Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Flomo N. Kokro - California State University, Los Angeles
A Solar Thermal Concentration System (STCS) uses a mirror in the shape of a parabolic half-cylinder to reflect and concentrate solar radiation on a collector tube located at the focus line. The collector, a cylindrical double-walled vacuum tube, traps the incident concentrated sunlight and reaches temperatures in excess of 450˚F. It may either be filled with water to create hot water/steam directly, or may house copper or aluminum heat exchangers and a working fluid to transfer the heat to water. The system may be used either as a water heater, or to generate steam and power an engine/generator.
Key to the efficient working of the parabolic concentrator is that the parabola be oriented so that the solar rays are normal to the half-cylinder, i.e. the sun lies along the vertical ‘y’ axis of symmetry of the parabola. The 24-hour rotation and seasonal movement of the earth’s axis around the sun means that the cylinder must be gimbaled in two dimensions to maintain optimal alignment with the sun. A solar-tracking actuator system must be installed along the gimbal axes to rotate the STCS using either photo-sensors (or more sophisticated power-measurement and neuro-algorithms) for feedback control, or an open-loop system that uses astronomical data to precisely predict the correct orientation of the sun relative to the system at any instant time of day.
My research employs a technique called Ray Tracing to focus on three practical questions: (i) how does the accuracy of tracking impact the efficiency of the system, (ii) which ‘size’ parabola of given cross-sectional area yields the least sensitivity to tracking errors, and (iii) how efficient are easier-to-build shapes such as circular cross-section and even conical collectors employing the same type of collector tube, especially when these are used in fixed orientation? Addressing these questions should point the way towards low-cost and more rugged solar concentrator systems with acceptable efficiency.KokroFlomoERNAbstract.docx
Funder Acknowledgement(s): CSULA LSAMP-BD Cohort XI is supported by the NSF via Grant #HRD-1363399.
Faculty Advisor: Samuel Landsberger, firstname.lastname@example.org