The proton exchange membrane(PEM) electrolyzer can convert green electricity into hydrogen energy

but the conversion efficiency of PEM electrolyzer is low

the thermal energy in the electrolyzer outlet water is not fully utilized. To fully use the waste heat in the PEM electrolyzer hydrogen production system

integrated systems incorporating a 660 MW coal-fired unit and PEM electrolyzer are proposed in both power generation(PG) and combined heat and power(CHP) scenarios. EBSILON and MATLAB Simulink softwares are applied for modelling

and thermodynamic and economic analysis is conducted. In PG scenario

the electrolyzer outlet water is used to heat the feedwater of coal-fired unit. While for CHP scenario

the electrolyzer outlet water is used to heat the return water from heating supply network along with the extraction steam. The produced oxygen is sent into the boiler for combustion. The results show that

compared with the reference coal-fired unit

in PG scenario

the power output is enhanced by 2.55 MW with an power supply efficiency rise of 0.17%

and the boiler efficiency increases by 0.04%. While in CHP scenario

the power output can be enhanced by 5.83 MW with an efficiency rise of 0.40%. After attributing the net power output increment to the PEM hydrogen production system

the exergy efficiency of the PEM hydrogen production system is 69.74% in PG mode with an increase of 3.44%

and 75.41% in CHP mode with an increase of 9.11%. For these two scenarios

the system exergy efficiencies reach up to 40.20% and 40.18%. Economic analysis shows that

the annual income growth by selling electricity for PG and CHP scenarios are 5 460 000 yuan and 12 460 000 yuan

with the increments of net present value of 61 320 000 yuan and 140 140 000 yuan

respectively. The levelized cost of hydrogen production in the reference system is 42.72 yuan/kg. The levelized cost of hydrogen production in PG and CHP modes in the integrated system is 42.55 yuan/kg and 40.79 yuan/kg

respectively.