Thermodynamic performance study on gas-steam cogeneration systems with different configurations based on condensed waste heat utilization

In view of the limited application of the traditional water-cooled GSPP (gas-steam combined cycle power plant) in water-deficient areas, an air-cooled GSPP is proposed based on AHP (absorption heat pump) to achieve conservation of energy and water in this paper. The thermodynamic performance is compre-hensively compared with three other configurations from both the energy and exergy analysis per-spectives. Four cogeneration systems are considered: traditional water-cooled GDES (GSPP with direct extraction steam for heating), water-cooled GAS (GSPP with AHP system), air-cooled GDES and air-cooled GAS. Compared with water-cooled GDES, net output power, energy and exergy efficiencies increase by 17,815 kW, 1.43% and 1.53% in air-cooled GAS with 384,382 kW heating capacity. The results demonstrate that the performance of an air-cooled GAS can surpass that of a traditional water-cooled GDES, which shows that the energy-saving effect of waste heat recovery can compensate for the performance reduction caused by air cooling modification. Therefore, the traditional water-cooled GDES can be modified into an air-cooled GAS to implement dual purposes of saving energy and water in water-starved regions. The water-cooled GAS achieves the best performance and should be selected in water-rich areas. This research can provide theoretical support for different energy-and water-saving modification needs.