Investigation On The Performance Optimization Of Alkali Metal Thermal Electric Converter Coupling Systems And Energy Selective Electron Devices

The need for new energy technologies has been paid attention from the perspective of global energy demand and the increase in greenhouse gases and pollution.For decades,renewable energy sources(such as solar and wind)have played a key role,but their intermittent nature could lead to a serious mismatch between supply and demand.Electrochemical energy systems play a key role in energy sustainability,energy conversion,conservation and storage,pollution control/monitoring,and in greenhouse gas reduction.The alkali metal thermoelectric converter(AMTEC)is an electrochemical device which utilizes heat from a solar,a nuclear source or fossil fuels to generate electricity.It is an excellent device for converting heat into electricity.In this paper,the coupling systems,in which the waste heat generated by the AMTEC is,respectively,utilized by the thermoelectric generator(TEG),Brayton engine(BHE),and AMTEC,and the direct carbon fuel cell(DCFC),solid oxide fuel cell(SOFC),and solar concentrator are,respectively,used as the heat source of the AMTEC,are studied by computational simulation.This paper not only evaluates the performance characteristics of these systems,but also gives the parameter selection criteria.In addition,a refrigerator or a thermal amplifier system composed of three electronic reservoirs in different connective methods and a thermal amplifier system composed of four electronic reservoirs are studied in this paper.The research contents of this paper mainly include the following three parts.The first part includes chapter 2.In order to make full use of the waste heat released from the low temperature region of the AMTEC,the three coupling systems of the AMTEC are established,where the AMTEC is,respectively,coupled with three thermodynamic systems,i.e.,the AMTEC-TEG system,AMTEC-BHE system,and two-stage AMTEC system.The analytical expressions of the efficiencies and power outputs of the coupling system are derived.The influence of electrolyte thickness and other main parameters on the overall performance of the coupling systems and the matching problem of two subsystems are discussed.The optimal regions of the coupling systems and the selection criteria of main parameters are determined.The optimal performance of the existing AMTEC coupling system is compared with that of the single AMTEC.It is found that the performance of the coupling systems is better than that of single AMTEC and the performance of the AMTEC-BHE system is superior to that of the other two coupling systems mentioned above.The second part includes chapters 3,4,and 5.To reveal the influence of different heat sources on the performance of AMTECs,the new models of the AMTEC driven,respectively,by the DCFC,SOFC,and solar concentrator are established.The various main irreversible losses are taken into account.The expressions for the efficiencies and power outputs of several systems are derived.The efficiency and power output of each system are taken as objective functions.The whole performance of the system is optimally analyzed.The boundaries and the optimal regions of the efficiency and power are determined.The optimum selection criteria of main parameters are provided.The optimum theories of the AMTECs driven,respectively,by several different heat sources are established.The results obtained can promote the development of AMTECs.The third part includes chapters 6 and 7.A thermal amplifier or a refrigerator consisting of three-terminal energy selective electronic(ESE)devices and a thermal amplifier composed of four-terminal ESE devices are established.A three-terminal ESE device may have three different wire connection ways and six different electronic transmission forms.Every connection way can be regarded as the equivalent system composed of an ESE heat engine and an ESE heat pump/refrigerator.The maximum coefficient of performance and heat-pumping/cooling rate are calculated.The optimally operating regions of systems are determined,and the optimal performances of the systems with three connection ways and two configurations of energy filters are compared.The thermal amplifier composed of four electron reservoirs and four energy filters is further established.It is equivalent to a coupling system composed of two three-electron reservoir heat pumps.The maximum heat-pumping rate and coefficient of performance are calculated.It is found that the maximum heat-pumping rate of the coupling system can attain 2 times of that of a three-electron-reservoir heat pump while its maximum coefficient of performance still remains the same as that of a three-electron-reservoir heat pump.The effects of the half width of energy filters on the heat-pumping rate and coefficient of performance are discussed in detail.The cut-off value of the half width of energy filters is calculated.The results obtained in this thesis not only enrich the research contents of the above thermodynamic systems,but also have certain reference value for the optimal design and actual operation of relevant thermodynamic systems.