Thermoelectric Generators in Heavy-Duty Vehicle Applications: Development Approach and Optimization under Real Driving Conditions

Abstract

Despite technological progress such as advances of the internal combustion engine, heavy-duty vehicles are responsible for a large share of emissions from road transport in the European Union due to the high annual mileage and the increase in freight transport. For this reason, carbon dioxide limit values will be introduced for the first time in this market in the near future, including a 30% reduction in carbon dioxide emissions from new vehicles in 2030 compared with the reference year 2019 [1]. Against this background and the pressure to avoid fines, technological innovations are essential to meet these emission limits. Increasing the efficiency of modern heavy-duty vehicles represents an important approach. At this time, about 2/3 of the chemical energy of the fuel is lost through waste heat in roughly equal proportions via the coolant and exhaust system of the engine. A waste heat recovery system offers the potential to increase efficiency in order to reduce fuel consumption and thus emissions. Waste heat recovery systems in the form of a thermoelectric generator offer an attractive solution with low system complexity. Based on the Seebeck effect, thermoelectric generators convert the existing thermal energy of the exhaust gas directly into electrical current. Integrated into the exhaust gas system of the vehicle, thermoelectric generators can convert a part of the previously unused energy for supplying the on-board electrical system or charging the battery and relieve the alternator. The system advantages are low maintenance costs, low system weight, small installation volume and a competitive as well as an economical cost-benefit ratio. For this reason, this paper presents the system design of a thermoelectric generator in modern Euro VI heavy-duty vehicles. The objective of the procedure is to demonstrate that the system can meet the challenging economic requirements with regard to the total cost of ownership. This requires an efficient system design. Therefore a holistic perspective with the specific analysis and consideration of the limited cooling capacity shall be presented. The development and optimization is carried out using a model-based design approach and a multi-domain simulation under stationary and dynamic boundary conditions.