Exergy, economic, and climate performance evaluation of an efficient clean cogeneration system driven by low-temperature waste-heat

Abstract

Currently, waste-heat emissions from industrial processes contribute significantly to climate change. Effective recovery of waste-heat is crucial for saving energy and mitigating global warming. In this study, we proposed a clean, low energy consuming cooling and power generation system driven by waste-heat at 130 °C, and compared it to the existing system. For comparing the two systems, R1234yf was used as the refrigerant, which was the best-performing refrigerant among the seven HFOs evaluated. The performance, economic efficiency, and environmental impact of the two systems were comprehensively compared based on exergy, economic, and climate performance assessments. The results showed that exergy efficiency of the proposed system was 85.46%, which was 10.08% higher than that of the original system. The equipment investment cost by the proposed system decreased by 21.17% (from $3.36 × 105 to $2.65 × 105), as compared to the original system. Moreover, the annual operating and total costs were reduced by 24.59% and 21.28%, respectively, compared to the original system. In terms of climate performance assessment, the proposed system reduced emissions by 1.18 × 107 kg CO2eq. Additionally, the proposed system reduced 1.33 × 107 kg CO2eq compared to the original system that produced 1.50 × 106 kg CO2eq. Taken together, the proposed system achieved higher exergy efficiency while reducing costs and environmental impact. This was due to the heat integration technology used to achieve energy cascading, low-energy ejectors instead of energy-intensive compressors, and the use of environmentally friendly HFO as refrigerant. In future, the proposed system could provide a reference for efficient recovery of low-temperature industrial waste-heat and development of energy systems adapted to current trends in clean industrial production.