Resumen de Photovoltaic thermal concentrator optimized for solar cooling and heating applications
Bahy Saad Abdallah Abdel Mesih
This thesis focuses on the characteristics of the Fresnel concentrating prototype BiFres 22. BiFres 22 is a system that uses mirrors to concentrate the incoming sun rays 22 times on photovoltaic modules. Water runs beneath the cells to cool them down thus producing hot water simultaneously with the electricity. The objective is to study the optical, thermal, and electrical aspects of the prototype. The study includes experimental work, theoretical modeling, and simulations. The long term objective is to show a system capable of producing electricity and heat at a competitive feasible cost for future market dissemination. Errors in the surface of mirrors of the concentrator affect the quality of the reflected rays and their distribution on the modules which affect the electrical efficiency of the solar cells. Therefore, a novel experimental method that involves photography and a geometrical algorithm, based on the principles of perspective, is formulated to analyze the produced images thus assessing the surface slope errors of the mirrors. The experimental work includes measurements of the real prototype concentration ratio, spectrometer tests on the reflectivity of the mirrors, illumination profile on the PV modules, and the thermal and electrical performance of the prototype BiFres 22. The quasi-dynamic test of the European standard EN 12975 is used for the modeling of the thermal output data of the prototype. The TRNSYS simulation environment is used to model the thermal and electrical experimental data. The TRNSYS analytical non-standard model 262 is tested and validated in order to simulate the performance of the BiFres 22 prototype. A parametric study is carried using this model to show the performance of the concentrator under various operating conditions and to compare it to flat plate collectors.The potential of using the heat generated from concentrated photovoltaic-thermal systems , which is a by-product, for solar cooling is an interesting application to extend the functions and usability of the generator. The aim is to see if linear concentrators at medium concentration ratios can fulfill the requirements to operate a solar driven absorption cooling machine or not. The outlet temperature of the photovoltaic thermal concentrator should be kept between 75 ºC and 95 ºC in order to operate the chiller and this affects the cells performance as their efficiencies degrade with the increase in temperature. Different configuration setups are investigated to connect both the concentrator and the chiller as well as different cold and hot storage tank sizes are studied for better understanding of the interaction between the various components of the system.
