COMBINED HEAT AND POWER (CHP)
--- P. S. KULKARNI
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Combined Heat and Power (CHP) systems can provide a range of benefits to
users with regards to efficiency, reliability, costs and environmental impact.
What is a small generation unit, e.g. a wind farm or a CHP system, connected
to the transmission network?
Theoretically, the two following situations can occur:
1. a CHP system is located on a large industrial site and the industrial customer
is directly connected to the transmission network. In this case, the CHP
system can be described as distributed generation as it is connected on the
customer side of the meter;
2. a medium-sized wind farm is directly connected to the transmission system,
due to the capacity limit of the local distribution network. In this case, the
wind farm cannot be described as distributed generation.
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Combined Heat and Power (CHP). Only the power generation technologies that
produce excess heat can be used for CHP applications; these include engines,
combustion turbines, fuel cells, and microturbines. Additional equipment must
be installed to capture the heat and use it in the secondary process, at an
average additional cost of $400/kW. Engines and turbines (including some
microturbines) have been used for CHP applications.
Any DER technology that can produce waste heat can be used in a CHP
application with greater overall system efficiencies (because of the higher fuel
utilization efficiency) and perhaps better economics.
DGs providing CHP as a cogeneration has a high overall energy utilization
efficiency. The produced heat, from converting fuel into electric power process,
is used onsite for a wide range of applications in hospitals, large commercial
areas and process industries.
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Combined Heat and Power - Many types of distributed generation can provide useful
and valuable thermal energy by capturing excess heat energy produced during
electricity generation and using it to heat or cool water or interior space. The excess
heat can also be used as energy input to an industrial process, in lieu of burning fuel.
This energy capture and reuse process is known as combined heat and power, CHP,
or cogeneration. Some energy users require substantial amounts of heat, especially
for industrial, institutional and agricultural operations. In those cases, CHP can save
enough on fuel costs to substantially improve the overall economics of DER
installations.
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COGENERATION
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It means sequential conversion of
energy contained in fuel into two or
more usable forms. The two forms can
be STEAM and ELECTRICITY.
COGENERATION SYSTEM –
Inplant Power Generation System
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Inplant Power Generation System
If cogeneration is used, the boiler is made to produce steam at higher temp.
and pressure than needed for manufacturing purposes. This steam is used in
Turbine – Gen. set to produce electricity. The exhaust steam (from turbine) is
used for manufacturing purpose.
The reject heat utilization system is used in power plants. Some steam is extracted
From the turbine (at a suitable temp. and pressure) and supplied to an adjacent
industry for manufacturing purposes. This is shown in Fig.2.
The Inplant Power Generation System can be Topping Cycle or Bottoming cycle.
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Inplant Power Generation System Modes TOPPING CYCLE:
Fuel is burnt in the boiler to produce high pressure steam. This steam
is expanded in a turbine coupled to a Gen. to give electric Power.
The reject heat from the turbine is used for manufacturing
process.
BOTTOMING CYCLE:
Fuel is burnt in the boiler to produce steam. This steam is used for
manufacturing process. The reject heat from process is used to
generate electrical Power. It has limited utility.
BENEFITS OF COGENERATION:
1. FUEL ECONOMY
2. LOWER CAPITAL COSTS / kW OF INSTALLED CAPACITY IN
POWER PLANTS.
3. LOWER GESTATION PERIOD.
4. SAVING TO INDUSTRY FROM POWER CUTS AND POWER
SUPPLY INTERRUPTION.
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EX:
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Home Work:
Q.1. Visit the various websites and study the case studies using CHP / Cogeneration.
Ex. : https://www.thermaxglobal.com/case_studies/
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