A SENSOR ELEMENT FOR DIRECT-RADIATION MEASUREMENT

A combination of a photodiode with a nonimaging light concentrator is developed to perform measurements of the direct solar radiation compon ent. A prototype composed of low price elements is taken as a starting point to discuss the problems which must be faced when calibrating su ch sensors. By this the influence of the angle of incidence and spectr al distribution (caused by different air mass or varying degree of cle arness) of the incident radiation on the behavior of the system is stu died. The readings are compared to the calculated (global minus diffus e) readings obtained from two standard star pyranometers. Finally the possibilities for increasing the accuracy of the sensor element and fo r applying the device are discussed. (C) 1998 Elsevier Science Ltd. Al l rights reserved.