Micro Turbine Generating System

7/30/2019 Micro Turbine Generating System

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MICROTURBINE GENERATOR SYSTEM

Presented by

N.MAHESH09261A0240

E.E.E , B.TECH

MGIT,GANDIPET

MOBILE NO:7416380626

[email protected]

P.R.S.C .Dheekshith

09261A0245

E.E.E ,B.TECH

MGIT,GANDIPET

MOBILE NO:9032726857

[email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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ABSTRACT:

The Turbine Generating Systems

presents us a idea of generating stations using vast

land and human resources to produce power

.Generally turbines occupies a large area and a

specified location ,and it requires large

infrastructure. The main disadvantage of Turbine

generating system is that it cannot be located in a

highly populated area. Many of the disadvantages

of Turbine generating systems can be resolved in

MICROTURBINE GENERATING SYSTEM.

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".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 arefrigerator. The engine itself is about the size of a

beer keg . 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.

Microturbines are the systems which can belocated even in a small location.

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 startermotor. Microturbine generating systems found

their applications in Co-generation , Distributed

power generation,Backup generators , Indoor pool

, Hybrid vehicles etc.

INTRODUCTION:

Microturbines are the new

type of combustion turbines 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 directmechanical drive markets such as compression and

air conditioning. Microturbines have installed with

considerable success in office and apartment


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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.

WHAT IS MICROTURBINE ?

Microturbinesare 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. Themost 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 the turbine turning at highrpm, 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 ofmoving 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%.

There is very definitely a trend

toward installing microturbine system onsitenotonly 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 system. The core idea is this: when burning

a fuel in a micro turbine unit, dont 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. Dont waste

that valuable energy to the atmospherewhich is

what they do in most central power plants .

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 combined

heat and power(CHP) 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 , with CHP one would be using

65% or more of the fuels thermal energy.

The 30-kilowatt model of

Microturbine is very versatile, being able to burn

several gaseous or liquid fuelsnatural gas,

propane, biogas, diesel, and kerosene.

Microturbine Overview

Commercial Available - Yes (limited)

Size Range - 25-500 kW


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Fuel - Natural gas,

hydrogen, propane, and diesel.

Efficiency - 20-30%

(recuperated)

Environmental - low (


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turning on the single turbo-compressor shaft or

with a separate power turbine driving a gearbox

and conventional 3,600 rpm generator. The high-

speed generator of the single-shaft design employs

permanent magnet 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 (blackstarting), 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 1,200F)to preheat the compressed air

(typically around 300F) 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 turbines effectiveness

in CHP applications.

BEARINGS:

Microturbines 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 nevercomes 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 bearingshave been in

service on airplane cabin cooling systems for many

years. They allow the turbine to spin on a thin layerof 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 significant experience with substantial


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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 remotemonitoring and operation.

HOW MICROTURBINE WORKS?

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.

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 theelectric 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 airthis 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 revolutionsper 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

turbinein 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

3have lower efficiencies at around 15%, but

also lower capital costs, higher reliability,

and more heat available for cogeneration

application than recuperated unit.

Recuperated

microturbinesrecuperated 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-conversionefficiencies 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

MICROTURBINES:

Some of primary applications for microturbineinclude:

GeneratorCoolingFins

CombustionChamb

er

ExhaustOutlet

Recuperator

AirBearing

s

Compressor

Generator

Turbine


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Distributed generationstand alone, on

site applications remote from power grids.

Quality power and reliabilityreduced

frequency variation, voltage transients,

surges, dips, or other disruptions.

Stand by powerused in the event of an

outage, as back up to electric grid.

Peak shavingthe use of microturbines

during times when electric use and demand

charges are high.

Boost powerboost localized generation

capacity and on more remote grids.

Low cost energythe 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.

Advantages of Distributed Generation:

As energy need not be

transmitted there is no need of any largetransmission 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 companys 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

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 isgenerated locally to meet demand in the local area,

for example a small towns electricity supply. This

can relieve congestion of the distribution network


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or power grid. Hospitals, hotels, factories and

holiday resorts can install distributed power at

remote sites without grid access.

Distributed generation provides a

wide range of services to consumers and utilities,

including standby generation, peak shavingcapability, base load generation and co-generation.

Hospitals

The 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 generators

Microturbines 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

gaswells.

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


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close to the point of use and the clean emissions.

Vehicle applications

Hybrid vehicle( microturbine to high speedalternator)

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 cellscan 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

Microturbin

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

These costs include all hardware, associatedmanuals, 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 unitscan provide higher reliability than conventional

reciprocating generating technologies.

Manufacturers expect that initial units will require


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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 COST

Capital cost $700-$1100\Kw

O&M Cost $0.005-0.016\kw

Maintenance Interval 5,000-8,000hrs

ADVANCED MICROTURBINE PROGRAM

The Advanced Microturbine

Program is a six-year program for FY 2000-2006

with a Government is investment of over $60

Million. End-use 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 MANUFACTURERS

The leading microturbine manufacturers are

1. Bowman power systems

2. Capstone Turbine Cooperation

3. Elliott energy systems

4. Turbec AB

5. Ingersoll-Rand Company

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 andidentifying 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


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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.

Documents

Micro Turbine Generating System