Technoeconomic and environmental optimization of a solar tower integrated energy system for freshwater production

Abstract

A novel energy system consisting of a Brayton cycle, a heliostat field, an organic Rankine cycle and a multi-effect desalination-thermal vapor compression unit is proposed and investigated. Freshwater and electricity are the products of the proposed energy system. The present study proposes a sustainable renewable-based energy unit for freshwater production, and introduces a new concept of a pair plot, which can provide useful insights into the behavior of an energy system. A multi-objective optimization is conducted using NSGA-II with two objective functions (total cost and total exergy destruction rate) and ten decision variables. The point on the Pareto optimal solution nearest to the ideal point has a total exergy destruction rate of 4.7 MW and a total unit cost of 0.045 $/kWh. The scatter distribution and pair plot of the decision variables are illustrated and trends for each decision variable are discussed. The NSGA-II and NSGA-III performances are contrasted and compared by employing the hypervolume indicator technique. An NSGA-II genetic algorithm optimization with three objective functions is conducted and the results are discussed. The three objectives are total exergy destruction rate, total unit cost and gain output ratio. Also, the impact on CO2 emissions of the heliostat field is discussed, and a thermodynamic description of each model is developed and validated with numerical and experimental data.