Experimental and numerical investigation of the aperture size effect on the efficient solar energy harvesting for solar thermochemical applications. (1st March 2015)

• Record Type: Journal Article
• Authors: Sarwar, J.; Georgakis, G.; Kouloulias, K.; Kakosimos, K.E.
• Is Part Of: Energy conversion and management. Volume 92(2015)
• Page Start: 331
• Page End: 341
• Publication Date: 2015-03-01
• Subjects: Heat transfer -- Ray tracing -- Variable irradiance -- High flux solar simulator; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2014.12.065
• Languages: English
• ISSNs: 0196-8904

Abstract

Highlights: Experimental results on thermal analysis of a solar cavity for variable apertures. Development of an optical model for energy transfer from light source to the cavity. Development of a coupled ray tracing and heat transfer model for the cavity. Validation of both the models with experimental measurements. Use of the models to study new cases like the efficiency of the variable apertures. Abstract: In this paper, experimental and numerical work have been undertaken to investigate the steady state temperatures throughout the day of a cylindrical solar receiver when using fixed and variable size apertures. A high flux solar simulator, consisting of a 7 kW xenon short arc lamp, is employed as a light source. The sunlight intensity variations at early morning (06:30), morning (07:15) and noon (12:00) time of a reference day are imitated by changing the input current to the lamp. Experiments have been performed with different aperture diameters across selected irradiance levels to imitate sunlight variations. An optical model is developed to simulate incident flux distribution and the output is compared with the experimental measurements for validation. A finite volume algorithm is developed, based on a coupled Monte Carlo heat transfer model, to calculate the steady state temperatures in the receiver. Experimental and numerical temperatures are compared and an excellent agreement with an average temperature difference of ±0.2%, is observed. The optimum aperture size varies with the change in irradiance intensity and therefore the time of day. Simulations for a 30 kW light source show that the daily steady state temperature differential for fixed apertures of 8–10 cm is 170–190 K. Variable apertures reduce power consumption by half when compared to fixed apertures. Variable apertures maintain steady state temperatures of 1000 K, 1100 K and 1200 K by consuming 26.8 kW day, 33.2 kW day and 26.9 kW day, respectively.