טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentCohen Shay
SubjectDevelopment of a Spherical Solar Collector with a
Stationary Reflector/Tracking Absorber for
Industrial Process Heat
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Emeritus Gershon Grossman
Full Thesis textFull thesis text - English Version


Abstract

A system for collecting solar energy at high temperatures was developed and built in this  research project. The system, which was built at the Solar Energy Laboratory, the Energy  Engineering Research Center, Faculty of Mechanical Engineering of the Technion, consists  of a stationary, 120º included angle, 2.8 m diameter spherical reflector with a tubular,  tracking absorber which moves automatically into the focus following the sun's movement.

The system is capable of heating water or other fluids to temperatures above 200 degrees  Celsius, thus making it possible to obtain process heat for domestic and industrial use and to  store solar energy in a compact and economical way.

An analysis of the system's optical and thermal characteristics was performed to aid in the  design of the reflector and absorber.

The overall performance of the system has been analyzed in detail. Results of the study show that the efficiency of the collector is almost constant up to working  temperatures of 300 degrees Celsius. The analysis indicates that the optical properties of  mirror, glass envelope and absorber are the most important of the principal governing

parameters in determining system performance.

The particular feature of the new system, as compared to other concentrating collectors, is  that the reflector is stationary and can hence be produced by cheaper and simpler technology.

The performances of the spherical collector were tested under different weather conditions by  measuring the flow rate and the temperature of the pressurized water. Total efficiencies (solar  to thermal) of 30%-45% were obtained for a wide range of temperatures up to 200 degrees  Celsius. The simulations predict higher efficiencies of approximately 70% for a wide range of  temperatures up to 300 degrees Celsius.

The results of the present study show that it is possible to use the spherical collector in  cooling and heating systems and make possible a wide utilization of solar energy and  considerable savings relative to fossil energy in the sunny countries of the world.