cogeneration

1. presented BY :-
Pratik gupta (eee 6TH SEM )

2. CONTENTS:-
 Introduction
 Types of cogeneration systems
 Benefit of cogeneration
 Energy efficiency

3. Introduction:-
 Cogeneration is also called CHP system.
 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

4. Type of Cogeneration Systems:-
• Steam turbine
• Gas turbine
• Reciprocating engine
• Other classifications:
 - Topping cycle
 - Bottoming cycle

5. Steam Turbine Cogeneration System:-
• 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

6. • Steam exits the turbine at a higher pressure than the
atmospheric
Back Pressure Steam Turbine
Fuel
Figure: Back pressure steam turbine
Advantages:
-Simple configuration
-Low capital cost
-Low need of cooling
water
-High total efficiency
Disadvantages:
-Larger steam turbine
Boiler Turbine
Process
HP Steam
Condensate LP
Steam

7. • Steam obtained by
extraction from an
intermediate stage
• Remaining steam is
exhausted
• Relatively high
capital cost, lower
total efficiency
Extraction Condensing Steam
Turbine
Boiler Turbine
Process
HP Steam
LP Steam
Condensate
Condenser
Fuel
Figure: Extraction condensing steam turbine

8. • 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 System

9. • Open Brayton cycle:
atmospheric air at
increased pressure to
combustor
Open Cycle Gas Turbine
Air
G
Compressor Turbine
HRSG
Combustor
Fuel
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

10. • Working fluid circulates
in a closed circuit and
does not cause
corrosion or erosion
• Any fuel, nuclear or
solar energy can be
used
Closed Cycle Gas Turbine
Heat Source
G
Compressor Turbine
Generator
Condensate
from Process
Steam to
Process
Heat Exchanger
Figure: Closed Cycle Gas Turbine Cogeneration System

11. 11
• Used as direct mechanical drives
Reciprocating Engine Cogeneration
Systems
Figure: Reciprocating engine cogeneration system
• Many advantages:
operation, efficien
cy, fuel costs
• Used as direct
mechanical drives
• Four sources of
usable waste heat

12. 12
© UNEP 2006
• 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 Cycle

13. Bottoming Cycle
• Primary fuel produces high
temperature thermal energy
• Rejected heat is used to generate
power
• Suitable for manufacturing processes

14. • 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)

15. Energy 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
Steam Turbine Cogeneration System

16. Energy Efficiency Opportunities
Gas Turbine Cogeneration System
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