Thermodynamic, energy consumption and economic analyses of the novel cogeneration heating system based on condensed waste heat recovery

Highlights: • A novel cogeneration heating system with full waste heat recovery is proposed. • Optimization direction of integration is revealed for waste heat recovery system. • Thermodynamic perfection, energy consumption and economy are analyzed intensively. • Total exergy efficiency of the novel system increases by 6.1–14.1% • Both the heating energy consumption and the unit heating cost are evidently reduced. - Abstract: In order to utilize the condensed waste heat of multi turbine units of cogeneration plant efficiently and simultaneously, a novel cogeneration heating system is proposed. Comparative analyses are made among the conventional cogeneration heating system, the absorption heat pump cogeneration heating system, the high backpressure cogeneration heating system and the novel cogeneration heating system from the aspects of thermodynamics, energy consumption and economy. The research objects are 2 × 300 MW water-cooling turbine units. The aim of the work is to point out the optimization direction of system integration for the novel cogeneration heating system by the thermodynamic analysis, and to reveal the actual heating energy consumption and the unit heating cost of the systems based on the method of equivalent electricity of heating. The study results show that the novel cogeneration heating system reasonably matches the extraction steam, the exhaust steam and the heating network water with each other at different energy levels. Therefore, it has evident advantages in the aspects of the thermodynamic perfection, the actual heating energy consumption and the economy. Compared with other systems, the novel cogeneration heating system increases the total exergy efficiency by 6.1–14.1%, reduces the equivalent electricity of heating by 11.1–29.4% and reduces the unit heating cost by 8.7–23.9%.