part 1: overview of cogeneration and its status in asia - Fire

4 Part I: Overview of cogeneration and its status in Asia
1.2 Principle of Cogeneration
Cogeneration is defined as the sequential generation of two different forms of useful energy
from a single primary energy source, typically mechanical energy and thermal energy.
Mechanical energy may be used either to drive an alternator for producing electricity, or
rotating equipment such as motor, compressor, pump or fan for delivering various services.
Thermal energy can be used either for direct process applications or for indirectly producing
steam, hot water, hot air for dryer or chilled water for process cooling.
Cogeneration provides a wide range of technologies for application in various domains of
economic activities. The overall efficiency of energy use in CHP mode can be up to 80 per
cent and above in some cases. A typical small gas turbine based CHP unit can save about
40 per cent of the primary energy when compared with a fossil fuel fired conventional power
plant and a boiler house (see Figure 1.1 below). Along with the saving of fossil fuels,
cogeneration also allows to reduce the emission of greenhouse gases (particularly CO2
emission) per unit of useful energy output. The production of electricity being on-site, the
burden on the utility network is reduced and the transmission line losses eliminated.
Input
Energy
100
Heat Loss
20
Electricity
30
Heat
50
Heat Loss
6
Heat Loss
56
Input for
Power
Generation
(i) Cogeneration System (ii)Conventional System
86
Input for
Boiler
Figure 1.1 Conventional energy system versus cogeneration system
56
Input
Energy
Cogeneration makes sense from both macro and micro perspectives. At the macro level, it
allows a part of the financial burden of the national power utility to be shared by the private
sector; in addition, indigenous energy sources are preserved or the fuel import bill is reduced.
At the micro level, the overall energy bill of the users can be reduced, particularly when there
is a simultaneous need for both power and heat at the site, and a rational energy tariff is
practised in the country.
1.3 From Self Electricity Generation to Cogeneration
In Asian developing countries, it is not unusual to come across situations of grid power
supply interruptions either due to technical failure of the system or because the consumer
demand during a given time period exceeds the utility supply capacity. Industries and
commercial buildings normally adopt stand-by power generators for taking care of their
essential loads during these periods. It is essential to assure continuity of some activities to
minimize production losses or guarantee minimum comfort of the clients. The stand-by
generators have limited use in the year; moreover, these devices require investment and
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