standards under actual
consistent conditions as described in the standard.
Enduranc e testing- Is a
measure
of
longevity
of the
MTG. Most have
an
advertised
life of
40
000
hours. NREC advertises
80 000
hours.
As a part of the testing programme, SCE has established facilities a t UCI that provide a level
testing field for all MT Gs. MTG s are equipped with data acquisition equipment to ensure
that
data
is
captured
on a
real-time
basis.
A
veteran, on-site, three-person, testing crew also
reviews
the electronic data capture with manual measurements to ensure that electronic
capture is consistent with physical experience.
The
testing crew activity interacts with technical staff
from the
manufacturers.
An
essential
part
of the testing programme is to provide written feedback to each manufacturer, on an
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Micro turbine
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Next
Generation 23
individual basis, about the results of the testing programme. The testing crew offers
suggestions
fo r
con sideration
by the
manufacturer
forfuture
product enhancements.
Another im portant value of the testing programme is that it provides independent, third-party
information
for the public on the perform ance of the MTGs o n a consistent
basis
under actual
operating conditions. 'Lessons learned' offers expert advice on operating experience and
observations that can be used by the public to consider how best to use MTGs under actual
operating conditions.
2.2 The micro turbine technology summit
Toadvance MT G development, the DOE sponsored the micro-turbine technology summit in
December 1998. This summit was intended to
surface
issues so that a
thoughtful
roadmap
would emerge for
focused
an d results-oriented research, development, and demonstration
(RD D). The DOE successfully got valuable ideas and comm ents to help in its efforts to
develop a RD D programme for micro-turbines. Both policy and market-related issues were
necessarily a
major
part of the discussions.
Thesummitidentified thatthemarketfo rMTGsispo tentially quite large but thealternatives
that
are competing to serve industrial power need s will be hard to beat w ith toda y's existing
MTG
technologies. Likewise
the
favorable attributes
of
fuel cells, also
an
emerging
technology, put lots of pressure o n M TGs.
Themajor findingso f the DOEm icro-turbine summ it wereas follows.
Achievingthegoalofincreasingtheoverall efficiency ofmicro-turbinesto 4 percentor
greater could boost the appeal of micro-turbines substantially compared with competing
technolo gies, such
as
diesel gensets.
A number of barriers are
affecting
th e development of marketers fo r small-scale power
plants, including micro-turbines,
not the
least
of
which
is
uncertainty about
the
future
of
thestructure
of
electric power m arkets.
Aparticular issueis theinterconnection of distributed generation technologies, including
micro-turbines, with the utility grid. Interconnection specifications are not standardized
and
vary byutilitysystems across the wo rld.
A
focused RD D programme
can be a
great help
in
improving
th e
prospects
fo r
micro-
turbines.
Low er-cost, moreefficient micro-turbines with known performanceandproven reliability
are
needed.
RD D
to
lower cost
and
increase
the
reliability
of
equipment
fo r fuel
processing,
gas
compression, recuperation, an dpower electronics isalso important.
Development of advanced materials that are less costly, more durable, and capableof
operating
efficiently at
higher temperatures could
be one o f the
keys
to
making substantial
improvements in the thermal
efficiency
and environmental performance of m icro-turbines.
As a result of the summit referenced above, DOE and others have developed funding
solicitationstoprovidefor
future
RD D
funding focused
on thefindings above.
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24
Micro turbine Generators
Based on the findings of the summit, MTGs can be expected to increase
efficiency
through
improved materials.This includes technologies such as ceramics and components like more
efficient
recuperators
and
advanced pow er electronics.
2 3
The next three years
The
next three years will expand existing niches by adding product applications.
MTG manufacturers during the n ext three years will ad d fea tures targeted for expanding their
entry niche markets
and
developing.
This period w ill
focus on
enhancing
the
M TG s capability
in k ey
areas that m ake
it a
broader
based product. These capabilities
are as
follows.
Plug
and
play enhancements will
add to the
user-friendliness
and the MTG
capabilities.
Such ease
of use and
expanded capabilities will
be
advantageous
for
small customers
who
do no t
employ
or
expect
to
employ, highly technical
staff.
These customers will require
that the MTG be
installed simply
and
operated unattended.
The MTG
must
be
smart
enough
to trouble-shoot problems and call home w ith problems. The MTG m ust be able to
configure
itself given the custom er s phy sical requiremen ts and constraints. It should be
ableto
advise
of future
maintenance, such
as
cleaning
filters,
replacement parts,
at
routine
intervals.
Fuel
flexibility
with dual
fuel
capability. MTG s will need
to
operate
efficiently on a
variety
of
fuels,
including natural gas, diesel, propane, digester gas, etc. Most of the m anufactu rers
have
realized
the
value
of
multiple
fuel
operations
and
have designed,
or are
designing,
future
models which
can
operate
on a
variety
of fuels.
Additionally
the M TG
will need
to
have
the
capability
to
switch between
fuel
types
so as to
provide back-up
fueling
capability.
Ideally, these capabilities will be provided transparently to the customer
requiring
only sim ple modifications,
if
any.
Tight, seamless integration to the grid will be important to micro-turbines customer
economics. M TG manu facturers are working with software/firmw are providers to provide
communications and controls that easily provide the ability to aggregate and centrally
dispatch many dispersed MTGs,
if
used
as
standby,
and
other standby distributed
generation
technologies. Small generators located in constrained parts of the grid can be
dispatched and bring needed capacity during peak demand periods when spot prices can
soar.
Environm ental issues related to MTG s surround emission and noise. MTGs areexpected to
be low in NO x but even so, large central plants are catching up so M TGs w ill continue to
push down
the
level
of
NOx. Meanwhile,
low efficiency of
MTGs relative
to
large,
combined-cycle,central plants make reducing M TG green house emissions by increasing
efficiency
a
required
goal.
Most
MTG
m anufacturers claim noise levels
in the 6 570 dB A
at 10 m. In
certain locations, such
as
city
and
urban areas, this level will need
to decline to
55-60
dBA. Also, the high-frequency pitch from the high-speed turbine will require
sattenuation in
some locations
and
some applications.
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Micro turbine Ge nerators
Next Generation
25
2 4 The
next five
to
seven years
For the next five to seven years, MTG manufac turers will add features that expand niches and
attack similar niche opportunities.
Initial niches
for
MTGs
are
commercial customers
who
value increased reliability
due to
significant costs related
to
spoilage
or
lost business.
M TG
manufacturers should look
for the
same type of customer in the industrial sector. To get this larger-size customer, MTGs will
need to be ganged up into multiple-unit packages.
Another attractive niche for M TG s is the customer who uses lots of energy in their p roduction
process and wants to benefit from managing energy price volatility. As electric industry
deregulation continues, rates will mov e toward time-of-use . Under time-of-use pricing,
electricity is priced and sold in discrete blocks of time. During peak periods of the day,
prices
can
escalate. In this instance, the MT G can provide a physical hedg e ag ainst rising prices.
To survive into the next decade, there must be
major
improvement in overall product
robustness and performance so as to grow into broad applications and secure market
acceptance.
2 5 Improvements in the next decade
The most challenging and important aspect of
future
MT Gs will be to
increase
the
efficiency
of the MTG to 40+ per cent without raising the capital
price,
cost of maintenance, or
complicating the operation of the machine. Without this
efficiency
improvement, MTGs will
not be able to compete with emerging
fuel
cells, especially given the added environmental
benefits of
fuel
cells with no emissions and no
noise.
Bibliography
Building
Operating
Management March, 2000, page 12, Outlook, Minipower Plants:
Microturbines Draw Interest
Distributed Generation: U nderstanding the Econom ies , An Arthur D. Little
White
Paper
1999.
Advanced M icroturbines, DOE s Office
of
Industrial Technologies, Energy
Efficiency and
Renewable Energy,
Project
Fact Sheet.
Watts
J. H.
Microturbines: A New Class of Gas Turbine Engine, Global
Gas
Turbine
News Vol . 39: 1999, No 1.
deRouffignac A. Back ing Up the Grid with Microturbines, RDI E nergy Insight December
3, 1999.
Wheat
D. Distributed gen enhances the grid, but can t beat central
power,
P O W E R
November/December 1999.
Swanekamp R . Distributed generation seeks market niches, P O W E R
November/December
1999.
Hamilton S. L. The Buzz is from the Micro Turbine Generators, Deregulation Watch
7.31.99,Vol.
2, No 14.
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26
Micro-turbine Generators
'Distributed
and
Dispersed Energy Resources,
A
Paradigm Shift,' NFCRC Journal,
July/August/September1998, Vol.1,Issue3.
ahl
K. P. and
Hamilton S.
L.
'Microturbines Under
the
Microscope,' Power
Gen
International Conference New
Orleans,
LA
November
30December2
1999.
immer
M. J.
'Distributed generation offers
T D
cost management,' Electric Light
Power,February
2000,
Vol.78, No 2.
S
L
amilton
Southern California Edison USA
StephanieL.Hamilton 2002
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Analysis ofMicro and Mini turbine
Competitive
and
Supply Markets
in
Europe
TShane
bstract
This Chapter provides a summary of research and analysis of the micro- and mini-turbine
market
in Europe, the Middle East, and
Africa
(EMEA). The methodological approach
including
extensive interviewing process is described. The analysis of the results from the
study shows that
the
market
was
origin llyover-hyped
by the
suppliers,
and
that unit sales
have no t reached those early expectations. While market potential exists, some changes in
national provisions (such as in NET
A
or Germany's new CHP Law) are needed to facilitate
market
growth. Market competitors are focused on overcoming key challenges, such as high
kW prices to help drive the market. However, the ratio between electricity and gas prices,
demand for cooling, and the regulatory position of the energy markets will significantly affect
installation potential.
This Ch apter com prises excerpts
from
Frost
&
Sullivan's most recently published analysis
of
the micro- and m ini-turbine market.
3 1 Methodology
The methodological approach applied to the research into the European, Middle Eastern, and
African market
for
micro-
and
mini-turbines (Report
3966-14) followed Frost
&
Sullivan's
twelve-step market engineering research methodology.
The
primary research, analyses,
surveys, comparisons, and forecasts are based on over 100 specific interviews carried out by
experienced analysts plus the results from research undertaken for other related market
analyses.
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28 Micro turbine
Generators
These
100
interviews were conducted with four groups
of
companies, each playing
an
important
part
in
future market development.
1.
Manufacturers
and
developers
of
micro-
and
mini-turbines
and
components (multiple
interviews w ith nine companies).
2.
Packagers/distributors/component suppliers (around 60 interviews).
3. End-users (interviews with nine respondents representing a range of operators).
4.
Electricity
and gas
utilities (around
30
interviews with
Europe s
most important
gas and
electricityutility companies).
The results also draw
on
several years
of
on-going discussions with companies involved
in
supplying
generating sets
and
components
in
Europe
and
North America
as
well
as a
large
number of utility and energy service companies.
The research strategy
was
constructed with
the aim of
providing detailed information
concerning the key
issues
affecting the
market, strategic analysis,
and
specific issue-related
recommendations.
Interviews with manufacturers and developers of micro- and mini-turbines, packagers, and
component suppliers were aimed
at
gaining access
to
information
on
existing
and
planned
products,
company insights,
and
strategies
fo r
growth
and
sales
and
expectations
for
future
markets.
Targeted end-user feedback allowed
an
analysis
of the
market
from
the
bottom
up
providing
key information
such
as
customer attitudes, expectations,
and
experience.
Utility
survey
information
was
conducted aimed
at
providing
a
highly important insight into
the
attitudes
of
utilities towards their utilization
of
micro-
and
mini-turbines
in future
Distributed Generation (DG ) strategies.
3.2
European micro andmini turbine market
The micro-
and
mini-turbine market
in
Europe
is now
developing. Throughout
the
last five
years or so the
mainly
US
manufacturers have been talking
up the
market prospects world-
wide,m aking promises for early delivery o f efficient prime-mover technologies, designed to
revolutionize the Distributed Generation (DG) market. Initial forecasts for thousands of unit
shipments in the
short-term have
no t
been
fulfilled,
although market growth
has
been highly
significant.
Capstoneand E lliott were the first to comm ercialize m icro-turbine units in the U nited States
during
1997. However,
it was not
until 2000 that commercialization
of
micro-turbines took
place
in
Europe, although Kawasaki s
600 kW
mini-turbine
was
launched during 1995 (this
has not
been marketed
for
several years
in
Europe however).
Six
m arket participants
are now
active
in the European sector, offering products that range in output from 30 kW to 600 kW,
although three
new
entrants
are
expected
in the
short-
and
medium-term.
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Analysis of
Micro
andMini turbine
Competitive
and
upplyMarkets
in
Europe
29
During contacts with European energy service companies, and distributed energy studies
undertaken
in the
United States,
it
became evident that many companies anticipate making
multiple
micro-
and
mini-turbine purchases
in the
short-
to
medium-term
as
units become
available,
and
maintenance strategies
and
distribution networks
are
developed. Also,
by
assessingthe market for those primary competing technologies, Frost Sullivan hasbeen
provided with
a
positive view
of the
market
and
expects
it to
develop rapidly during
its
first
years.
Views
regarding
the
primary countries
in
which this technology will
be
significantly adopted
vary.However, the foremost European industrialized nations of Germany, France, Italy, and
the United Kingdom will account for the
majority
of units. However, the ratio between
electricity
and gas
prices, demand
for CHP or
air-conditioning,
and the
regulatory position
of
the energy market in each country, will significantly effect installation potential in all
European countries.
3 2 1 1 Market
efinitions
3 2 1 1
Micro turbines
Most micro-turbines are based on technologies that were originally developed for use in
auxiliary power systems,
aircraft or
automotive turbochargers. Most
are
small, recuperated,
or
regenerated high-speed combustion turbines that range from 20 kW to 500 kW intotal power
output
and
have
one
moving part. This comprises
a
high-speed rotating
shaft
that includes
the
compressor, turbine wheel, and generator. In some cases, the shaft is mounted on air bearings
rather than lubricated bearings, which
are
commonly used
in
conventional turbines.
3 2 1 2
Mini turbines
Mini-turbines are generally based on traditional axial gas-turbine technology and are
essentially
a
scaled-down version
of
such.
For the
purposes
of
this study
Frost
Sullivan
has
excluded units with
an
output above
600 kW
based
on the
idea that they
are not
competing
within
the
same output range bracket
and the
market
for
larger units inhabits
a
relatively older
product life-cycle stage. However, mini-turbinesaregenerallyanon-viable proposition below
around 400 kW because of performance compromises for lower output configurations.
Several original equipment manufacturer (OEM) companies have this typeof turbineon the
market
or in the
latter stages
of
development, including Volvo Aero Turbines, Kawasaki
Gas
Turbine and
OPRA (using radial-flow technology).
3 2 1 3 roduct features
The
adoption
of a
high-speed generator
and a
minimal number
of
moving parts provides
a
number of beneficial features. For example, the set-up eliminates the need for a gearbox.
Some players, however, such
as
Ingersoll-Rand s PowerWorks
andOPRA's
Trial Units, adopt
gearbox systems.Inaddition, micro-andmini-turbinesarehighlyreliableandrequireamuch
reduced maintenance schedule that
is
understood
to
vary from between 8000 hours (for air-
filter replacement),
to 16 000
hours (thermocouple replacement),
to 30 000
hours (for turbine
hardware replacement).
The
systems
run on a
range
of fuels
consisting
of
natural
and
othergases,such
as landfill and
sour gas, diesel, and
liquefied
petroleumgas (LPG). Emissions have provedto be relatively
low, co
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