Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Calorimetric Testing of Solar Thermal Absorbers for High Vacuum Flat Panels

Carmine D’Alessandro
,
Davide De Maio
,
Antonio Caldarelli
ORCID logo ,
Marilena Musto
,
Francesco Di Giamberardino
,
Matteo Monti
,
Teresa Mundo
,
Emiliano Di Gennaro
ORCID logo ,
Roberto Russo
* ORCID logo ,
Vittorio G. Palmieri
Version 1 : Received: 4 May 2022 / Approved: 7 May 2022 / Online: 7 May 2022 (02:52:12 CEST)

A peer-reviewed article of this Preprint also exists.

D’Alessandro, C.; De Maio, D.; Caldarelli, A.; Musto, M.; Di Giamberardino, F.; Monti, M.; Mundo, T.; Di Gennaro, E.; Russo, R.; Palmieri, V.G. Calorimetric Testing of Solar Thermal Absorbers for High Vacuum Flat Panels. Solar Energy 2022, 243, 81–90, doi:10.1016/j.solener.2022.07.039. D’Alessandro, C.; De Maio, D.; Caldarelli, A.; Musto, M.; Di Giamberardino, F.; Monti, M.; Mundo, T.; Di Gennaro, E.; Russo, R.; Palmieri, V.G. Calorimetric Testing of Solar Thermal Absorbers for High Vacuum Flat Panels. Solar Energy 2022, 243, 81–90, doi:10.1016/j.solener.2022.07.039.

Abstract

Among solar thermal collectors, the evacuated flat panel is emerging as a reference technology for operation at higher temperatures of up to 200 °C with an increased annual energy production owing to both direct and diffuse light capture. Accurate measurements of the optical properties of the selective absorbers used in such devices are key for a reliable estimation of the overall performance. These optical properties must be measured under high vacuum at high temperatures, conditions under which the panels are meant to operate. In this study, we accurately measured these properties using a calorimetric technique. The measurement procedure is based on a power balance equation for a flat sample suspended in a high-vacuum chamber with minimal thermal losses and is well adapted for this class of devices. Calorimetric measurements obtained under Sun and LED light revealed excellent reproducibility and good agreement with those obtained using traditional optical analysis at low temperatures in air. When extended up to the absorber stagnation temperature, which often exceeds 300 °C, the calorimetric measurements started to deviate from the optical measurements, indicating the importance of measuring under the operating conditions.

Keywords

Selective Solar Absorber; Solar Absorptance; Thermal Emittance; Evacuated Flat Panel; Calorimeter; High Vacuum Flat Panel; Solar Simulator

Subject

Physical Sciences, Applied Physics

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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