Economic-environmental evaluation and multi-objective optimization of supercritical CO2 based-central tower concentrated solar power system with thermal storage

We address the optimal design of central tower-concentrated solar power (CSP) system combined with supercritical CO2 Brayton cycle and thermal storage under economic and environmental objectives. The economic objective is measured by the levelized cost of electricity (LCOE), and the environmental objective by the power plant's total environmental impact potential (TEIP) considering the system's global warming, acidification, and eutrophication emission. A multi-objective mixed-integer nonlinear programming (MINLP) model is developed that takes into account the main characteristics of CSP plant, e.g. unit operations, working fluid thermodynamics, equipment sizing, thermal storage capacity. Life cycle assessment and economic evaluation of the manufacturing, construction, operation and decommission stages of the systems are also embedded in the model. The multiobjective MINLP problem is solved by a tailored algorithm, and the resulting Pareto solutions are analyzed to identify the tradeoffs between the economic and environmental performance. The proposed approach is illustrated through a case study of a 50 MWe CSP plant. Results show that the framework is able to obtain the system's economically-environmentally optimal design in reasonable time. A minimum LCOE of 115.82 $/MWh can be achieved for the most cost-effective design, and a minimum TEIP of 320.54 x 10(3) mPE(90) can also be achieved for the most environmentally friendly design. A 'balanced' solution is identified with an LCOE of 116.89 $/MWh and TEIP of 330.29 x 10(3) mPE(90). Numerical studies also reveal that while the Brayton cycle only accounts for a small proportion of the total investment, spending more on enhancing the efficiency of its equipment is cost-effective to improve the overall economic and environmental performance of the system.