Receiver Loss Study; Optics of Optimized Solar Central Receiver Systems as a Function of Receiver Thermal Loss Per Unit Area. Final Report

摘要

Recent efforts in solar central receiver research have been directed toward high temperature applications. Associated with high temperature processes are greater receiver thermal losses due to reradiation and convection. This report examines the performance of central receiver systems having optimum heliostat fields and receiver aperture areas as a function of receiver thermal loss per unit area of receiver aperture. The results address the problem of application optimization (where the loss per unit area varies) as opposed to the problem of merely optimizing a design for a specific application (where the loss per unit area is approximately fixed). A reasonable range of values for the primary independent variable L (the average reradiative and convective loss per unit area of receiver aperture) and a reasonable set of design assumptions were first established. The optimum receiver aperture area, number and spacings of heliostats, and field boundary were then determined for two tower focal heights and for each value of L. From this, the solar subsystem performance for each optimized system was calculated. Heliostat field analysis and optimization required a detailed computational analysis. A significant modification to the standard method of solving the optimization equations, effectively a partial decoupling of the solution process into collector and receiver subsystem parts, greatly aided the analysis. Results are presented for tower focal heights of 150 and 180 m. Values of L ranging from 0.04 to 0.50 MW/m exp 2 were considered, roughly corresponding to working fluid temperatures (at receiver exit) in the range of 650 to 1650 C. As L increases over this range, the receiver thermal efficiency and the receiver interception factor decrease. The optimal power level drops by almost half, and the cost/unit of energy produced increases by about 25% for the base case set of design assumptions. (ERA citation 10:023693)