Energy Analysis and Optimization of Open Cycle Gas Turbine Power Plant Through Exhaust Heat Recovery

This study investigates the retrofitting of a 25 MW gas turbine (GT) power plant in River State, Nigeria, into a combined cycle gas turbine (CCGT) system for the enhancement of energy efficiency and performance through exhaust heat recovery. Performance data over 37 days was analyzed using SCILAB software, concentrating on maximization of net power output and energy efficiency; and minimization of specific fuel consumption and pollutant emissions. The best performance of the GT power plant indicated a net power output of 21.99 MW, thermal efficiency of 28.89%, and a specific fuel consumption (sfc) of 0.26 kg/kWh on the day 31. In the optimization process, the retrofitted combined cycle gas turbine system showcased a design net power output of 50 MW (25 MW from both gas turbine and steam turbines) and a thermal efficiency of 61.35%. Between 36.63 and 50.53 MWth of waste heat is harnessed during the retrofitting process, thereby contributing to significant minimization of fuel consumption as well as pollutant emissions. This indicates the potential of converting gas turbine power plants into combined cycle gas turbines power plant for improvement in efficiency and sustainability in electricity power generation. This study’s unique contributions include: (i) the integration of supplementary-fired HRSG for a 25MW gas turbine using actual plant data from Rivers state, Nigeria, (ii) the use of SCILAB for comprehensive cycle modeling and optimization, (iii) fuel-specific performance analysis using regional natural gas composition, and (iv) validation of performance enhancement under high ambient temperature conditions relevant to Sub-Saharan Africa. The findings demonstrate that retrofitting OCGT plants with HRSGs and supplementary firing can substantially improve energy efficiency and sustainability in gas turbine-dominated power sectors like Nigeria’s.