| Thermoelectric power generation is based on semiconductor thermoelectric materials,which can directly convert heat energy into electric energy.It has the advantages of small volume,lightweight,no moving parts,no pollution,and no noise.It is a valuable environmental protection and energy-saving technology.There are many kinds of available heat sources in the vehicle system.By combining with thermoelectric power generation technology,the heat in the vehicle system can be recovered and converted into electric energy to assist the vehicle drive or supply power for electrical appliances,which can improve the vehicle fuel economy.However,the existing thermoelectric power generation systems are constrained by the disconnection between material synthesis research and actual device development.Nowadays,slow iteration of device structure and process,and lack of global optimization at the system level,resulting in low energy conversion and energy utilization efficiency.Therefore,based on the characteristics of the heat sources available in the vehicle system,improving the synthesis method of thermoelectric materials and device manufacturing process,designing a reasonable energy management strategy are important for the improvement of the energy conversion efficiency of the system.Under the support of the general project of the National Natural Science Foundation of China"Multi-field coupling mechanism and energy dynamic planning research of automobile exhaust thermoelectric power generation system under variable working conditions"and the strategic innovation project,"IOT environmental sensor system for thermoelectric power generation at room temperature"of Japan New Energy Industry Technology Development Institute,this thesis takes the thermoelectric power generation system applied to vehicles as the research object.The research goal of this thesis is to improve the energy efficiency of automotive thermoelectric power generation.The main research contents of this thesis focus on thermoelectric material synthesis,device development,and energy utilization.In addition,the thermoelectric power generation system is expanded into three research modules:energy conversion,energy transfer,and energy management.The research methods of analytical modeling,simulation calculation,prototype trial production,and experiment are conducted in this thesis to build a research scheme which consists of theoretical analysis,material synthesis,structural design,and energy management strategy optimization.The main contents of this thesis are as follow:(1)The thermoelectric power generation system is deconstructed and analyzed from three modules:energy conversion,energy transfer,and energy management.Firstly,based on the constitutive equation and energy conservation equation of thermoelectric power generation,a one-dimensional analysis model of thermoelectric power generation is constructed,and a thermoelectric power generation size optimization method based on thermal resistance model is proposed.The influence of contact thermal resistance and thermoelectric leg size on the energy conversion efficiency of thermoelectric power generation are analyzed.Then the energy transition circuit of thermoelectric power generation is built,the main factors affecting energy efficiency in the process of energy transition are analyzed,and the common maximum power tracking strategies are summarized.It lays a foundation for further research on energy conversion and energy efficiency optimization of the thermoelectric power generation system.(2)The main factor affecting the energy conversion efficiency of thermoelectric power generation systems is the performance of thermoelectric materials.According to the features of different automotive thermoelectric generators,a thermoelectric material synthesis scheme based on the electrodeposition method is determined.The processes of substrate preparation,electrolyte configuration,electrodeposition process operation,and synthetic material transfer are described.In this thesis,a high-performance p-type thermoelectric material synthesis scheme based on multi additives is proposed.The morphology characteristics and lattice distortion of p-type thermoelectric material under the influence of multi additives are analyzed.Based on the performance evaluation platform of thermoelectric materials,the effect of multi additives on the performance optimization of thermoelectric materials is verified,and the optimization mechanism is revealed.(3)The energy conversion analysis model of thermoelectric power generation device is established,and the relationship between thermoelectric material performance and device energy conversion efficiency under different boundary conditions is discussed.Considering the heat transfer modes of different automotive heat sources,a flat thermoelectric generator and a new interdigital planar thermoelectric generator are designed for vertical heat transfer and lateral heat transfer respectively.The performance of the traditional planar thermoelectric generator and new structure are compared and analyzed by finite element calculation.The process flow chart of the new structure is designed,the process of each step are described in detail.The prototype is trial produced and its performance is tested.At the same time,to improve the maximum power density,the size and layout of the thermoelectric legs of the new planar thermoelectric generator are optimized.(4)The vehicle exhaust thermoelectric power generation device is developed,and the test platform is built to test the transient and steady-state output performance of the device.In order to optimize the energy utilization efficiency of vehicle exhaust thermoelectric power generation,a mild hybrid electric vehicle with exhaust thermoelectric power generation is studied.Considering the influence of the thermoelectric power generation device on the whole vehicle system,the vehicle longitudinal dynamic equation based on the working characteristics of the thermoelectric generator is established.The switch method of vehicle driving mode is improved,and the energy management strategy is optimized.The theoretical research and experimental analysis show that:(1)With the development trend of vehicle electrification and intelligence,the application space,and energy-saving potential of thermoelectric power generation technology in vehicle systems can be expanded and improved.According to the different characteristics of multiple heat sources in vehicle systems,the comprehensive optimization of thermoelectric power generation systems has important theoretical significance and practical application value.(2)Electrodeposition technology can synthesize thermoelectric materials with different dimensions,which is suitable for the development of thermoelectric devices designed for different automotive heat sources.In this study,p-type Bi Sb Te-based thermoelectric materials with compact structure,high performance,and high thickness were successfully synthesized by adding polyvinyl alcohol,saccharin sodium,and potassium chloride.The power factor at room temperature reaches 834?W/m K~2.(3)Based on the method of electrodeposition synthesis of thermoelectric materials,flat thermoelectric generator and planar thermoelectric generator were successfully developed.The open-circuit voltage of the flat plate thermoelectric generator reaches 48.3 m V/K.When the temperature difference is 10 K,the maximum power density reaches 12.2?w/cm~2.(4)Considering effects of automotive exhaust thermoelectric power generation device on vehicle system,and improved vehicle driving mode switch method is proposed.Under different vehicle test driving cycles,the fuel economy is improved by 3.64%and 2.17%respectively.The energy utilization efficiency of thermoelectric power generation in vehicle system is improved. |
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