Session: 05-02: Concentrating Solar Power I -- Heliostats and Trough Receivers

Paper Number: 130019

130019 - Optical Analysis and Optimization of a New Receiver for Solar Parabolic Trough Collectors (Detective) 

Abstract: 

DETECTIVE (Development of a novEl Tube-bundlE-CaviTy lInear receiVEr for CSP applications) is a project that aims at enhancing the overall performance of the current solar parabolic trough collectors by increasing the optical and thermal efficiencies of the absorber part. The proposed design focuses on enhancing performance through a bundle of tubes instead of conventional tubes, with two key objectives. Firstly, it seeks to reduce the diameter of each absorber tube, thereby increasing solar intensity. In the new design, the traditional tube with an outer diameter of 70 mm is replaced with a cluster of narrower tubes, bundled together to maintain an equivalent outer diameter of 70 mm. Secondly, it aims to improve solar absorption by incorporating a cavity-shaped arrangement of the tube bundle within an evacuated glass envelope. To optimize solar gain and since the conventional Parabolic Trough Collector (PTC) systems typically receive the peak concentrating flux on the lower sections of their tubular absorbers, the new design introduces an aperture opening from the bottom portion. This innovative feature transforms the entire tube bundle into a cavity receiver, where multi-reflection within the cavity significantly enhances flux absorption while reducing radiation losses from the narrow tubes. Solar rays enter the internal space between the tubes and become trapped inside, contributing to multi-reflection between the tubes. It is worth noting that to maintain consistency with conventional solar absorbers and minimize retrofitting costs, all other components, such as the flexible bellows and glass cover, remain unaltered. To assess the optical performance of the proposed receiver, a Monte Carlo Ray Tracing technique was employed by utilizing the SolTrace software. This approach allowed for analyzing the detailed flux distribution on each individual absorber tube. The effects of the two design parameters, such as cavity opening angle and tube outer diameters, on the overall optical performance have been explored and the optimum design determined with the maximum optical efficiency. The ray tracing data proved that the cavity-like space formed with the tube-bundle arrangement has resulted in a multi-reflection process between narrow tubes and would suggest higher ray absorption compared to the conventional design, leading to lower optical losses. Moreover, the different local concentration ratio (LCR) leads to an increased total accumulated power per unit length with respect to conventional PTC designs. Computing the total accumulated power per unit length showed that the optimum design has resulted in a considerable optical enhancement, increasing the amount of power from 35 kW in conventional PTC designs.

Presenting Author: Hossein Ebadi Politecnico Di Torino

Presenting Author Biography: Hossein is a Ph.D. student enrolled in the Energy Department at Politecnico di Torino. He joined the MAHTEP research group in 2020, working on the development of highly efficient receivers for solar high-temperature systems. Based on his experience in teaching and research at Shiraz University, he has expertise in solar energy engineering including process simulation (heat and mass transfer) and applied thermodynamics for modeling, designing, and testing solar collectors for residential and agricultural applications. After joining PoliTo, he has been working on numerical simulations using CFD analysis in the field of concentrating tubular receivers with a special interest in non-imaging concentrators. His latest research revolves around the application and optimization of a novel porous medium for CSP plants, operating with gaseous fluid at high temperatures.

Authors:

Hossein Ebadi Politecnico Di Torino
Diego-César Alarcón-Padilla Plataforma Solar de Almería
Juan José Contreras Keegan Absolicon Solar Collector AB
Rafael Eduardo Guedez Mata KTH Royal Institute of Technology
Silvia Trevisan KTH Royal Institute of Technology
Loreto Valenzuela Gutiérrez Plataforma Solar de Almería
Eduardo Zarza Moya Plataforma Solar de Almería
Laura Savoldi Politecnico di Torino