DETERMINATION OF ERROR TOLERANCES FOR THE OPTICAL DESIGN OF PARABOLIC TROUGHS FOR DEVELOPING-COUNTRIES

A study is presented where potential optical errors in parabolic troughs are divided into two groups: random and nonrandom. Small-scale slope errors, mirror specularity, apparent changes in sun's width, and small occasional tracking errors are classified as random errors. Reflector profile errors, misalignment of the receiver with the effective focus of the reflector, and misalignment of the trough with the sun are classified as nonrandom errors. Random errors are analyzed using statistics and assuming a normally distributed error. Nonrandom errors are analyzed by building provisions into the optical model which allow for the analysis of such errors. Universal design curves showing the effect of random and nonrandom errors on the optical performance (efficiency) of the trough are presented. The optimum range of rim angles in the presence of both random and nonrandom errors is found to be between 105 degree and 120 degree .