Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Many rural communities in developing countries still do not have access to electricity, however, inhabitants of those communities must still perform energy demanding activities. Such is the case of milling grains to fulfill their food intake. This activity, in many cases, is still performed manually.
This research project aims in providing a solution to the aforementioned problem by designing, implementing and testing a grain mill powered solely by means of photovoltaic energy. It is intended to avoid the use of an intermediate battery in order to reduce the initial and possible running costs of the solution.
The project development included testing the operation of the mill under different speeds and loads to acknowledge the torque profile and accurately size the corresponding motor. A brushless direct current motor together to its speed controller was selected to drive the mill. The operation of the mill was tested under constant and variable power source to characterize the electrical performance and size a suitable photovoltaic module. Also, the quality of the flour and output rate were analyzed.
A modified maximum power point tracker controller was designed and implemented based on a microcontroller (Arduino Uno board). The perturb and observe as well as the incremental conductance maximum power point tracking methods were implemented and analyzed to be used as the basis of the modified tracking algorithm.
The overall performance of the designed controller was evaluated using a modified test procedure based on the EN 50530 standard, which indicates how to evaluate the static and the dynamic efficiency of the maximum power point trackers in grid connected inverters.
The proposed controller achieved an average static efficiency of 47 % while milling corn and 55 % while milling wheat, based on the weighting factors defined in the European efficiency. Moreover, the controller reached an average dynamic efficiency of 50 % while milling corn and 62 % while milling wheat during the test with irradiance change from medium to high levels (300 W/m2 to 1000 W/m2). Finally, the average flour output rate while milling corn was measured as 3.25 kg/h while milling corn and 5.38 kg/h while milling wheat.
2018.