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Energies
Volume 19
Issue 1
10.3390/en19010007
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Article

Experimental Evaluation of a Solar Ejector Cooling Cycle Prototype †

by
Konstantinos Braimakis
1,
Tryfon C. Roumpedakis
2,*,
Spyros Kalyvas
1,
Gabriel Palamidis
2,
Antonios Charalampidis
2,
Efstratios Varvagiannis
2 and
Sotirios Karellas
2
1
Laboratory of Refrigeration Air Conditioning & Solar Energy, National Technical University of Athens, 15780 Zografou, Greece
2
Laboratory of Thermal Processes, National Technical University of Athens, 15780 Zografou, Greece
*
Author to whom correspondence should be addressed.
†
This paper is an extended version of our paper published in ECOS2024 International Conference, Rhodes, Greece, 30 June–5 July 2024; pp. 1375–1386.
Energies 2026, 19(1), 7; https://doi.org/10.3390/en19010007
Submission received: 18 November 2025 / Revised: 12 December 2025 / Accepted: 16 December 2025 / Published: 19 December 2025
(This article belongs to the Special Issue Advanced Heating and Cooling Technologies for Sustainable Buildings)
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Abstract

Ejector-based cooling systems have gathered scientific interest as a low-cost alternative for solar-assisted cooling applications, especially in regions with solar abundance. This work presents the experimental investigation of a solar ejector cooling prototype system. The system, developed at the National Technical University of Athens, includes a custom-made ejector and is powered by a 48 m2 flat plate solar collector field, assisted by an auxiliary natural gas boiler. Experimental testing under varying operating conditions was conducted to assess the system’s performance, focusing on the influence of evaporation and condensation temperatures. The maximum coefficient of performance (COP) was measured at approximately 0.160–0.165, corresponding to an entrainment ratio of 0.19 at an evaporation temperature of 9 °C and condensation temperatures of 26–27 °C. Ejector performance substantially declined with increased condensation temperatures. However, the influence of the evaporator pressure on system performance was less significant. These findings demonstrate the feasibility of ejector-based solar cooling as a sustainable solution for reducing electricity use in cooling applications, highlighting the critical influence of operating parameters in the system’s performance optimization.
Keywords: ejector cooling; solar cooling; test rig ejector cooling; solar cooling; test rig

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MDPI and ACS Style

Braimakis, K.; Roumpedakis, T.C.; Kalyvas, S.; Palamidis, G.; Charalampidis, A.; Varvagiannis, E.; Karellas, S. Experimental Evaluation of a Solar Ejector Cooling Cycle Prototype. Energies 2026, 19, 7. https://doi.org/10.3390/en19010007

AMA Style

Braimakis K, Roumpedakis TC, Kalyvas S, Palamidis G, Charalampidis A, Varvagiannis E, Karellas S. Experimental Evaluation of a Solar Ejector Cooling Cycle Prototype. Energies. 2026; 19(1):7. https://doi.org/10.3390/en19010007

Chicago/Turabian Style

Braimakis, Konstantinos, Tryfon C. Roumpedakis, Spyros Kalyvas, Gabriel Palamidis, Antonios Charalampidis, Efstratios Varvagiannis, and Sotirios Karellas. 2026. "Experimental Evaluation of a Solar Ejector Cooling Cycle Prototype" Energies 19, no. 1: 7. https://doi.org/10.3390/en19010007

APA Style

Braimakis, K., Roumpedakis, T. C., Kalyvas, S., Palamidis, G., Charalampidis, A., Varvagiannis, E., & Karellas, S. (2026). Experimental Evaluation of a Solar Ejector Cooling Cycle Prototype. Energies, 19(1), 7. https://doi.org/10.3390/en19010007

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