Effects of structural and ample composition and process activities of a substation at district heating systems on energy efficiency

The district heating system should be accepted as a technical system, functionally and workable to provide heat for thermo technical needs of a higher number of different and connected us ers being located on a wider area usually in urban environment. The thermo technical needs of users mean the needs for heating, ventilation, air conditioning, and preparation of consume sanitary hot water and/or for special purposes. The district heating system on defined quality level provides heating and its delivery to users. The district heating systems are complex in their contents, conditioned in structure and non-alternative in processes and they may be active during heating season or during the entire calendar year.
The DHS is projected on the bases of established and emphasized requirements in written project task, on the level of consciences and expertise of engaged designers, of material, equipment and components being present on open market; after that it is realized by contractors having references and routines and after tests, regulations, technical checks and acceptances they are given to an investor for use in accordance with culture of users. The district heating system is projected and dimensioned for needs of defined environment but also for a longer period of its development; therefore it is constantly developed, reconstructed, revitalized and maintained up to limits of technical, ecological and economic justification in lifetime.
General model of structural arrangement of the DHS, on the level of a subsystem is timely defined [8].The structure is composed of seven constitutive subsystems from No 1 to No 7, where No 4 subsystem is recognized between them, being defined for direct exchange of heat in the sense of delivery of heat to users connected actively to the DHS. Practically, the No 4 subsystem integrates all substations in the one DHS and regularly with not a low number; for example in the town of Pozarevac there are cca 300 active substations in one DHS, and in the city of Kragujevac there are cca 1500 active substations in three DHS. Indisputably there are no DHS without the No 4 subsystem but the No 4 subsystem considerably effects representative quality of the DHS as a whole [10].