Optimizing thermoelectric generator efficiency by using maximum power point tracking and a passive cooling system

Abstract

A thermoelectric generator (TEG) is a device which converts temperature difference between two points directly into electricity. Thermoelectric generators (TEGs) are currently being used to harness energy from waste-heat from cook-stoves and industrial processes. A TEG module operates on principle of Seebeck effect, a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two materials. TEGs are a renewable energy source and are advantageous because they have long service lifetime, they are compact, completely silent and extremely reliable. However, the major challenge with use of TEGs is their relatively low efficiency e.g. efficiency about 5% for a conventionally small scale TEG module. This limits the application of TEGs for electrical energy applications compared to other renewable energy sources such as solar, hydro, biogas and wind. The purpose of this project was to optimize the efficiency of a TEG module by integrating a Maximum Power Point Tracking (MPPT) and passive cooling system with the module. MPPT is a technique used to maximize power extraction under all conditions. This technique was made as a computer based program (made in MATLAB for this project) that was used to control the behavior of the actual TEG module. The passive cooling system was designed and constructed in a workshop to implement the desired water based cooling function. A model to demonstrate the operation of both the MPPT and cooling system was built and tested to determine their effect on the efficiency of the TEG module. The heat source for the module in this project was a charcoal stove where by a heat conducting rod was used to conduct heat to the hot side of the TEG module. 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 program. The efficiency of the actual module was determined by running tests on the project’s prototype in intervals of 10 minutes for 70 minutes. The maximum efficiency obtained from tests of the actual 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%. This signifies that the addition of MPPT and a cooling system to the TEG resulted into an overall efficiency improvement of 47.7%. In conclusion, the project’s objective of optimizing the TEG’s efficiency by use of MPPT and a passive cooling system was achieved since the actual TEG’s efficiency improved from 5.49% to 8.11%. However, I recommend better heat insulation system for the heat conducting rod for safety purposes and to reduce heat loss to the surrounding. It is also better to use a more stable heat source in order to get more reliable results because charcoal stove is unreliable due to burning down of charcoal within an hour’s time.