Energy, exergy, economic and environmental (4E) evaluation of an improved cogeneration system based on compressed air energy storage and absorption heat pump

To simultaneously enhance waste heat recovery, peak shaving and valley filling capacity of existing air-cooled coal-fired cogeneration system, an improved complementary energy supply method is proposed based on absorption heat pump (AHP) and compressed air energy storage (CAES). The improved cogeneration system CPHP-CAES forms a CAES-assisted coal-fired cogeneration mode during charging process and a coal-fired cogeneration assisted CAES mode during discharging process. Energy, exergy, economic and environmental (4E) evaluations are carried out to reveal advantages. Compared with original coal-fired cogeneration system adopting AHP for waste heat recovery (CPHP), maximum output power and heating load of CPHP-CAES are increased by 85.98 MW and 87.39 MW, and minimum output power is decreased by 94.83 MW at an extraction flow rate of 80 kg/s. Meanwhile, the waste heat recovery rates during charging and discharging phases are improved by 4.45 % and 9.41 %, and overall thermal efficiency is enhanced by 1.78 %. The maximum saving coal consumption rate is 3.48 g/kWh. The dynamic payback period (DPP) is reduced by 0.11 years, multiple of invested capital (MOIC) and net present value (NPV) are increased by 0.02 and 81.04 M$. The annual CO2 emissions are reduced by 36,228.53 tons.