GOVERNMENT OF KERALA - 123seminarsonly.com · Web viewengines, it is believed that there liability of such a lubrication system is more typical of ship propulsion diesel systems (which

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SEMINAR REPORT

MICROTURBINE GENERATOR

SYSTEM By MOHAMMED SHOAIB

1NH07EE023

New horizon College of engineering Dept. of Electrical and electronics Engineering

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ACKNOWLEDGEMENT

The satisfaction and euphoria that accompany the successful

completion of any task would be, but impossible without the mention of the people

who made it possible, whose constant guidance and encouragement crowned my

accomplishment.

I would like to record here the constant encouragement and facilities

extended to me by Prof. K.N.BHANUPRAKASH, Professor and head of the

department of Electrical and Electronics, NHCE.I extend my sincere gratitude to

him.

I express my gratitude to Mrs. GAYATHRI SHIVAKUMAR, my

class teacher and also Mr. MAHESH.K, senior lectures for constantly monitoring

the development of the seminar and setting up precise deadlines. Their valuable

suggestions were the motivation factors in completing the work.

I also thank all the staff members of Electrical and Electronics

department for their whole hearted co operation extended to me.


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ABSTRACT

MICROTURBINES are becoming wide spread for distributed power

and combined heat and power applications. They range from handheld units

producing less than a kilowatt to commercial sized systems that produce tens or

hundreds of kilowatts. They are also known as "turbo alternators", or "gensets".

Part of their success is due to advances in electronics, which allow unattended

operation and interfacing with the commercial power grid. Electronic power

switching technology eliminates the need for the generator to be synchronized

with the power grid. This allows, for example, the generator to be integrated with

the turbine shaft, and to double as the starter motor. Microturbine systems have

many advantages over piston engine generators, such as higher power density

(with respect to footprint and weight), extremely low emissions and few, or just

one, moving part. They accept most commercial fuels, such as natural gas,

propane, diesel and kerosene. They are also able to produce renewable energy

when fueled with biogas from landfills and sewage treatment plants. Microturbine

designs usually consist of a single stage radial compressor, a single stage radial

turbine and a recuperator.Typical micro turbine efficiencies are 25 to 35 percent.

When in a combined heat and power cogeneration system, efficiencies of greater

than 80 percent are commonly achieved.


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CONTENT

Introduction 5

What is a micro-turbine 6 Micro-turbine overview 8 Basic components of micro-turbine 8 Working 13 Types of micro-turbine 16 Characteristics of micro-turbine 17 Distributed energy generation 18 Strength 19 Weakness 19 Applications of micro-turbines 19 Economics of micro-turbine. 24 Advanced micro-turbine program 25 Micro-turbine manufactures 26 Conclusion 27

References 29


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INTRODUCTION

Microturbines are a new type of combustion turbine being used for

stationary energy generation applications. They are small combustion turbines,

approximately the size of a refrigerator, with outputs of 25kw to 500kw, and can

be located on sites with space limitation for power production. Microturbines are

composed of a compressor, combustor, turbine, alternator, recuperator, and

generator. Waste heat recovery can be used in combined heat and power system to

achieve energy efficiency levels greater than 80%. In addition to power generation

micro turbines offer an efficient and clean solution to direct mechanical drive

markets such as compression and air conditioning. Since making their commercial

debut a mere five years ago, microturbines have installed with considerable

success in office and apartment building, hotels and motels. Supermarkets, school

and college, office and industrial parks, small industries, and numerous other

facilities both in the US and abroard.They provide not only electricity, but the

thermal energy to provide for all heating and cooling needs.


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WHAT IS A MICROTURBINE?

Microturbines are small combustion turbines approximately the size

of a refrigerator with outputs of 25kw to 500kw. They evolved from automotive

and truck turbochargers, auxiliary power units for airplanes, and small jet engines

and are comprised of a compressor, combustor, turbine, alternator, recuperator,

and a refrigerator. The engine itself is about the size of a beer keg. The most

popular models have just one moving parts—a shaft with a turbine wheel on one

end , a permanent magnet generator on other end, and an air compressor wheel in

the middle. This assembly rotates at up to 96,000 rpm. At that speed, traditional

oil-lubricated bearings are severely challenged. Accordingly the most popular

micro turbine engines use air bearing to float the shaft.

Not only is the turbine turning at high rpm, so is the generator. The

generator in turn produces a high frequency electrical output, which is then

converted by power electronics unit to grid –compatible 400-to-480-volts

alternating current, 10-to-60 hertz.3phase power.

Microturbine offer a number of potential advantages compared to

other technologies for small-scale power generation. These advantages include a

small number of moving parts, compact size, light-weight, greater efficiency,

lower emission, lower electricity cost, and opportunities to utilize waste fuels.

They have the potential to be located on sites with space limitation for the

production of power. Waste heat recovery can be used with these systems to

achieve efficiencies greater than 80%.


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Ther

e is very definitely a trend toward installing microturbine system onsite—not only

for generating electric power. But also for meeting site heating and cooling needs.

Such microturbine configuration are called combined heat and power, or combined

cooling, heat and power (cogeneration) system. The core idea is this: when

burning a fuel in a micro turbine unit, don’t just use the resulting heated gases to

spin a turbine and generate electricity. There is still a huge amount of thermal

energy in the turbine exhaust. Don’t waste that valuable energy to the atmosphere

—which is what they do in most central power plants (because there is no use for

the heat in remote areas).

Instead, use a heat exchanger to capture much of that thermal energy

and use it to meet all the heating and cooling needs of the site. When a

microturbine unit is arranged in CHP or CCHP mode, heat from the turbine stack

is captured and used to meet some or all the heating and cooling needs of the

facility. This makes for much more efficient fuel use. Instead of just using 35% of

thermal energy released during fuel combustion (as with a traditional central

power plant), with CHP and CCHP one would be using 65% or more of the fuels

thermal energy. This realization is a major reason the federal Department of

Energy has been strongly encouraging the advance of onsite power generation

with CHP and CCHP.

The 30-kilowatt model of Microturbine is very versatile, being able to burn several

gaseous or liquid fuels—natural gas, propane, biogas, diesel, and kerosene.


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Microturbine Overview

Commercial Available - Yes (limited)

Size Range - 25-500 kW

Fuel - Natural gas, hydrogen, propane, and diesel.

Efficiency - 20-30% (recuperated)

Environmental - low (<9-50 ppm) NOx

Other features - Cogeneration (50-80 C water)

Commercial Status - Small volume production, commercial

prototypes.

BASIC COMPONENTS OF MICROTURBINE


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TURBO COMPRESSOR:-

The basic components of a microturbine are the compressor, turbine generator, and

recuperator. The heart of the microturbine is the compressor-turbine package,

which is commonly mounted on a single shaft along with the electric generator.

Two bearings support the Microturbines Single shaft. The single moving part of

the one-shaft design has the potential for reducing maintenance needs and

enhancing overall reliability. There are also two-shaft versions, in which the

turbine on the first shaft directly drives the compressor while a power turbine on

the second shaft drives a gearbox and conventional electrical generator producing

60 Hz power. The two shaft design features more moving parts but does not

require complicated power electronics to convert high frequency AC power output


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to 60 Hz. Moderate to large-size gas turbines use multi-stage axial flow turbines

and compressors, in which the gas flows along the axis of the shaft and is

compressed and expanded in multiple stages. However, micro turbine turbo

machinery is based on single-stage radial flow compressors and turbines. Radial

flow turbo machinery handles the small volumetric flows of air and combustion

products with reasonably high component efficiency.1 Large-size axial flow

turbines and compressors are typically more efficient than radial flow components.

However, in the size range of microturbines -- 0.5 to 5 lbs/second of air/gas flow --

radial flow components offer minimum surface and end wall losses and provide

the highest efficiency. In micro turbines, the turbo compressor shaft generally

turns at high rotational speed, about96, 000 rpm in the case of a 30 kW machine

and about 80,000 rpm in a 75 kW machine. One 45kW model on the market turns

at 116,000 rpm. There is no single rotational speed-power size rule,

as the specific turbine and compressor design characteristics strongly influence the

physical size

of components and consequently rotational speed. For a specific aerodynamic

design, as the power rating decreases, the shaft speed increases, hence the high

shaft speed of the small micro turbines.

GENERATOR:-

The microturbine produces electrical power either via a high-speed

generator turning on the single turbo-compressor shaft or with a separate power


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turbine driving a gearbox and conventional 3,600 rpm generator. The high-speed

generator of the single-shaft design employs permanent magnet (typically

Samarium-Cobalt) alternator, and requires that the high frequency output (about

1,600 Hz for a 30 kW machine) be converted to 60 Hz for general use. This power

conditioning involves rectifying the high frequency AC to DC, and then inverting

the DC to 60 Hz AC. Power conversion comes with an efficiency penalty

(approximately five percent).To start-up a single shaft design, the generator acts as

a motor turning the turbo-compressor shaft until sufficient rpm is reached to start

the combustor. Full start-up requires several minutes. If the system is operating

independent of the grid (black starting), a power storage unit (typically battery

UPS) is used to power the generator for start-up.

RECUPERATOR:-

Recuperators are heat exchangers that use the hot turbine exhaust

gas (typically around 1,200ºF)to preheat the compressed air (typically around

300ºF) going into the combustor, thereby reducing the fuel needed to heat the

compressed air to turbine inlet temperature. Depending onmicroturbine operating

parameters, recuperators can more than double machine efficiency. However,

since there is increased pressure drop in both the compressed air and turbine

exhaust sides of the recuperator, power output typically declines 10 to 15% from

that attainable without the recuperator. Recuperators also lower the temperature of

the micro turbine exhaust, reducing the micro turbine’s effectiveness in CHP

applications.


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BEARINGS:-

Microturbine

s operate on either oil-lubricated or air bearings, which support the shaft(s). Oil

lubricated bearings are mechanical bearings and come in three main forms – high-

speed metal roller, floating sleeve, and ceramic surface. The latter typically offer

the most attractive benefits in terms of life, operating temperature, and lubricant

flow. While they are a well-established technology, they require an oil pump, oil

filtering system, and liquid cooling that add tomicroturbine cost and maintenance.

In addition, the exhaust from machines featuring oil lubricated bearings may not

be useable for direct space heating in cogeneration configurations due to the

potential for contamination. Since the oil never comes in direct contact with hot

combustion products, as is the case in small reciprocating

engines, it is believed that there liability of such a lubrication system

is more typical of ship propulsion diesel systems (which have separate bearings

and cylinder lubrication systems) and automotive transmissions than cylinder

lubrication in automotive engines.. Air bearings have been in service on airplane

cabin cooling systems for many years. They allow the turbine to spin on a thin

layer of air, so friction is low and rpm is high. No oil or oil pump is needed. Air

bearings offer simplicity of operation without the cost, reliability concerns,

maintenance requirements, or power drain of an oil supply and filtering system.

Concern does exist for the reliability of air bearings under numerous and repeated

starts due to metal on metal friction during startup, shutdown, and load changes.

Reliability depends largely on individual manufacturers' quality control

methodology more than on design engineering, and will only be proven after


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significant experience with substantial numbers of units with long numbers of

operating hours and on/off cycles.

POWER ELECTRONICS:-

As discussed, single-shaft micro turbines feature digital power

controllers to convert the high frequency AC power produced by the generator

into usable electricity. The high frequency AC is rectified to DC, inverted back

to 60 or 50 Hz AC, and then filtered to reduce harmonic distortion. This is a

critical component in the single-shaft microturbine design and represents

significant design challenges, specifically in matching turbine output to the

required load. To allow for transients and voltage spikes, power electronics

designs are generally able to handle seven times the nominal voltage. Most

microturbine power electronics are generating three phase electricity. Electronic

components also direct all of the operating and startup functions.

Microturbines are generally equipped with controls that allow the unit to be

operated in parallel or independent of

The grid, and internally incorporate many of the grid and system protection

features required for interconnect. The controls also allow for remote monitoring

and operation.

HOW MICROTURBINE WORKS?


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Microturbine engine has only one moving part, basically a shaft. At

one end of that shaft is a turbine wheel; at the opposite end of the shaft is a

permanent magnet electric generator; and positioned at the mid point of that shaft

is an air impeller wheel (ie; an air compressor) for drawing ambient air ,

compressing it , then pumping it into combustor. Fuel is then injected into the

combustor, where it then mixes with compressed air. Combustion occurs and the

resulting gasses expand and rush out through the turbine, spinning it to a very high

rpm.


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This whole microturbine system is packaged in an enclosure not much bigger than

a refrigerator—about 7 feet tall, 2.5 feet wide and 6.5 feet deep. Ambient air is

first drawn into the microturbine system enclosure, filtered, then passed over the

electric generator, which is kept cool by this passing air. Next, the air is drawn into

the impeller (or compressor), which compresses the air before pumping it into the

combustor

SCHEMATIC DIAGRAM OF RECUPERATED TYPE MICROTURBINE


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Now, a part of that compressed –air stream exiting the impeller (compressor) is

diverted to the air bearing. The microturbine shaft in effect now rides on a thin

film of compressed air—this being in the thin annular space between the rotating

shaft and the stationary bearing housing

TYPES OF MICROTURBINE

Microturbine are classified by the physical arrangement of the component

parts; single Shaft, simple cycle, or recuperated, inter-cooled, and reheat. The

machines generally rotate over 40000 revolutions per minute. The bearing

selection –oil or air- is dependent on usage .A single shaft microturbine with

high rotating speeds of 90000 to 120,000 revolutions per minute is the more

common design ,as it is simpler and less expensive to built. Conversely, the spilt

shaft is necessary for machine drive applications, which does not require an

inverter to change the frequency of the AC power.

Microturbine generator can also be divided into two general classes:

Unrecuperated (simple cycle) micro turbine—in a simple

cycle, or unrecuperated, turbine. Compressed air is mixed with fuel and

burned under constant pressure condition. The resulting hot gas is allowed

to expand through a turbine to perform work. Simple cycle microturbines

have lower efficiencies at around 15%, but also lower capital costs, higher


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reliability, and more heat available for cogeneration application than

recuperated unit.

Recuperated microturbines—recuperated units use a sheet metal

heat exchanger that recovers some of the heat from an exhaust stream and

transfers it to the combustor. Further exhaust heat recovery can be used in a

cogeneration configuration. The figures below illustrate a recuperated

microturbine system. The fuel-energy-to electrical-conversion efficiencies

are in the range of 20 to 30%. In addition, recuperated units can produce 30

to 40% fuel savings from preheating.

Recuperated Microturbine

CHARACTERITICS OF MICROTURBINESSome of primary applications for microturbine include:


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Distributed generation—stand –alone, on site applications remote from

power grids.

Quality power and reliability—reduced frequency variation, voltage

transients, surges, dips, or other disruptions.

Stand by power—used in the event of an outage, as back up to electric grid.

Peak shaving—the use of microturbines during times when electric use and

demand charges are high.

Boost power—boost localized generation capacity and on more remote

grids.

Low cost energy—the use of microturbines as base load primary power that

is less expensive to produce locally than it is to produce from the electric

utility

Combined heat and power (cogeneration )—increase the efficiency of on-

site power generation by using the waste heat for existing thermal process.

DISTRIBUTED ENERGY GENERATION

Energy is produced on a large scale in large thermal and hydro

electric power plants and is then distributed to the users through network of lines

called the power grid. These plants meet the need of consumers over a large area.

In distributed energy generation on the other hand involves the on site generation

of small scale power. On-site power generation means power is generated right

where it is needed.


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Advantages of Distributed Generation

As energy need not be transmitted there is no need of any large

transmission infrastructure. Thus the losses during power transmission are

greatly reduced. The combined heat and power (CHP) technology can be

applied to micro turbines to increase its efficiency. This lowers emission and

operating cost by reducing losses and increasing efficiency. From a company’s

point of view, it gives greater control, choice and flexibility in meeting needs

for power and heat energy.

Selected strength and weaknesses of microturbine technology are:

Strengths

Small number of moving parts

Compact size

Lightweight

Good efficiencies in cogeneration

Low emission

Can utilize waste fuels

Long maintenance interval

No vibration

Less noise than reciprocating engines

Weaknesses Low fuel to electricity efficiencies


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Loss of power output and efficiency with higher ambient temperature and

elevation.

APPLICATIONS OF MICROTURBINES

Microturbines are being increasingly preferred over reciprocating

engines in many applications. These include:

Combined heat and power (co-generation)Waste heat from the micro turbine can be transferred via a heat

exchanger to produce steam or provide hot water for local area. The hot water can

be used in a green house to grow plants; water can duct to provide central heating

in building in winter. Thermal hosts can found easier because the the produced by

each microturbine unit is so much that by a large power station.

Distributed power generation

Electricity is generated locally to meet demand in the local area, for

example a small town’s electricity supply. This can relieve congestion of the

distribution network or power grid. Hospitals, hotels, factories and holiday resorts

can install distributed power at remote sites without grid access.


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Distributed generation provides a wide range of services to

consumers and utilities, including standby generation, peak shaving capability,

base load generation and co-generation.

HospitalsThe waste heat from the generator can be used to create for the

sterilization of medical equipment as well as for laundry purposes, like the daily

changing of bed linen. It can also act as backup power supply, which is critical for

the smooth functioning of various life-supporting equipments.

Backup generatorsMicroturbines can also be used in remote areas where there is no

access to electricity. It could provide electricity for research station in the middle

of a jungle or desert, where there is no ready access to diesel supplies but is

located near gas wells.


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Indoor pool

The indoor pool, which contains 200,000 gallons of water and a dive pool containing 250,000 gallons of water. Before the DG installation, all heat was provided by steam purchased from the CU Power House, located on campus. A large heat exchanger is in place below ground on the west side of the building. Temperature sensors monitored the pool water and steam was metered in as needed to maintain the desired temperature. The pools are used year round and need to be maintained at a temperature of about 81° F.

Tabrizi cited several factors that made this microturbine a desirable choice for installation at the Recreation Center pool. These include the small footprint, high efficiency, combined heat and power availability, the ability to locate the unit close to the point of use and the clean emissions.


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Generating electricity with coal mine methane fueled microturbines

Five Capstones Micro Turbines Operating at abandoned Akabira Mine in Japan

A large portion of the methane emitted from coal mines comes from gob areas (collapsed rock over mined-out coal), where methane concentrations may vary from 30 to 80%. Coal mines frequently do not use medium-quality gas from gob wells and instead vent the gas to the atmosphere, contributing to global warming. However, gas with a methane concentration exceeding 35% can in fact be used as a fuel for on-site power generation. Given their large energy requirements, coal mines can recover methane and generate electricity with micro turbines to realize significant economic savings and reduce greenhouse gas emissions. The micro turbine is advanced technology developed from the defense industry that may be an ideal option for on-site electricity generation at coal mines. The micro turbine consists of a small, air-cooled gas turbine connected to a high- speed generator and compressor on a single shaft. This simple design results in a system with a high power output, minimal noise generation, and efficient operation. Diesel, gasoline or kerosene can be used as alternate fuels to insure continuous electricity production in the event that the methane supply is disrupted.


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Vehicle applications

Hybrid vehicle( microturbine to high speed alternator)

In hybrid vehicle applications, the power produced by a microturbine is converted

into electricity by a high –speed alternator. The power is used to drive electric

motors connected to the wheels. Any excess energy is directed to an energy

storage system such as batteries or flywheels. The operating mode of the hybrid

approaches ranges from battery-primary systems where the microturbine can be a

‘battery charger’, to engine-primary system where the batteries help the micro

turbine meet peak power needs, e.g. during acceleration.

Hybrid vehicle (microturbine and fuel cell together)A hybrid combination of micro turbines with fuel cells can increase overall

system efficiencies. Hybrid systems take advantage of an increase in fuel cell

efficiency with an increase in operating pressure. The microturbine compressor

stage is used to provide this pressure. The fuel cell produces heat along with

power, and this heat energy is used to drive the microturbines turbine stage. If

the fuel cell produces enough heat the micro turbine can generate additional

power. For the hybrid combination, efficiency is expected to be as much as

60% and emission less than 1.0 ppm NOx, with negligible SOx and other

application.

ECONOMICS OF MICROTURBINES


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Microturbine capital costs ranges from $700 -$1,100\kW. These

costs include all hardware, associated manuals, software, and initial training.

Adding heat recovery increases the cost by $75-$350\kW.

Installation costs very significantly by location but generally add 30-50%to the

total installed cost.

Microturbine manufacturers are targeting a future cost below $650\kW. This

appears to be feasible if the market expands and sales volumes increase.

With fewer moving parts, microturbine vendors hope the units can provide higher

reliability than conventional reciprocating generating technologies. Manufacturers

expect that initial units will require more unexpected visits, but as the products

mature, once-a- year maintenance schedule should suffice. Most manufacturers are

targeting maintenance intervals of 5,000-8,000 hours.

Maintenance costs for micro turbine units are still based on forecasts

with minimal real-life situation. Estimates range from $0.005-$0.016 per kWh,

which would be comparable to that for small reciprocating engine systems.

MICROTURBINE COSTCapital cost $700-$1100\Kw

O&M Cost $0.005-0.016\kw

Maintenance Interval 5,000-8,000hrs

ADVANCED MICROTURBINE PROGRAMThe Advanced Microturbine Program is a six-year program for FY

2000-2006 with a Government is investment of over $60 Million. End-use


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applications for the program are open and include stationary power applications in

industrial, commercial, and institutional sectors. The program includes

competitive solicitation (s) for engine conceptual design, and sensors

and controls. Technology evaluations and demonstrations are also part of the

program.Planned activities for this program focus on the following performance

targets for the next generation of “ultra-lean, high efficiency” microturbine

product design:

High efficiency: Fuel- electricity conversion efficiency of at least 40%.

Environment : NOx< 7ppm (natural gas)

Durability: 11,000 hrs of reliable operation between major overhauls and

a service life of at least 45,000 hrs.

Cost of power: System costs< $500/kW, costs of electricity that are

competitive with the alternatives (including grid) for market applications.

Fuel flexibility: Options for using for using multiple fuels including

diesel, ethanol, landfill gas, and bio-fuels.

MICROTURBINE MANUFACTURERSThe leading microturbine manufacturers are

1. Bowman power systems

2. Capstone Turbine Cooperation

3. Elliott energy systems

4. Turbec AB

5. Ingersoll-Rand Company


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CONCLUSION

Micro-turbines and miniature thermal devices pose unique challenges and

opportunities for combustion in small volume. The principal difficulties are

associated with limited residual time and heat transfer losses due to high surface to

volume ratio. This paper addresses a preliminary analysis of Micro-turbine .The

micro-turbine is in early stages of pre-production and is still in the developmental

phase .The coupling of micro-turbine with a high temperature fuel cell (SOFC –

solid oxide fuel cell) is one of them .If the waste heat is used the overall fuel

utilization efficiency can be increased. Major features, parameters and

performance of the micro-turbine are discussed here. Fully understanding these

and identifying the solutions, it is key to the future establishing of an optimum

overall system. In the case of the micro-turbine changes will be minor as they

enter production on a large scale within the next year or so, there is an extensive

efforts are expanded to reduce unit cost .It is reasonable to project that a high

performance and cost effective hybrid plant, with high reliability, will be ready for

commercial service in the middle of the first decade of the twenty century


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1.


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REFERERENCES

http://www.wbdg.org/design/microturbines.php

http://www.microturbine.com/Documents/WCEMC04.pdf

http://www.epri.com/

http://www.asme.org/igti/resources/ articles/microturbines

http://www.rmotc.com/pdfs/96ec2.pdf

http://www.drykiln2000.com/

http://www.turbec.com/energy/the_microturbine.htm

http://www.energy.ca.gov/distgen/equipment/microturbines
