Optical analysis of a beam-down linear Fresnel reflector coupled with a flat plate receiver

Christos Sammoutos; Evangelos Bellos; Angeliki Kitsopoulou; Panagiotis Lykas; Evangelos Vidalis; Dimitra Gonidaki; Dimitrios N. Korres; Christos Tzivanidis

doi:10.47248/ges2606030007

Green Energy and Sustainability 2026;6(3):0007 | https://doi.org/10.47248/ges2606030007

Original Research Open Access

Optical analysis of a beam-down linear Fresnel reflector coupled with a flat plate receiver

Christos Sammoutos ¹ , Evangelos Bellos ² , Angeliki Kitsopoulou ¹ , Panagiotis Lykas ¹ , Evangelos Vidalis ¹ , Dimitra Gonidaki ² , Dimitrios N. Korres ¹ , Christos Tzivanidis ¹

1. Department of Thermal Engineering, School of Mechanical Engineering, National Technical University of Athens, Zografou, Heroon Polytechniou 9, 15780 Athens, Greece
2. Department of Mechanical Engineering, School of Engineering, University of West Attica, 250 Thivon & Petrou Ralli, Egaleo, 12244 Athens, Greece

Correspondence: Christos Sammoutos

Academic Editor(s): Tony Roskilly, Georgios Martinopoulos, Georgia Kastrinaki, Hande Eryilmaz, Martin Roeb

Received: Jul 31, 2025 | Accepted: Apr 27, 2026 | Published: Jun 3, 2026

This article belongs to the Special Issue Selected Papers from the Conference ICRES 2025

Cite this article: Sammoutos C, Bellos E, Kitsopoulou A, Lykas P, Vidalis E, Gonidaki D, Korres DN, Tzivanidis C. Optical analysis of a beam-down linear Fresnel reflector coupled with a flat plate receiver. Green Energy Sustain. 2026;6(3):0007. https://doi.org/10.47248/ges2606030007

Abstract

Beam-down concentrating solar systems consist of two successive reflections. Compared to the conventional concentrated configurations, there are two concentrators, and the receiver is on the ground level. In the present study, a beam-down linear Fresnel reflector is investigated in optical terms. The collector is a conventional flat plate receiver. Two different secondary concentrators are examined and compared based on their optical performance. Both the secondary concentrators are hyperboloidal, intending to enhance the optical performance. The first concentrator examined has a parabolic shape. The second concentrator examined consists of flat segments, which are designed based on the parabolic profile of the previous parabolic secondary concentrator, aiming to reduce the configuration’s construction cost. The major objective of this work is to conduct an optical analysis of the proposed configurations and calculate the optical performance, the incident angle modifier, and the intercept factor for various incident angles. The maximum value for optical efficiency was calculated at 68.6% and refers to the flat-segmented design, a promising value for a concentrating solar system.

Keywords

Beam-down linear Fresnel reflector, Flat-segmented secondary reflector, Parabolic secondary reflector, Optical investigation

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