Assessment of an exhaust thermoelectric generator incorporating thermal control applied to a heavy duty vehicle

• Published in: Energies (Basel) 2022-07, Vol.15 (13), p.1-19
• Main Authors: Sousa, Carolina Clasen, Martins, Jorge, Carvalho, Óscar Samuel Novais, Coelho, Miguel Granja Pinheiro, Moita, Ana Sofia, Brito, F.P.
• Format: Article
• Language: English
• Subjects: Aluminum; Carbon dioxide; Diesel engines; Dilution; Emissions; Energy consumption; Energy efficiency; Exhaust gases; Exhaust systems; Flow rates; Fuel consumption; Fuel efficiency; Gas temperature; Gases; Heat; Heat exchangers; Heat recovery; Heat transfer; Heavy vehicles; heavy-duty vehicles; Mass flow rate; Onboard electricity production; Overheating; Phase change; Pollutants; Road transportation; Science & Technology; Thermal analysis; Thermal control; Thermal energy; Thermoelectric generators; Thermoelectricity; Transportation industry; Vapour chambers; Variable conductance heat pipes; Vehicles; Waste heat recovery; Wavy fins
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en15134787

The road transport industry faces the need to develop its fleet for lower energy consumption, pollutants and CO 2 emissions. Waste heat recovery systems with Thermoelectric Generators (TEGs) can directly convert the exhaust heat into electric energy, aiding the electrical needs of the vehicle, thus reducing its dependency on fuel energy. The present work assesses the optimisation and evaluation of a temperature-controlled thermoelectric generator (TCTG) concept to be used in a commercial heavy-duty vehicle (HDV). The system consists of a heat exchanger with wavy fins (WFs) embedded in an aluminium matrix along with vapour chambers (VCs), machined directly into the matrix, that grant the thermal control based on the spreading of local excess heat by phase change, as proposed by the authors in previous publications and patents. The TCTG concept behaviour was analysed under realistic driving conditions. An HDV with a 16 L Diesel engine was simulated in AVL Cruise to obtain the exhaust gas temperature and mass flow rate for each point of two cycle runs. A model proposed in previous publications was adapted to the new fin geometry and vapour chamber configuration and used the AVL Cruise data as input. It was possible to predict the thermal and thermoelectric performance of the TCTG along the corresponding driving cycles. The developed system proved to have a good capacity for applications with highly variable thermal loads since it was able to uncouple the maximisation of heat absorption from the regulation of the thermal level at the hot face of the TEG modules, avoiding both thermal dilution and overheating. This was achieved by the controlled phase change temperature of the heat spreader, that would ensure the spreading of the excess heat from overheated to underheated areas of the generator instead of wasting excess heat. A maximum average electrical production of 2.4 kW was predicted, which resulted in fuel savings of about 2% and CO 2 emissions reduction of around 37 g/km. This article was partially supported by projects COOLSPOT PTDC/EME-TED/7801/2020, UIDB/00481/2020 and UIDP/00481/2020 (Centre for Mechanical Technology and Automation—TEMA) and UIDB/04077/2020 (MEchanical Engineering and Resource Sustainability Center—MEtRICs)— Fundação para a Ciência e a Tecnologia (FCT); CENTRO-01-0145-FEDER-022083 (Centro2020), Norte2020, Compete2020, under the PORTUGAL 2020 Partnership Agreement, through Portuguese national funds of FCT/MCTES (PIDDAC) and the Europe