CONSTRUCTION OF LOCALLY MADE PYRHELIOMETER FOR DIRECT SOLAR IRRADIANCE MEASUREMENT

Abstract

This work presents the design, construction and testing of a low cost Pyrheliometer for tracking direct normal irradiance. A collimating tube with two concentrating lens of focal length 22cm each was used to focus the direct solar radiation onto a receiving photodiode sensor; known as BPW34 on the receiver disk. A Pyrheliometer needs to follow the sun throughout the day, that is, from sunrise to sunset to measure direct beam irradiance. In order to achieve this, an inexpensive tracking system capable of autonomous operation was designed with two DC motor and programmed using Arduinor mega 2560 with the required accuracy. The tracking system enables the Pyrheliometer to operate as a stand-alone-system. The designed system was use to carry out measurement for fourteen days, the measured data was compared to data obtained from satellite. The average correlation coefficient (r) and coefficient of determination (r2) obtained are 0.961 and 0.9806 respectively.