Combined Micro-Systems - Design for Micro-Combined Cooling, Heating and Power Systems - page 60

Fig. 1 CHP technologies requirements [ 1 ]

represent the basic components and, to a certain extent, determine the architecture of
these systems.
The performance characteristics of a CHP system are overall ef ciency, electric

ef ciency is

dependent on many factors, such as technology used, fuel types, operation point,
size of the unit, and also on the heat potential. All these characteristics are closely
linked to the primary engine of the CHP system. That is why cogeneration tech-
nologies for residential, commercial, and institutional applications can be classi

ciency, power, power-to-heat ratio, and start-up time. The overall ef

ed
according to their prime mover and to where their energy source is derived from.
Present day technologies of cogeneration in mCHP systems [ 2 ] are based on the
recuperation of the thermal energy of the following prime movers:

Steam turbines, which are capable of operating over a broad range of steam
pressures. They are custom designed to deliver the thermal requirements of CHP
applications through use of backpressure or extraction steam at the appropriately
needed pressure and temperature.

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Gas turbines, which produce a high quality (high temperature) thermal output.

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Reciprocating engines, which are well suited for applications that require hot
water or low-pressure steam.

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Stirling engines.

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Fuel cells, where the waste heat can be used primarily for domestic hot water
and space heating applications.

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1.1 Steam Turbines

Steam turbines represent the widest used technology in industrial electric plants [ 3 ].
The thermodynamic cycle which lies at the basis of conventional steam plant
functioning may be the one with overheated steam (the Hirn cycle) or the one with