Civil Engineering Reference
In-Depth Information
7.6
End Users and Load Management
Figure
7.9
shows a basic scheme for an electric system together with average
efficiency values for different end users.
Note that the efficiency of the abovementioned electric end users is generally
high, particularly in electrical drives, and no significant improvement can be made
in the efficiency of the single component. Nevertheless, high-efficiency motors,
where efficiency is 2-3 % points higher than in normal-efficiency motors, can be
justified both technically and economically when the working hours are more than
4,000-5,000 h/year. Better results can be obtained by improving the performance of
general guidelines to determine priorities in an energy-saving program.
In addition, actions such as the application of load-management techniques may
give economic benefits on utility rates. This result is achieved by reducing power
peaks without sacrificing production quality or quantity and by shifting energy
consumption from peak hours to low-rate hours. A proper choice of the loads to be
controlled and of the shutdown sequence can lead to noticeable cost saving and also
to effective energy saving by reducing energy waste, particularly in facility plants.
Microcomputer or computerized energy management control systems are widely
used in factories and in large buildings. They generally prove economical,
depending on the complexity of the installation (number of loads, layout of the
plant, power of the single controlled load); they are becoming more and more
attractive for use in conjunction with non-energy functions such as monitoring and
controlling pollution-producing equipment, managing preventive maintenance,
recording production, and other non-engineering functions.
Fig. 7.9
Typical values of overall efficiency from site boundaries to electric equipment terminals
