Combine Heat Power Plants detail Presentation

1. Combined Heat and Power Plant (CHP)
Lecture 6

2. Combined Heat and Power
 Combined heat-and-power, also known as “cogeneration,” refers to the
use of recovered exhaust heat of any production unit for another
process requirement.
 This in turn results in improvement in the energy utilization of the unit.
By so doing, the overall thermal efficiency of generation may be raised
from 40–50% to 70–90%. The upper limit of 90% holds for large
installations with a very well-defined and constant heat demand.

3.  Combined heat-and-power does not have to be a renewable source
of energy; in fact, many CHP installations use natural gas as a
source.
 The use of biomass as a source is the only renewable form of CHP.
The direct combustion of organic matter to produce steam or
electricity is the most advanced of the different CHP processes and,
when carried out under controlled conditions, is probably the most
efficient.

4.  Large CHP installations are used for production of steam in industrial
installations, for space heating in the agriculture, and for district heating.
Agricultural CHP is very common in the Netherlands and in Denmark,
where about 25% of electricity comes from CHP. Recently, incentives
toward smaller generation units have resulted in a growth in CHP in some
countries.
 Micro CHP plants used for space heating and electricity receiving a lot of
attention. Possible applications are domestic heating, hotels shopping
centers and offices.
 For example, a somewhat larger unit produces 105kW electricity and
172kW heat. A market for much smaller units may be emerging, intended
for heating of domestic premises.
 An example is a unit that produces 1 kW electricity together with 7.5–
12kW heat.

5. Categories of CHP applications
Four categories of CHP applications:
 small-scale CHP schemes: to meet space and water heating requirements in
buildings, based on spark ignition reciprocating engines
 large-scale CHP schemes: for steam raising in industrial and large buildings,
based on
compression ignition reciprocating engines, steam turbines or gas turbines
 large scale CHP schemes for district heating: based around a power station or
waste
incinerator with heat recovery supplying a local heating network
 CHP schemes fuelled by RES: these may be at any scale

19. Combined Cycle Schematic

20. Energy
Distribution
in a combined
cycle system

22. Two pressure
level system

24. Features
Very mature technology
 Size: 0.5 – 30+ MW
 Efficiency: electricity (20 – 45%), cogeneration (80 – 90%)
 Installed cost ($/kW): 400 – 1,200
 O&M cost ($/kWh): 0.003 – 0.008
 Fuel: natural gas, biogas, propane
 Emission: approximately 150 – 300 ppm NOx (uncontrolled)
below approximately 6 ppm NOx (controlled)
 Cogeneration: yes (steam)
 Commercial Status: widely available
 Three main components: compressor, combustor, turbine
 Start-up time range: 2 – 5 minutes
 Natural gas pressure range: 160 – 610 psig
 Nominal operating temperature: 59 F
Combustion Gas Turbines24

25. Combustion Gas Turbines
Combustor
Power
Converter
Compressor
air
fuel
Power Turbine
Generator
HRSG
(Heat Recovery
Steam Generator)Feed water
Process steam
Fig. 1 Block diagram of Combustion Gas Turbine System.
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26. CHP Technologies

27.  Advantages
 High efficiency and low cost (particularly in large systems)
 Readily available over a wide range of power output
 Marketing and customer serving channels are well established
 High power-to-weight ratio
 Proven reliability and availability
 Disadvantages
 Reduced efficiencies at part load
 Sensitivity to ambient conditions (temperature, altitude)
 Small system cost and efficiency not as good as larger systems
 Advantages & Disadvantages
Combustion Gas Turbines
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28. Comparison CHP

29. Micro-turbines29

30.  Size: 25 – 500 kW
 Efficiency: unrecuperated (15%), recuperated (20 – 30%), with heat recovery (up to 85%)
 Installed cost ($/kW): 1,200 – 1,700
 O&M cost ($/kWh): 0.005 – 0.016
 Fuel: natural gas, hydrogen, biogas, propane, diesel
 Emission: below approximately 9 - 50 ppm NOx
 Cogeneration: yes (50 – 80C water)
 Commercial Status: small volume production, commercial prototypes now
 Rotating speed: 90,000 – 120,000
 Maintenance interval: 5,000 – 8,000 hrs
Micro-turbines
 Features
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31.  Advantages
 Small number of moving parts
 Compact size
 Light-weight
 Good efficiencies in cogeneration
 Low emissions
 Can utilize waste fuels
 Long maintenance intervals
 Disadvantages
 Low fuel to electricity efficiencies
Micro-turbines
 Advantages & Disadvantages
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32. Overview of CHP Technologies
Technology Pros Cons
Fuel Cell - Very low emission
- Exempt from air and permitting in
some areas
- Comes in a complete “ready to
connect” package
- High initial investment
- Limited number of
commercially available units
Gas Turbine - Excellent service contracts
- Steam generation capabilities
- Mature technology
- Requires air permit
- The size and shape of
generator package is
relatively large
Micro-turbine - Lower initial investment
- High redundancy
- Low maintenance cost
- Relative small size and installation
flexibility
- Relatively new technology
- Requires air permit
- Synchronization problems
possible for large
installations
Recip.
Engine
- Low initial investment
- Mature technology
- Relatively small size
- High maintenance costs
- Low redundancy

33. Benefits of CHP
High Efficiency, On-Site Generation Means
 Improved Reliability
 Lower Energy Costs
 Lower Emissions (including CO2)
 Conserve Natural Resources
 Support Grid Infrastructure
 Fewer T&D Constraints
 Defer Costly Grid Upgrades
 Price Stability
 Facilitates Deployment of New Clean Energy
Technologies
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34. Factors for CHP Suitability
 High Thermal Loads-(Cooling, Heating)
 Cost of buying electric power from the grid versus to
cost of natural gas (Spark Spread)
 Long operating hours (> 3000 hr/yr)
 Need for high power quality and reliability
 Large size building/facility
 Access to Fuels (Natural Gas or Byproducts)
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35. Generators
Two Types of Generators
Induction
• Requires Grid Power
Source to Operate
• When Grid Goes
Down, CHP System
Goes Down
• Less Complicated &
Less Costly to
Interconnect
• Preferred by Utilities
Synchronous
• Self Excited (Does Not
Need Grid to Operate)
• CHP System can
Continue to Operate
thru Grid Outages
• More Complicated &
Costly to Interconnect
(Safety)
• Preferred by Customers
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36. Environmental Benefits of CHP (NOx)36

37. 186
lb/MMBtu
Power Station Fuel
(U.S. Fossil Mix)
117
CHP Fuel
(Gas)
Lb/MMBtu
CO2 Emissions Reductions from CHP
39,000 Tons CO2 Saved/Year
Power Plant
6.0
MWe
70,000
pphSteamBoiler117
Boiler Fuel (
Gas)
Lb/MMBtu
CO2 Emissions
56k Tons/yr
CO2 Emissions
43k Tons/yr
…TOTAL ANNUAL CO2 EMISSIONS…95k Tons 56k Tons
CO2 Emissions
52k Tons/yr
Conventional Generation Combined Heat & Power:
Taurus 65 Gas TurbineEfficiency: 31%
Steam
Efficiency: 80%
Efficiency: 82.5
%

38. CHP and Energy Assurance
Combined Heat & Power (CHP) can Keep Critical Facilities Up
& Operating During Outages
For Example, CHP can Restore Power and Avoid:
– Loss of lights & critical air handling
– Failure of water supply
– Closure of healthcare facilities
– Closure of key businesses
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