Performance Evaluation of an Evacuated Tube Collector with a Low-Cost Diffuse Reflector

Julian Schumann, Bert Schiebler and Federico Giovannetti
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Julian Schumann: Institute for Solar Energy Research Hamelin (ISFH), Am Ohrberg 1, 31860 Emmerthal, Germany
Bert Schiebler: Institute for Solar Energy Research Hamelin (ISFH), Am Ohrberg 1, 31860 Emmerthal, Germany
Federico Giovannetti: Institute for Solar Energy Research Hamelin (ISFH), Am Ohrberg 1, 31860 Emmerthal, Germany

Energies, 2021, vol. 14, issue 24, 1-16

Abstract: In order to increase the overall solar energy gain of evacuated tube collectors, rear-side reflectors are used. In this way, the otherwise unused incident radiation between the tubes can be reflected back to the absorber, and the performance of the collector can be improved. In this paper, the use of a low-cost, diffusely reflecting, trapezoidal roof covering made from a galvanized metal sheet is investigated and compared to a high-quality, specularly reflecting plane reflector made of aluminum. For this purpose, ray-tracing analysis and TRNSYS simulations were carried out. In the ray-tracing analysis, the experimentally determined zero-loss collector efficiency η 0 as well as the incident angle modifiers for each reflector can be reproduced with an error lower than 7.5%. Thermal system simulations show that the performance of both reflectors is comparable. The use of the low-cost reflector leads to an increase in annual collector output of around 30% compared to an increase with the specular reflector of around 33%. Considering a typical domestic hot water system, both reflectors enable an increase in the solar annual yield of approx. 11%.

Keywords: solar thermal; evacuated tube collector; diffuse reflector; specular reflector; TRNSYS; ray tracing (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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