# Simulink Model of a Thermoelectric Generator for Vehicle Waste Heat Recovery
## 1 Introduction  
With the advent of the internal combustion engine (ICE) in the late 19 th century and its continued development during the 20 th century, humankind has benefited greatly from its use for transportation. In fact, the 20 th century can be defined in one word \"Mobility\"; local, regional, national, and international mobility of goods, people, and ideas. However, owing to its construction and general operation, the ICE manages to only partially transform fuel chemical energy into mechanical work. This is illustrated by the thermal efficiency of modern ICEs that generally only reaches 40-45%. This respectively low value of energy conversion directly influences the economic efficiency of the road transport process. For example, a 40 t freight vehicle with a payload of 25 t operating with an ICE has an overall transport process efficiency equal to 17-18% [1]. Furthermore, since transportation has a significant influence in both national and global economies, increasing transport process efficiency can immediately reduce operating costs while additionally helping to decrease greenhouse gas emissions. Most of the thermal energy of the ICE (approx. 30%) is lost through the high temperature combustion exhaust gases that are discharged directly into the atmosphere. Therefore one solution to increase overall efficiency is to recover, at least a part of this significant heat loss to the environment. For this purpose, research has targeted the design, development and implementation of thermoelectric generator modules for directly converting heat into electricity, which can then be used in hybrid power systems to increase vehicle efficiency. Thermoelectric devices are environmentally friendly and have numerous other advantages including the lack of moving parts, the conversion of thermal energy directly into electrical energy, high reliability, as well as low maintenance requirements. The main disadvantage of such devices is their low efficiency owing to the small dimensionless figure of merit (ZT) values currently found in commercial devices. However, there are promising solutions for achieving higher ZT values even at low to mid temperatures (<150 \({}^{\circ}\)C) [2]. The research efforts focused on identifying the potential for converting thermal energy into electricity, through thermoelectric generator (TEG) systems of different configurations and sizes, installed on the engine's exhaust path show that it is possible to obtain an electrical power output of approximately 200-1000 W, depending on vehicle type and operating conditions [3; 4; 5; 6]. However, research has also shown that the vehicular use of TEG systems depends on driving conditions with negative effects found when conditions have a high changing frequency [7]. The development of numerical models investigating the efficient use of TEG systems centers mainly on: Operating temperatures, optimizing geometric dimensions [8], different materials in TEG construction [9], and design optimization of hot and cold side heat exchangers [10]. Furthermore, TEG system design focuses on the energetic efficiency of conductive and convective system types [11]. In this area, [PERSON] et al. [12] proposed a numerical model to determine the optimum values for the thermocouple leg lengths and cross-sectional areas. Their analysis showed that, for given thermal boundary conditions, the maximum output power can be improved by optimizing the leg length or cross-sectional area. Other efforts by [PERSON] et al. [13] developed a mathematical model to investigate the effects of different vehicle engine operating regimes (e.g., cold-start and different loads) on TEG performance. The major conclusion of their research was that TEG performance is influenced more by vehicle speed than by ambient temperature. [PERSON] et al. [14] used a three-dimensional computational fluid dynamics simulation to analyze power output temperature distribution, and pressure drop of a TEG system with different internal structures of the heat exchanger.