A handbook for solar central receiver design

Abstract

Central receiver systems use sun-tracking mirrors called heliostats to concentrate direct normal solar insolation on a receiver located atop a tower. Only solar energy capable of casting a shadow may be used for concentration. The concentrated energy is used to heat a receiver fluid to high temperatures. T h e collected solar energy may he employed for the generation of electricity or for the production of process heat.

Optical and thermal performance of bladed receivers

“…Falcone [1] notes that different working fluids have different characteristic flux limits: for water, it is around 600 suns; for molten salt, around 850-1000 suns; for sodium, around 1300-1750 suns. Limitations arise due to thermal stresses, creep, corrosion and cyclical fatigue, as well as stability limits on the working fluid (around 600°C for molten salt) [1]. Peak flux limitations are more challenging in the hottest parts of a receiver, since excessive flux can too easily cause tube or working fluid temperatures to be exceeded [5].…”

“…Peak flux limitations are more challenging in the hottest parts of a receiver, since excessive flux can too easily cause tube or working fluid temperatures to be exceeded [5]. Current molten salt receivers operating near these various flux limits typically achieve a receiver efficiency of the order of 90% [1,5].…”

“…In central tower systems with significant storage, these receivers predominantly use molten salt as the working fluid. A constraint on these systems however is the peak flux limitation which, together with spillage and optical considerations, limits the minimum receiver area [1].…”

Codes for solar flux calculation dedicated to central receiver system applications: A comparative review

“…Thermal and economic algorithms are incorporated to enable optimization, performance and design studies of the complete plant. Three of these codes are dedicated to the optical subsystem (Falcone, 1986): -NS (cellwise performance) provides interception and flux data, diurnal and annual flux data for fixed designs. The solar field is divided into cells corresponding to regions with uniform heliostat density or fixed number of heliostats, or single heliostats and performance is calculated for a representative heliostat in each cell (Lipps and Vant-Hull, 1978), -RCELL (cellwise optimization) optimizes solar components (heliostat spacings in field, field boundaries, tower and receiver dimensions) on cost/performance criteria obtaining interception factors for the optimization from a very simple model (for initial trials) or for accurate results from NS outputs (''node files''), -IH (individual heliostat layout and performance code) is a detailed layout processor using RCELL data to specify each heliostat location and can also compute performance for each heliostat or for the whole field.…”

“…By generating and using data bases (''cosine, shading, and blocking files'' and ''node files'') computing time is saved (Falcone, 1986). UHC codes have been used to optimize heliostat fields and to evaluate optical performance of a number of CRS, including solar one and solar two.…”