Microcontroller based data acquisition and control of a solar thermal energy system.
Doho, Gonçalves Justino.
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A solar thermal energy system is being rebuilt at University of KwaZulu-Natal School of Physics. A similar system is also being built in the University Eduardo Mondlane – Maputo Mozambique, in a team development work. The system is composed mainly of the following subsystems: (i) An Energy capture subsystem: paraboloidal dish concentrator with a heat receiver, mounted on a dual axis polar mount sun tracking assembly; (ii) An Energy storage subsystem: rock-bed thermal energy storage (TES) system; (iii) An Energy utilization subsystem: any user heat utilization (like a cooking or water boiling appliance); and (iv) A monitoring and control subsystem. The subsystem (iv) for performing a controlled charging of the Thermal Energy Storage from a hot plate simulated solar heat, was formerly developed and it was based on 2 conventional data loggers (HP/Agilent) and programs running on 2 PCs. The present work is aimed at performing the same plus additional monitoring and control tasks, based on a low cost microcontroller design. The monitoring and control subsystem based on the Atmel ATmega 32 MCU has been designed and built, capable of performing data acquisition, data logging and control of relevant system variables such as, hour and declination angles of the tracking concentrator; to cite some of the main variables. Besides a huge work of designing, building, programming and testing the microcontroller system itself, a special focus was given to the monitoring and control of the solar heat concentrator, to perform a dual axis sun tracking, so as to get as much as possible of the available solar radiation. Measurements of various system parameters such as, the sun tracking actual hour and declination angles, the inlet and outlet temperatures of both the heat receiver and the rock bed heat storage, etc., for the system under consideration have been carried out.