Journal of Solar Energy Research

Upgrading Solar Thermal Performance with Engine Oil in Evacuated-Tube Collectors for Sustainable Energy Solutions

Document Type : Research Article

Authors

1 Ministry of Higher Education and Scientific Research/Scientific Research Authority, Iraq

2 Technical Instructor Training Institute, Middle Technical University, Baghdad 10074, Iraq

3 Petroleum Engineering Department, College of Engineering, University of Kerbala, Karbala 56001, Iraq

4 Al-Naji University, Baghdad 10015, Iraq;

5 College of Administrative and Financial Science, Gulf University, Sanad, 26489, Kingdom of Bahrain

10.22059/jser.2025.404409.1657

Abstract

The high-demand for solar power systems has stimulated research efforts to find better heat transfer fluids for evacuated tube solar collectors (ETSCs). This research aims to appraise the thermal characteristics of an ETSC, which utilises engine oil as a heat transfer vehicle within a new efficient system beyond conventional flat-plate collectors. Temperature elevation under solar radiation becomes rapid because the evacuated tube contains engine oil with Grade 20-w50, which possesses a high-boiling point of >350 °C and heat transfer properties including 2.5 kJ/kg K heat capacity and 88 kg/m³ density. Experiments are conducted for different ranges of solar radiation intensity with different ranges of engine oil temperatures. According to the results, this system reacts swiftly to solar radiation changes and reaches a maximum temperature of 198 °C at a solar radiation of 800 w/m2, which makes water evaporation and superheating possible. More importantly, in comparison to traditional flat-plate collectors, this collector demonstrates a high conversion efficiency and quick response to the influencing parameters. The introduced approach not only enhances energy efficiency but also brings into line with the United Nations Sustainable Development Goal (SDG 7) to deliver reasonable and clean energy solutions to conflict climate change and improve sustainable industrialization.

Keywords

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Journal of Solar Energy Research
Volume 10, Issue 4
October 2025
Pages 2691-2701