Regulation of power generated from thermoelectric generators

Twaha, Ssennoga (2018) Regulation of power generated from thermoelectric generators. PhD thesis, University of Nottingham.

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Abstract

In recent years, the efficiency of thermoelectric devices has improved greatly due thermoelectric material and device geometrical improvements. However, the efficiency of TEG is still low, being a subject of further research for more improvement. Hence, the main objective of the research carried out in this thesis is to analyse the performance of dc-dc converters with or without MPPT in conditioning the power generated from TEG. In light of this objective, the following case studies have been carried out.

The initial study has analysed the performance of a TEG/dc-dc boost converter system. Results indicate that the converter is able to stabilise and boost the voltage and higher efficiencies are achieved at different hot side temperatures.

The next study proposes the use of MPPT algorithm to harvest maximum power from TEG system. Hence, the analysis of the performance of TEG/dc-dc converter with MPPT enabled by Incremental conductance (IC) method is done. The results indicate that the IC based MPPT approach is able to track the maximum power point but with relatively lower efficiencies than the Perturb and Observe (P&O) based MPPT method. method.

Another study has analysed the parameters for the performance of TEG/dc-dc converter system in different modes with a variable load. The TEG system is subjected to different hot side temperatures, including increasing step, increasing random and constant cold side temperature profiles. The study has demonstrated how the proper selection of converter components is a necessity to avoid converter losses as well interferences on the load connected to TEG/dc-dc converter system.

Furthermore, another study compares the performance of extremum seeking control (ESC) and P&O MPPT algorithms applied to TEG system. The TEG model is validated with results from multiphysics (COMSOL) modelling software. To assess the effect of temperature dependency of TEG parameters, two TEG materials have been chosen; bismuth telluride (Bi2Te3) with temperature dependent Seebeck effect (S), electrical conductivity (σ) and thermal conductivity (k); and lead telluride (PbTe) with non-temperature dependent S, σ and k. Results indicate that ESC MPPT method outperforms the P&O technique in terms extracting maximum power and the simulation speed. Results also indicate that ESC outperforms the IC technique in terms of extracting maximum power and the speed of computation. ESC method is faster than the IC method.

In the final study, the application of the concept and the design of a distributed dc-dc converter architecture (DCA) on TEG system is deliberated. The distributed or cascaded converter architecture involves the use of non-isolated per-TEG dc-dc converter connected to the load. Alternatively, for some specific loads, especially in automotive applications, soft-switched, isolated bi-directional dc-dc converters can be used instead of non-isolated converters because these integrated converters enable bi-directional power flow control capability. Simulations and experimental studies have been carried out to demonstrate and prove the necessity of the DCA design application on TEG systems. In addition, some of the factors affecting the performance of TEG systems are correspondingly analysed.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Jie, Zhu
Yuying, Yan
Bo, Li
Keywords: Thermoelectric generators; dc-dc converters; Maximum power point tracking (MPPT)
Subjects: N Fine Arts > NA Architecture
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Faculties/Schools: UK Campuses > Faculty of Engineering > Built Environment
Item ID: 49544
Depositing User: SSENNOGA, TWAHA
Date Deposited: 15 Mar 2018 04:40
Last Modified: 16 Mar 2018 15:42
URI: http://eprints.nottingham.ac.uk/id/eprint/49544

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