Performance comparison of cylindrical and diverging solar chimney power plants

• Divergent Solar Chimney Power Plants (SCPPs) can achieve a 237% power gain over conventional cylindrical chimneys, cutting construction costs by up to 70%. • Divergent SCPPs achieve efficiencies of about 4.63 times higher than cylindrical designs, with optimal divergence angles between 2° and 5°. • Small-scale SCPPs of both types was tested at Addis Ababa University and it confirmed a 346% power gain. • Systematic optimization on the palnt's geometry (size and configuration), airflow, and thermal management needs to be numerically analyzed to enhance performance. Solar Chimney Power Plants (SCPPs) are promising renewable energy technology that utilize solar energy to generate electricity. The conventional cylindrical SCPP, as exemplified by the Manzanares prototype, produced 50 kW of power with a 194.6 m chimney and a 244 m collector. However, divergent SCPPs demonstrated higher efficiency. The purpose of this study is to analyze and compare the key performance parameters of these two plants by examining the current experimental and simulation findings. Prior reviews have also not gone much into the impact of chimney's divergence angle or area ratio (AR) on the airflow dynamics. With an optimal area ratio (AR) of 4.1, they achieved a power output of 168.5 kW showing an increment of about 237% over cylindrical designs. Other studies showed that increasing chimney height of a small sized divergent SCPP from 4 m to 8 m could lead to improve the temperature change by 513.3% (from 1.5°C to 9.2°C) that caused the power output to increase by 252%. Numerical simulations indicated that a 38.9 m divergent chimney can match the power output of a 194.6 m cylindrical chimney and reduce construction costs by 70%. Additionally, Bell-mouth integration could further enhance the airflow by 6-7% and boosts turbine power by 21%. In general, this review highlights the critical role of geometric optimization for maximizing plant's efficiency. Unlike previous reviews, this study gives more of quantitative analysis. Moreover, the possible occurrence of backflow and scalability challenges which could occur in non-optimized systems are also discussed. Hence, the results of this review give an insight for upcoming SCPP designers to develop efficient and cost-effective plants.