Abstract:

This paper presents a thermodynamic analysis of quasi-nonstationary operation of a power unit with the rated capacity of 370 MW in cogeneration in the system operating in power and frequency regulation of the Polish Power System (PPS). The analysis undertakes the system operation over the period of a year and with different heater configurations. In addition, the analysis, such as reported in is performed for the operation of the power unit with the compensation of its electricity output loss as a result of use of the combined cycle. The relations between the curves of heating steam pressure in the particular extractions of the turbine and IP-LP crossoverpipe were performed in the function of ambient temperatures (demand for heat in households) for the adopted heater configurations.  The resulting curves of pressure and corresponding steam saturation temperatures enable the determination of the temperatures of network hot water at the output of the heaters and calculation of the heat production in them as well as calculation of the use of the chemical energy of fuel in the power unit which is needed for the production of heat. As a consequence, it was possible to calculate and compare energy efficiency of the repowered units for the specific heater configurations.