Summary
In this study, the first time in the literature, natural zeolite has been employed for photovoltaic thermal (PVT) and experimentally tested as a thermal energy storage material. The main aim of the paper is to introduce natural zeolite as a heat storage material for PVT systems. The PVT systems integrated with phase change materials and natural zeolite were designed, the components of the system were explained, the thermodynamical modelling including the first and second laws was presented, the system performances were evaluated, performance parameters were investigated, energy and exergy efficiencies were determined, and economical analyses of each system were performed. Besides, all results were compared with a conventional PVT system. The average overall energy efficiency values for PVT experiments were 33% for paraffin, 37% for stearic acid, 40% for zeolite, and 32% for conventional PVT systems. The payback period of the PVT system with paraffin, zeolite, stearic acid, and conventional PVT was calculated as 10, 8, 9, and 9 years, respectively. The results show that the natural zeolite is a material with significant potential to be used for heat management in PVT for any meteorological condition.
SUMMARYTransmission of concentrated solar energy via fibre-optic bundle (FOB) has a great potential for numerous applications. In this paper, it is aimed to determine the transmission performance of a constructed plastical FOB-based solar lighting system. The experiments and measurements are carried out by means of a metal halide source simulating the spectral distribution of solar radiation in visible range of wavelength. Optical efficiency, luminous efficacy, attenuation, spectral characterization under different bending conditions, integration of optical filters and FOB were investigated. The effects of the optical filter proposed are discussed for a solar lighting system. Spectral and colour properties of FOB and the optical filter are also presented.
In this article, it is aimed to determine the daylight availability and luminous efficacy of global irradiance for Izmir, which has Mediterranean climatic conditions. Daylight availability and luminous efficacy were put forward by using existing valid models, including Aydinli Model, Perez Model, and IESNA Model. Yearly exterior illuminance levels have been estimated by the use of hourly data of the Meteorological Station of Solar Energy Institute. The models were compared in consideration with their luminous efficacies. Monthly average hourly exterior daylight illuminance levels estimated by Aydinli Model, Perez Model, and IESNA Model were put forward for Izmir. Frequency distributions of luminous efficacies (lm/W) for hourly values calculated by these theoretical methods were evaluated. The frequency distributions were examined in consideration with the reference value referred to in the literature. Yearly correlations between hourly average daylight illuminance by Aydinli Model, global illuminance by Perez Model, daylight illuminance by IESNA Model, and measured hourly global solar irradiance were established and determined to be able to estimate daylight availability data for Izmir. According to these correlation equations, it is shown that the linear correlation coefficients (R 2 ) are 0.9536 for Aydinli Model, 0.9994 for Perez Model, and 0.9747 for IESNA Model. Finally, the potential of daylighting and the feasibility of natural lighting systems for Izmir were evaluated according to these results.
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