Environmental Engineering Reference
In-Depth Information
Reciprocating
engine
Micro-turbine
Stirling engine
Fuel cell
Fuel/
heat source
Fuel
Fuel
Fuel
Combustion
in piston
Combustion
in turbine
Combustion
in burner
Re-formation
Electro-chemical
conversion
Stirling process
Mechanical
energy
Mechanical
energy
Mechanical
energy
Electricity
Electricity
Electricity
Electricity
Heat
Heat
Heat
Heat
Combustion process
Electro-chemical
process
Figure 4.7
Summary of procedures to obtain electricity and heat for CHP
technologies [76]
or in developing stages. From all of these technologies, today the reciprocating type
is the most proven, especially within industrial sites due to its high reliability and fuel
flexibility. Still, advances in technology and economies of scale have lead to a high
interest in micro-generators with the objective of providing electrical and thermal
power for a new set of customers. Hence, micro-CHP devices are becoming suitable
for residential and commercial applications, usually having an electric capacity well
below 100 kW
el
and as low as 1 kW
el
[59].
Although Stirling engines offer lower electrical efficiencies than reciprocating
engines, they are generally considered to be more appropriate for domestic applica-
tions as they are quieter and have the potential for a longer operating life. In general,
due to their proven performance, reciprocating and Stirling engine technologies are
the most popular and easily available in the market. Meanwhile, micro-turbines are
yet to be successfully implemented on a small-scale and fuel cell-based micro-CHP
systems are thought to be a few years away from being marketable. Within this con-
text, this topic mainly focuses on cogeneration technologies for use in dwellings
and small businesses; thus, they distinguish themselves from systems supplying heat
to a district or urban area. As a consequence, the terms CHP and micro-CHP are
interchangeable in this text.
It is important to comprehend the relationship between electrical and thermal
power in a dwelling and the role micro-CHP can play. Therefore, simple illustra-
tions are given in Figures 4.8 and 4.9 depicting the provision of electricity and hot
water through conventional methods and under the presence of a micro-CHP system
respectively.
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