Optimizing thermoelectric generator efficiency by using maximum power point tracking and a passive cooling system.
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This project focuses on the improvement of a Thermoelectric generator’s (TEG) efficiency by the use of a maximum power point tracker (MPPT) and a designed passive cooling system. A TEG is a solid-state device that converts temperature difference between its cold and hot terminals directly into electrical energy. The phenomenon on which the TEG can perform this operation is called the Seebeck effect. TEGs have many advantages which include producing electrical energy from renewable energy sources, having no movable parts and long-life span. Despite these many advantages, TEGs are limited by their low levels of efficiency which is about 5 % for a small-scale TEG. To improve this efficiency, we employ two techniques which are integrating a circuit that performs MPPT and designed passive cooling system. The purpose of the circuit that performs MPPT of this circuit is to extract the maximum possible power from the TEG therefore ensuring that the load always receives the maximum possible power from the generator. The purpose of the passive cooling system is to keep the cold side of the TEG at a relatively low temperature so that a large temperature gradient is maintained between the cold and hot side. This would intern allow the TEG to convert more thermal energy to heat energy. This would increase the output power of the TEG, therefore improving its efficiency. A model of the conventional TEG is simulated in MATLAB based on the finite volume model and its efficiency calculated, the efficiency was 5.28 %. A circuit that performs MPPT is designed in Simulink, the code that is responsible for the maximum power tracking is also written in a MATLAB function block and then integrated with the circuit. The circuit is then integrated with the TEG simulation and the efficiency of 8.12% was observed. An appropriate passive cooling system was then designed based on a thermosiphon and fabricated in the workshop. The circuit that performs MPPT was fabricated. The physical system was integrated and tested under various conditions over a period of time with a locally available stove as the heat source and the maximum efficiencies determined. The efficiency of the MATLAB simulated TEG module was 5.28%. However, this efficiency increased to 8.12% when the module was integrated with the MPPT simulated circuit. The efficiency of the conventional module was determined by running tests on the prototype in intervals of 10 minutes. The maximum efficiency obtained from tests of the TEG module alone with heat from a charcoal stove was 5.49%. When the test was carried out with the passive cooling system, the maximum efficiency obtained was 7.53%. The maximum efficiency from the tests with the TEG module integrated with MPPT and the cooling system was 8.11%. Therefore, integrating the TEG with MPPT and a cooling system helps to optimize the TEG’s performance through the improvement of its efficiency. Some of the recommendations for this project are; Insulation of the conducting rod to improve safety and reduce heat loss to the surrounding and research in non-corrosive material for the prototype. It is also recommended for one to use a stable heat source for the TEG to obtain the best performance out of the TEG because with a charcoal cookstove. This is because power increases to a point and gradually reduces due to the burning out of the charcoal.