1 Training Session on Energy Equipment Cogeneration Presentation from the “Energy Efficiency Guide for Industry in Asia”

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Training Session on Energy Training Session on Energy EquipmentEquipment

CogenerationCogeneration

Presentation from the

“Energy Efficiency Guide for Industry in Asia”

www.energyefficiency.asia.org

© UNEP 2006© UNEP 2006

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Training Agenda: CogenerationTraining Agenda: Cogeneration

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Introduction

Types of cogeneration systems

Assessment of cogeneration systems

Energy efficiency opportunities

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IntroductionIntroduction

• Generation of multiple forms of energy in one system: heat and power

• Defined by its “prime movers”• Reciprocating engines• Combustion or gas turbines, • Steam turbines• Microturbines• Fuel cells

What’s a Cogeneration/CHP System?Ther m

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Efficiency Advantage of CHPTher m

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Uni ts

34

Uni ts

6 Units (Losses)

60

40

36 Units (Losses)

= 85%

= 40%

10 Units (Losses)

Conventional Generation (58% Overall Efficiency)

Combined Heat & Power (85% Overall Efficiency)

(UNESCAP, 2004)

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• Increased efficiency of energy conversion and use

• Lower emissions, especially CO2

• Ability to use waste materials

• Large cost savings

• Opportunity to decentralize the electricity generation

• Promoting liberalization in energy markets

Benefits of Cogeneration / CHP)Ther m

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Introduction




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Type of Cogeneration SystemsType of Cogeneration Systems

• Steam turbine

• Gas turbine

• Reciprocating engine

• Other classifications:

- Topping cycle

- Bottoming cycle

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• Widely used in CHP applications

• Oldest prime mover technology

• Capacities: 50 kW to hundreds of MWs

• Thermodynamic cycle is the “Rankin cycle” that uses a boiler

• Most common types• Back pressure steam turbine• Extraction condensing steam turbine

Steam Turbine Cogeneration SystemTher m

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• Steam exits the turbine at a higher pressure that the atmospheric

Back Pressure Steam TurbineTher m

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Fuel

Figure: Back pressure steam turbine

Advantages:-Simple configuration-Low capital cost-Low need of cooling water -High total efficiency

Disadvantages:-Larger steam turbine-Electrical load and output can not be matched

Boiler Turbine

Process

HP Steam

Condensate LP Steam


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• Steam obtained by extraction from an intermediate stage

• Remaining steam is exhausted

• Relatively high capital cost, lower total efficiency

• Control of electrical power independent of thermal load

Extraction Condensing Steam Turbine

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Boiler Turbine

Process

HP Steam

LP SteamCondensate

Condenser

Fuel

Figure: Extraction condensing steam turbine


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• Operate on thermodynamic “Brayton cycle”• atmospheric air compressed, heated,

expanded• excess power used to produce power

• Natural gas is most common fuel

• 1MW to 100 MW range

• Rapid developments in recent years

• Two types: open and closed cycle

Gas Turbine Cogeneration SystemTher m

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• Open Brayton cycle: atmospheric air at increased pressure to combustor

Open Cycle Gas TurbineTher m

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Air

G

Compressor Turbine

HRSG

CombustorFuel

Generator

Exhaust Gases

Condensate from Process

Steam to Process

• Old/small units: 15:1 New/large units: 30:1

• Exhaust gas at 450-

600 oC

• High pressure steam produced: can drive steam turbine Figure: Open cycle gas turbine cogeneration


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• Working fluid circulates in a closed circuit and does not cause corrosion or erosion

• Any fuel, nuclear or solar energy can be used

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Closed Cycle Gas TurbineHeat Source

G

Compressor Turbine

Generator

Condensate from Process

Steam to Process

Heat Exchanger

Figure: Closed Cycle Gas Turbine Cogeneration System


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• Used as direct mechanical drives

Reciprocating Engine Cogeneration SystemsT

her mal E

quipment/

Cogener ation

Figure: Reciprocating engine cogeneration system (UNESCAP, 2000)

• Many advantages: operation, efficiency, fuel costs

• Used as direct mechanical drives

• Four sources of usable waste heat


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• Supplied fuel first produces power followed by thermal energy

• Thermal energy is a by product used for process heat or other

• Most popular method of cogeneration

Topping CycleTher m

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Bottoming CycleTher m

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• Primary fuel produces high temperature thermal energy

• Rejected heat is used to generate power

• Suitable for manufacturing processes


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Introduction




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Assessment of Cogeneration Assessment of Cogeneration SystemsSystems

• Overall Plant Heat Rate (kCal/kWh):

Ms = Mass Flow Rate of Steam (kg/hr)hs = Enthalpy of Steam (kCal/kg)hw = Enthalpy of Feed Water (kCal/kg)

• Overall Plant Fuel Rate (kg/kWh)

Performance Terms & DefinitionsTher m

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)(

)(

kWOutputPower

hwhsxMs

)(

)/(*

kWOutputPower

hrkgnConsumptioFuel

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• Steam turbine efficiency (%):

Steam Turbine PerformanceTher m

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Gas Turbine Performance• Overall gas turbine efficiency (%) (turbine

compressor):

100)/(

)/(x

kgkCalTurbinetheacrossdropEnthalpyIsentropic

kgkCalTurbinetheacrossDropEnthalpyActual

100)/()/(

860)(x

kgkCalFuelofGCVxhrkgTurbineGasforInputFuel

xkWOutputPower


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• Heat recovery steam generator efficiency (%):

Ms = Steam Generated (kg/hr)

hs = Enthalpy of Steam (kCal/kg)

hw = Enthalpy of Feed Water (kCal/kg)

Mf = Mass flow of Flue Gas (kg/hr)

t-in = Inlet Temperature of Flue Gas (0C)

t-out= Outlet Temperature of Flue Gas (0C)

Maux = Auxiliary Fuel Consumption (kg/hr)

Heat Recovery Steam Generator (HRSG) Performance

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100)]/([)]([

)(x

kgkCalFuelofGCVxMttCpxM

hhxM

auxoutinf

wss


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Ther m

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Introduction




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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities

Steam turbine:

• Keep condenser vacuum at optimum value

• Keep steam temperature and pressure at optimum value

• Avoid part load operation and starting & stopping

Boiler & steam – see other chapters

Steam Turbine Cogeneration System

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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities

Gas Turbine Cogeneration System

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Gas turbine – manage the following parameters:

• Gas temperature and pressure• Part load operation and starting & stopping• Temperature of hot gas and exhaust gas• Mass flow through gas turbine• Air pressure

Air compressors – see compressors chapter

Heat recovery system generator – see waste heat recovery chapter

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Training Session on Energy Training Session on Energy EquipmentEquipment

CogenerationCogeneration

THANK YOU THANK YOU

FOR YOUR ATTENTIONFOR YOUR ATTENTION

© UNEP GERIAP© UNEP GERIAP

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Disclaimer and ReferencesDisclaimer and References

• This PowerPoint training session was prepared as part of the project “Greenhouse Gas Emission Reduction from Industry in Asia and the Pacific” (GERIAP). While reasonable efforts have been made to ensure that the contents of this publication are factually correct and properly referenced, UNEP does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. © UNEP, 2006.

• The GERIAP project was funded by the Swedish International Development Cooperation Agency (Sida)

• Full references are included in the textbook chapter that is available on www.energyefficiencyasia.org

Documents

1 Training Session on Energy Equipment Cogeneration Presentation from the “Energy Efficiency Guide for Industry in Asia”