Energy and exergy analysis of a new cogeneration system based on an organic Rankine cycle and absorption heat pump in the coal-fired power plant.

• Proposed a new method to simultaneously improve power and heating capacity. • Established mathematical models based on energy and exergy method. • Performance improvement is quantitatively revealed. • Both thermal efficiency and exergy efficiencies are significantly improved. A new cogeneration system based on ORC (organic Rankine cycle) and AHP (absorption heat pump) is presented to achieve the dual effects of improving power output and heating capacity in a coal-fired power plant. The heat source for heating is firstly led into the ORC to generate power, and then is led into the AHP as the driving heat source to recycle waste heat from exhausted steam of the ST (steam turbine) when the energy grade is reduced to a level that matches with the heating energy grade. On the basis of the thermodynamic first and second law, focusing on 135 MW coal-fired power plant, the energy and exergy analyses of traditional cogeneration system and new cogeneration system with ORC and AHP have been completed. Compared to the traditional cogeneration system, the power output and heating capacity are respectively increased by 1.47 MW and 32,106.64 kW when the flow rate of heating extraction steam is 40 kg/s. The integral thermal and exergy efficiencies are improved by 9.38% and 1.71%. Moreover, the coal consumption decrement for power generation and heat-supplying both augments with increasing heating extraction flow rate and decreasing load. The new presented scheme can not only reduce the irreversible loss of the cogeneration system but also save coal consumption. [ABSTRACT FROM AUTHOR]