Design of a Thermoelectric Generator for Harvesting Brake Heat Energy for a Rail Vehicle
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Date
2019-06
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Addis Ababa University
Abstract
We live in an era where energy needs are increasing daily, fossil fuels are reducing and yet also renewable energy source development still has a long way to go. Systems that run on energy do not use the available energy as efficiently as we would want to. Despite the continued efforts to improve system energy efficiencies, too much energy is still being lost in different forms especially in the form of heat. During the vehicle braking process, all the energy is converted into heat energy at the brake disc. This wasted energy presents a problem to be tackled in order to improve resource efficiency. This thesis investigates the use of thermoelectric generators (TEGs) as a means of recovering this energy. A TEG, working on the principle of Seebeck effect converts heat energy into electrical energy directly. Heat simulations were done for a brake disc using temperature as the input gave an input temperature of 160 0C and also heat flux in the case of repeated braking which gave an average input temperature of 261.5 0C. A model of a TEG was developed in 3D by SOLIDWORKS and applied to a brake disc of a railway vehicle to use the brake heat to generate power. Furthermore, by simulation using ANSYS, a parametric study was performed on the influence of voltage increase, the number of legs and the size of the legs. Based on the data acquired, the effects of changing voltage, current, leg size as parameters were noted and discussed. Here, heat absorbed at the hot junction and the energy generated were considered. Based on this data the TEG’s system efficiency and TEG’s recovery efficiency are calculated and discussed. From the design made, a device recovery efficiency of 2.94% of heat lost per second was achieved which amounts to 67 kW per vehicle per braking. In the case of repeated braking, a 5% recovery efficiency was achieved. The results obtained in this thesis allow the drawing of essential conclusions with regards to the overall TEG system performance which are essential to further studies.
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Keywords
Braking, Disc brake, Thermoelectricity, Thermoelectric generator, Waste heat energy, Energy harvesting