Thermodynamic and economic analysis of a Kalina cycle-based combined heating and power system for low-temperature heat source utilization

The Kalina cycle is effective for recovering and utilizing low-temperature heat sources, but it suffers from low efficiency. In order to enhance energy conversion efficiency, this paper proposes a novel combined heating and power system that integrates the Kalina cycle with an ammonia-water absorption refrigeration cycle. This system uniquely recovers all wasted heat to generate heating capacity, achieving 100 % thermal efficiency. Detailed thermodynamic and economic models are developed, based on which a performance optimization is conducted and shows that the new system generally outperforms the Kalina cycle with an exergy efficiency of 34.47 % and a payback period of 2.31 years. Further performance analysis reveals that turbine power output significantly impacts economic performance, and most exergy destructions occur in the heat exchanger-type equipment. Finally, a parameter sensitivity analysis explores the effects of seven key variables on system performance. Results indicate that increasing the ammonia concentration of the basic solution and turbine inlet temperature, while decreasing the turbine inlet pressure, improves the exergy efficiency of system. An optimal ammonia concentration of the ammonia-strong solution is identified for achieving the shortest payback period.