Hydraulic analysis for a district heating system supplied from two CHP plants

High-power heating systems are supplied with heat mainly from CHP plants of various heat and electricity generation capacities. Cogeneration systems have an advantage over separate systems due to their greater economic efficiency and consequently, lesser impact on the environment. However, cogeneration systems do not always operate in optimal operating schemes; often the share of peak power of water boilers in the total source power is excessive. Heating networks powered from two, three or more directions create local ring structures, which in the system operate in separate schemes allocated to areas supplied from one source. Each source supplies heat only for one fragment of the heating system and very often the sources operate with powers different from their optimum conditions. In the end, the sources should operate to create a common network with flexible switching of supply from each source. Operating the heating system in an open scheme will let each source run at optimum efficiency, thereby delivering considerable economic and ecological advantages by increasing the cogeneration coefficient, and also enhancing heat supply safety for recipients. At present [1], Polish heating systems produce 414 PJ of heat, of which as much as 224 PJ is cogenerated heat, accounting for 54% of the total heat produced in heating systems. Working towards a common open network makes it possible to achieve a slight increase in the efficiency of operating cogeneration sources, though in the case of large-scale heat and electricity production it causes a worthy reduction in the emission of CO2 and other pollutants to the atmosphere.

► A common open heating system creates the possibility of changes in heat supply area.
► Two CHP plants in an open heating network increase the safety of the heating system.
► An open scheme of heating system will let each source run at optimum efficiency.