Thermoelectric Generators for Heavy-Duty Vehicles as an Economical Waste Heat Recovery System

Abstract

Fuel consumption and emissions from heavy-duty vehicles account for a large proportion of emissions of road transport and without further innovation, significant reductions are unlikely. Part of this problem is that about 2/3 of the chemical energy of the fuel is lost in the form of waste heat via the engine coolant and exhaust system. Thermoelectric generators offer a solution with low complexity and a competitive cost-benefit ratio. In this research study, a holistic modelling approach including all vehicle interactions is used for analysis and optimisation. Conventional heavy-duty commercial vehicles with diesel and innovative natural gas vehicles will be investigated. The holistic design with modern simulation methods allows the evaluation of the technology based on fuel and emission reduction and payback period for future commercial vehicles. The results of the system are highly dependent on the load point and the application profile of the vehicle. For the diesel heavy-duty vehicle, the fuel reduction is in a range of 0.5–1.5 % and the amortisation period varies between 1.4 and >10 years at maximum electrical output of the generator under different dynamic driving conditions in the range of 180–1900 W. For the natural gas vehicle, the fuel reduction is in the range of 1.8–2.6 % and the amortisation period is between 0.7–2.5 years with output powers in the range of 1950–3150 W. In addition, the power density of the systems was determined to be 241 W/dm3 in diesel and 568 W/dm3 in natural gas vehicles, which represents a significant increase compared to the state-of-the-art. The lowest cost-benefit ratio is achieved by 85 EUR/(g km) for the diesel and 32 EUR/(g km) for the natural gas heavy-duty vehicle. Thermoelectric waste heat recovery technology can be interesting for vehicle applications with gasoline, diesel, natural gas, hydrogen combustion engines and fuel cells, among others.