Modelling of thermoelectric generator with heat pipe assist for range extender application

Abstract

Recent trends towards electrification of vehicles favour the adoption of waste energy recovery into electricity. Battery-only Electric Vehicles (BEV) need a very large energy storage system so the use of a Range Extender (RE) may allow a significant downsizing of these bulky components. The Internal Combustion Engines (ICE) have two major discarded energy fluxes, engine cooling and exhaust gas. In Extended Range Electric Vehicles (EREV) and hybrids the potential for heat conversion into electricity is particularly convenient. The direct conversion of thermal energy into electricity, using Thermoelectric Generators (TEG) is very attractive in terms of complexity. However, current commercial TEG modules based on Seebeck effect are temperature limited, so they are unable to be in direct contact with the exhaust gases. A way to downgrade the temperature levels without reducing its potential is to interpose Heat Pipes (HP) between the exhaust gas and the modules. This control of maximum temperature at the modules is achieved by regulating the pressure of phase change of the HP fluid. Such design is convenient for engines with large thermal load variations, such as the RE being developed by the team, with a low (15kW) and a high (40kW) power mode of operation. This system will be able to operate efficiently in both modes. The present work presents the thermal modelling of such a system in order to assess the suitability of this approach. This work is complemented with the experimental work being carried out by the team in this subject, already with some published results. The model was validated with experimental data with a good correlation. Therefore, it was possible to demonstrate the potential of this system for wasted heat recovery.