Multi-Objective Optimization of Solar Thermal Systems Applied to Portuguese Dwellings

Ana Cristina Ferreira,José Carlos Teixeira,Senhorinha Teixeira,Angela Silva

doi:10.3390/en13246739

Ana Cristina Ferreira, José Carlos Teixeira + Show 2 more

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https://doi.org/10.3390/en13246739

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Abstract

Solar thermal systems have been widely used to increase energy efficiency in the building sector, since the use of renewable energy sources became one of the top priorities to meet environmental targets. The main objective of this study is the thermo-economic optimization 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 Non-dominated Sorting Genetic Algorithm-II (NASGA-II). The solar collection area and the linear loss coefficient as well as the tank storage volume were defined as decision variables. A two-dimensional Pareto front was obtained, considering as objective functions the minimization of the annualized investment cost and the maximization of the solar collection efficiency. Based on the best trade-off between both objectives and considering that the solar thermal systems can operate for a period of at least 15 years, the Pareto analysis led to the conclusion that a system with an annualized investment cost between 270 and 280 €/year allows reaching a collection efficiency of 60%. After the analysis of the optimal solution points, a configuration was selected to estimate the system total purchasing cost: a panel with a solar area of 4.17 m2 and with a linear coefficient loss of 3.684 W/m2.K; a storage volume of 0.275 m3; and a pump flow rate of 0.1364 m3/h. For this configuration, we estimated a total purchasing cost of 2545.0 €, whereas the solar collector and the storage tank are the most expensive components, representing a share of 42% and 43%, respectively. These results represent a specific cost of 610.3 €/m2 per solar collection area.

Highlights

Solar energy is the most abundant and cleaner renewable energy resource and it can be supplied with minimal environmental impact
The geographical coordinates, the topography, and the climate conditions of a certain location are the three main parameters that affect the effectiveness of solar thermal systems in converting direct and diffuse radiation into useful energy [4]
The demand of solar thermal systems is estimated to grow by 20% per year, depending on the collector working area, availability of the solar radiation throughout the year, and the type of solar thermal systems [5]

Summary

Introduction

Solar energy is the most abundant and cleaner renewable energy resource and it can be supplied with minimal environmental impact. Sun uniformly sends solar radiation through space, but only about 1367 W/m2 reaches the Earth atmosphere [1]. The amount of solar energy received on a 1 m2 surface during a time interval can be calculated by integrating the irradiance over that time interval. This energy, called solar irradiation or insolation, has two main components: the direct and the diffuse solar radiation [1,2,3]. The geographical coordinates, the topography, and the climate conditions of a certain location are the three main parameters that affect the effectiveness of solar thermal systems in converting direct and diffuse radiation into useful energy [4].

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