Multi-objective Optimization of Solar Thermal Systems Applied to Residential Building in Portugal

Abstract

Thermal-economic evaluation represents an effective tool to optimize thermal systems. This study presents a mathematical model that encloses the physical variable equations and a set of equations that define the purchase cost of the main system components. The main objective of this study is the thermo-economic optimisation of solar thermal systems for residential building applications, considering a multi-objective approach. The simulations were performed through a MatLab code, by implementing an elitist variant of NASGA-II. The numerical model disclosed a Pareto front considering the optimal trade-off solutions for the minimum investment cost and the maximum solar collection efficiency. The optimal solutions disclose a set of optimal solutions for which the solar collection efficiency vary 28.3% and 77.0% and the investment costs vary between 2,099€ and 3,308€. Results show that gains in solar collection efficiency above 70% imply a great increase in the total purchase cost, implying a bump of almost 1,000€, from a total investment cost of 2,200€ to 3,200€. As a conclusion, the solar collector area is one of the most important decision variables in the multi-objective optimization of thermal-economic analysis of solar thermal systems.