Amélioration du rendement énergétique des amplificateurs de puissance microondes par conversion et recyclage de l'énergie thermique

Abstract

This study consists in designing of a system for recovering and recycling the thermal energy dissipated from a RF power amplifier to improve its energy efficiency. This system is based on a thermoelectric converter and a power adapter: the thermoelectric converter is a planar microgenerator (μTEG) that converts the heat flux received from the amplifier into electrical energy using the Seebeck effect, the power adapter is composed of a DC/DC converter controlled by an MPPT controller, which couples the recovered electrical power with the power supply of the RF power amplifier. The efficiency of the proposed microgenerator is optimized using a new thermoelectric model for planar structures established by thermal-electrical analogy, the model shows that this efficiency depends essentially on the figure of merit of the used materials and the dimensions of the microgenerator topology. This approach was applicated for three microgenerators using three different thermocouples. Analytical simulations shows that a μTEG composed of a N-P Bismuth telluride (Bi2Te3) thermocouple provides the highest efficiency (3.5%) than a μTEG composed of Ag-Ni (0.016%) or TAGS75 (0.5%), due to its high figure of merit (ZT = 0.0066), which makes it the most suitable material for converting thermal energy. This approach was compared to a numerical Multiphysic simulation using COMSOL® for a μTEG based on (Ag-Ni) thermocouple, furthermore, to figure out the heat distribution on its topology, as well as the time evolution of the effective gradient. These simulation’s results show that our thermoelectric model can estimate the same behavior of the μTEG’s efficiency as given by the numerical simulations. The last part of this thesis investigated on the coupling of the recovered electrical power with the amplifier (operating at temperature’s level below <100 ° C) using a power adapter. The complete system was set up on SIMULINK® environment. The simulation results show that this adapter enhances the recovered electrical power from the μTEG (based on the N-P Bi2Te3 thermocouple) to reach 24.5 mW instead of 7.7 mW generated without this device, which leads to the improvement of the RF power amplifier efficiency by 0.75%.

Date	28 Feb 2019
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Ammar B. Kouki (Supervisor)