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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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© UNEP 2006© UNEP 2006
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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© UNEP 2006© UNEP 2006
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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© UNEP 2006© UNEP 2006
IntroductionIntroduction
Efficiency Advantage of CHPTher m
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ogener ation 100 68
24
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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© UNEP 2006© UNEP 2006
IntroductionIntroduction
• 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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© UNEP 2006© UNEP 2006
Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
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Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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© UNEP 2006© UNEP 2006
Type of Cogeneration SystemsType of Cogeneration Systems
• Steam turbine
• Gas turbine
• Reciprocating engine
• Other classifications:
- Topping cycle
- Bottoming cycle
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© UNEP 2006© UNEP 2006
Type of Cogeneration SystemsType of Cogeneration Systems
• 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
Type of Cogeneration SystemsType of Cogeneration Systems
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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
Type of Cogeneration SystemsType of Cogeneration Systems
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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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Type of Cogeneration SystemsType of Cogeneration Systems
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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
Type of Cogeneration SystemsType of Cogeneration Systems
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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
Type of Cogeneration SystemsType of Cogeneration Systems
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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
Type of Cogeneration SystemsType of Cogeneration Systems
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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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Type of Cogeneration SystemsType of Cogeneration Systems
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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
Type of Cogeneration SystemsType of Cogeneration Systems
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© UNEP 2006© UNEP 2006
Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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© UNEP 2006© UNEP 2006
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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© UNEP 2006© UNEP 2006
• 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
Assessment of Cogeneration Assessment of Cogeneration SystemsSystems
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© UNEP 2006© UNEP 2006
• 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
Ther m
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100)]/([)]([
)(x
kgkCalFuelofGCVxMttCpxM
hhxM
auxoutinf
wss
Assessment of Cogeneration Assessment of Cogeneration SystemsSystems
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© UNEP 2006© UNEP 2006
Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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© UNEP 2006© UNEP 2006
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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© UNEP 2006© UNEP 2006
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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Ther m
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© UNEP 2006© UNEP 2006
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
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