co generation

1

Training Session on Energy Training Session on Energy EquipmentEquipment

CogenerationCogeneration

Ther m

al Equipm

ent/C

ogener ation

2

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

3

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

al Equipem

ent/C

ogener ation

4


Efficiency Advantage of CHPTher m

al Equipm

ent/C

ogener ation 100 68

24 Units

34 Units

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)

5


• 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

al Equipm

ent/C

ogener ation

6


Ther m

al Equipm

ent/C

ogener ation

Introduction




7

Type of Cogeneration SystemsType of Cogeneration Systems

• Steam turbine

• Gas turbine

• Reciprocating engine

• Other classifications:

- Topping cycle

- Bottoming cycle

Ther m

al Equipm

ent/C

ogener ation

8


• 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

al Equipm

ent/C

ogener ation

9

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

Back Pressure Steam TurbineTher m

al Equipm

ent/C

ogener ation

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


10

• 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

Ther m

al Equipm

ent/C

ogener ation

Boiler Turbine

Process

HP Steam

LP SteamCondensate

Condenser

Fuel

Figure: Extraction condensing steam turbine


11

• 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

al Equipm

ent/C

ogener ation


12

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

Open Cycle Gas TurbineTher m

al Equipm

ent/C

ogener ation

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


13

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

• Any fuel, nuclear or solar energy can be used

Ther m

al Equipm

ent/C

ogener ation

Closed Cycle Gas TurbineHeat Source

G

Compressor Turbine

Generator

Condensate from Process

Steam to Process

Heat Exchanger

Figure: Closed Cycle Gas Turbine Cogeneration System


14

• 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


15

• 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

al Equipm

ent/C

ogener ation


16

Bottoming CycleTher m

al Equipm

ent/C

ogener ation

• Primary fuel produces high temperature thermal energy

• Rejected heat is used to generate power

• Suitable for manufacturing processes


17


Ther m

al Equipm

ent/C

ogener ation

Introduction




18

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

al Equipm

ent/C

ogener ation

)(

)(

kWOutputPower

hwhsxMs

)(

)/(*

kWOutputPower

hrkgnConsumptioFuel

19

• Steam turbine efficiency (%):

Steam Turbine PerformanceTher m

al Equipm

ent/C

ogener ation

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

compressor):

100)/(

)/(x

kgkCalTurbinetheacrossdropEnthalpyIsentropic

kgkCalTurbinetheacrossDropEnthalpyActual

100)/()/(

860)(x

kgkCalFuelofGCVxhrkgTurbineGasforInputFuel

xkWOutputPower


20

• 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

al Equipm

ent/C

ogener ation

100)]/([)]([

)(x

kgkCalFuelofGCVxMttCpxM

hhxM

auxoutinf

wss


21


Ther m

al Equipm

ent/C

ogener ation

Introduction




22

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

Ther m

al Equipm

ent/C

ogener ation

23

Energy Efficiency OpportunitiesEnergy Efficiency Opportunities

Gas Turbine Cogeneration System

Ther m

al Equipm

ent/C

ogener ation

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

24

Training Session on Energy Training Session on Energy EquipmentEquipment

CogenerationCogeneration

THANK YOU THANK YOU

FOR YOUR ATTENTIONFOR YOUR ATTENTION

Ther m

al Equipm

ent/C

ogener ation

co generation

Documents