Thermo-economic investigation of transcritical carbon dioxide solar-thermal power plants, Part 2: Sensitivity analysis and comparison of alternative designs

• Thermodynamic analysis of a CO 2 solar-thermal power plant for medium-to-small-scale industrial/campus cogeneration applications. • Sensitivity analysis and four different alternative designs developed to test different improvements to the power plant. • Lowest levelized cost of energy of $ 0.2613/kWh achieved with higher cycle maximum temperature and medium-scale cogeneration. • A thermodynamic cogeneration efficiency of 50.7 % makes the supercritical Brayton cycle attractive for combined heat and power. • This technology is suitable where space constraints for the power block are demanding, and high temperatures are available. This paper presents the design-optimization and economic viability analysis of a carbon dioxide power cycle integrated with a parabolic trough collector solar-thermal plant. CO 2 cycles are the subject of ongoing research due to their potential advantages as compared to traditional steam cycles for power generation. Small-to-medium-scale combined heat and power application scenarios were investigated. A thermodynamic analysis helped identify the different power cycle configurations that were of interest due to applicability and potential economic benefits, namely: transcritical, recompression, and supercritical cycle configurations. First, a baseline transcritical plant was designed (presented in Part 1 of this study) and subjected to sensitivity analysis and empirical modeling validation. Then, four alternative designs with different power cycle configurations were developed: A, B, C, and D, with Alternative A being the baseline design. Alternative B achieved the lowest Levelized Cost of Energy (LCOE) of $ 0.2613/kWh. Sensitivity analysis results and alternative designs comparison enabled quantifying the impact on economic viability of key factors such as cycle temperatures, efficiencies, annual hours of operation, and capital costs. For instance, for every 10 % increase in the turbine efficiency, the LCOE is reduced by 9.5 %, while reductions in the largest capital costs of the power plant, i.e., the solar field and the power block, could potentially reduce the LCOE by 20 %. The supercritical cycle was found to be advantageous over the other cycle configurations for the applications studied. It was concluded that benefits in terms of performance, footprint and cost can make this technology increasingly competitive for cogeneration applications.