A ray tracer model for analysis of solar concentrating systems

Keywords: reflectors; receivers; flat mirror tiles; smooth mirror surfaces; interception ratio

Abstract

This study describes a 3D ray tracer model for analysis of a small-scale solar concentrating system where thermal heat is collected for cooking purposes. Emitted sun rays were traced from the source through all reflections until they intercepted with the receiver or were lost. The algorithm of the ray tracer and its implementation in MATLAB is clearly described. The ray tracer was programmed to contribute to the development of small-scale concentrating solar energy systems with integrated heat storage units. The ray tracer was demonstrated for selected cases where continuous reflecting surfaces and flat mirror-tiled surfaces were compared. Off-focus sensitivity analysis was shown and this could provide guidelines for the required solar tracking accuracy. The flux distribution on the absorber was analysed and found to be concentrated on a small area on the target for continuous reflecting surfaces and having high intensities. However, for reflectors with mirror tiles, an elongated image was formed centred on the focal point with low intensities. Small misalignment of the reflector in the order 0.2° had minimal impact on the interception ratio, but any further increase in the tracking errors caused a sudden drop in the interception ratio to zero. Results showed that there is close agreement in flux distribution and the tracking error impact on interception ratio, when compared with the literature. This model could be a useful tool when designing the reflection and absorption components of solar concentrators for complex systems with several components in a non-symmetric 3D arrangement.

Author Biographies

Karidewa Nyeinga, Department of Physics, Makerere University

Karidewa Nyeinga holds a PhD from Makerere University and MSc. degree in Physics from the Norwegian University of Science & Technology, NTNU, Trondheim, Norway. His main research area is solar energy with specific focus on solar thermal energy storage for cooking in rural areas and solar PV power plants. Currently, he is employed as a lecturer at the Department of Physics, Makerere university

Denis Okello, Department of Physics, Makerere University

Dr. Okello is a senior lecturer, Department of Physics, Makerere University.

Ole Jorgen Nydal, Department of Energy and Process Engineering, NTNU-Trondheim P.O Box-7491 Trondheim-Norway

Ole Jorgen Nydal, MSc., Dr. Scient (PhD)

Professor,

Department of Energy and Process Engineering,

NTNU-Trondheim

P.O Box-7491 Trondheim-Norway

Email: ole.j.nydal@ntnu.no

Tel: +4797715994

 

Ole Jorgen is a professor at the Department of Energy and Process Engineering, NTNU, Trondheim-Norway. His main research areas and professional activities include management of NTNU Multiphase Flow Laboratory and associated research group, contract research management, 1D computational methods for dynamic multiphase pipe flows with non-equilibrium thermodynamics, programming (procedural, object oriented, interactive, graphical), laboratory experiments on multiphase flow, flow assurance and concentrating solar thermal energy. He has published widely and supervised several PhD and MSc. candidates.

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Published
2019-03-08