HEAT TRANSFER IN CONCENTRATED SOLAR POWER SYSTEMS By

HEAT TRANSFER IN CONCENTRATED SOLAR POWER SYSTEMS By Nick Smith

INTRODUCTION Concentrating Solar Power Systems (CSPs) focus a large area of sunlight onto a small area. Unlike photovoltaic systems, the sun's energy is not directly converted to electricity. Instead it is used to heat a fluid to steam, which in turn powers a turbine.

INTRODUCTION (CONT. ) Parabolic Solar Trough Power Plant in Israel

SCHEMATIC DRAWINGS

OBJECTIVE Use a simplified Heat Transfer Approach to find the optimum fluid, and length of the parabolic trough.

ASSUMPTIONS Radiation from the sun can be approximated (normalizing for the earth's surface area) as 680 W/m 2 Parabola perfectly reflects energy and can be approximated as a semi-circle Flow-rate is 0. 2 kg/s q” is evenly distributed across the tubing Fluid enters tube at ambient temperature, 20°C Effects of the tubing material are negligible To function properly, the average fluid temperature at exit should be 400°C

APPROACH The heat flux on the tube is equal to the solar heat flux over a semi-circle of 2. 5 m diameter

CALCULATIONS A simple energy Lengths of various balance equation will materials, using now give us the ideal average Cp: length for each Water: 130 m potential fluid: Oil: 71 m Mercury: 3. 85 m

CONCLUSIONS While Mercury would be the ideal material, it is hazardous and expensive, so oil should be used, as it is almost twice as efficient as water. More precise calculations should be done using different types of oil to find the most ideal material, perhaps a mixture with mercury would provide the best properties.

APPENDIX A more complete of heat transfer in CSP systems is available here: http: //pointfocus. com/i mages/pdfs/saltwtroughs. pdf Pictures and drawings are courtesy of Andrew Buck, modified by myself