Renovating a gas turbine power plant to a cogeneration system for district heating in Algeria: Performance evaluation of the upgraded CHP

This study presents an integrated assessment of waste heat recovery from an existing Algerian gas turbine (GT) power plant retrofitted as a Combined Heat and Power (CHP) system for District Heating (DH) applications. Unlike conventional studies that assess thermodynamic performance and heat demand separately, this work proposes an integrated framework that combines process simulation, demand estimation, and sustainability evaluation. The system is modeled using Aspen HYSYS, while the DH demand of the Aïn Beïda urban area is estimated using the degree-day method. The results demonstrate that upgrading the F’Kirina power plant to CHP mode significantly enhances overall efficiency from 33.6% to 88.1%. The integrated analysis indicates that, from an annual energy-balance perspective, the recovered waste heat is theoretically sufficient to satisfy the estimated heating demand of Aïn Beïda. Practical implementation will require dedicated studies on District Heating Network (DHN) design, thermal storage, and peak-load management. Sensitivity analysis reveals that electricity generation is strongly affected by ambient temperature, whereas heat recovery remains comparatively stable. Exergy analysis identifies the combustion chamber and Waste Heat Recovery Exchanger (WHRE) as the dominant sources of irreversibility. Furthermore, a sustainability assessment based on the Sustainability Index (SI) shows a marked improvement in exergetic performance, with SI rising from 1.46 to 1.80 after CHP integration. Environmentally, the CHP configuration reduces specific fuel consumption from 243.2 to 189.8 kg/MWh and CO ₂ emissions per MWh by 29% (from 616.8 to 437 kg CO ₂ /MWh). Annual avoided emissions through the substitution of conventional heating amount to 58.6 kt CO ₂ /year. The proposed framework provides a comprehensive tool for evaluating CHP retrofitting strategies by linking energy production, demand profiles, and thermodynamic efficiency. These findings underscore the theoretical feasibility of CHP-based DH as a pathway to improve energy efficiency, reduce environmental impacts, and provide benchmarks to support future large-scale feasibility and infrastructure planning studies.