Waste heat is inevitable in any human endeavour. Thus, the need to develop thermal energy conversion systems. Thermoelectric generators (TEGs) are solid-state devices that convert waste heat to useful electricity. They have found various applications in converting solar energy to electricity, harvesting exhaust waste heat in automobiles and power plants and providing power for spacecrafts by converting the heat released during radioactive decay to electricity. Despite these perks, they are characterised by very low efficiencies. Thus, several efficiency enhancement strategies such as material modification and leg geometry alteration have been introduced. Pertaining the latter, the trapezoidal shaped geometry has been studied extensively. Although it offers a higher efficiency compared to the conventional rectangular leg geometry, it still exhibits higher thermal stresses and consequently, a reduced lifespan. A conical frustum shaped TE pin has not been conceived yet. The investigation of this leg geometry is important since it might provide a higher efficiency and operating lifetime compared to the current trapezoidal leg. Thus, a thoroughly validated numerical model is used in evaluating the performance of three TEGs comprising rectangular, trapezoidal and conical frustum shaped TE legs. Results indicate that the proposed conical frustum leg TEG enhances the power density and exergy efficiency of the trapezoidal device by 20% and 23%, respectively. Also, the thermal stress and thermodynamic irreversibilities of the trapezoidal leg TEG are reduced by 2% and 0.5%, respectively.
Keywords conical frustum, solar thermoelectric generator, heat transfer analysis, exergy efficiency, thermal stress, thermodynamic stability.