Assessment of Thermal Power Generation Efficiency and Losses in the Sapele Power Station, Delta State

Thermal power generation efficiency in Nigerian gas-fired stations has significant implications for the national electricity grid's capacity, gas consumption, and carbon footprint, yet comprehensive efficiency assessments of individual stations remain largely absent from the engineering literature. This study assesses thermal efficiency performance and energy loss distribution in the Sapele Power Station, Delta State, using operational data and the ASME power test code methodology for steam turbine and gas turbine plant. Monthly generation data, fuel consumption records, cooling water flow measurements, and flue gas temperature readings were obtained from the plant's control room and engineering records covering a 24-month period. Heat rate computations, Sankey energy flow diagrams, and exergy analysis were conducted to quantify and allocate losses across the major system boundaries including the combustion chamber, heat recovery steam generator, steam turbine, condenser, and auxiliary systems. Findings indicated a mean plant heat rate of 14,200 kilojoules per kilowatt-hour, corresponding to a first-law efficiency of approximately 25.4 percent, significantly below the design efficiency of 35 percent. Condenser and flue gas losses collectively accounted for 58 percent of total energy losses. Turbine degradation and boiler scale formation contributed to additional avoidable losses estimated at 4.8 percentage points of efficiency. The study recommends targeted refurbishment of the condenser cooling circuit, turbine blade inspection, and boiler water treatment programme. Keywords: thermal efficiency, power station, heat rate, energy losses, Sapele.