Techno-economic evaluation on a new integration of air-cooled coal-fired power plant and dual-pressure organic Rankine cycle for cold-side waste heat recovery

To boost coal-fired plants energy efficiency for load-regulation demands. an integration scheme (CPG-DPORC) is proposed wherein multiple extraction steams of different grades from the air-cooled coal-fired power generation system (CPG) drive the dual-pressure organic Rankine cycle (DPORC) step-by-step in a relay way. This scheme combines the high thermo-power conversion of the organic Rankine cycle for low- and medium-grade heat sources and the steam Rankine cycle for high-grade ones. It also flexibly matches CPG and DPORC heat sources, enabling deeper steam energy segmentation. Through such modifications, this approach achieves multiple goals: enhancing power output, recovering exhaust heat, and preventing air-cooling system freezing. A techno-economic evaluation of a 600 MW CPG system showed the retrofit significantly increased output power. Notably, the CPG-DPORC system shows directionally opposite performance advantages over the integrated simple organic Rankine cycle system (CPG-SORC). When the heat distribution ratio reaches 1 at 100 % THA, compared to the original CPG system and CPG-SORC system, the CPG-DPORC system, improves energy efficiency by 0.89 % and 0.17 %, improves exergy efficiency by 0.87 % and 0.17 %, and reduces the standard coal consumption rate by 6.59g/kWh and 1.23g/kWh. Economic evaluations further demonstrate that the initial total investment cost increases by 13.34 × 106USD and 0.57 × 106USD, the levelized cost of electricity (LCOE) reduces by 0.90 USD/MWh and 0.24 USD/MWh and the dynamic payback period (DPP) is shortened by 0.36 years and 0.10 years. Environmental evaluations show that the CO2 emission decrement increases by 66,841.84 tons/year and 12,739.54 tons/year. This integration promotes the shift to a renewable-dominated energy structure.