Thermoelectric Performance Analysis Of The Solar-Driven TIC/AMTEC/TEG Hybrid System

Three kinds of static thermal to electrical conversion devices thermionic converter?TIC?,alkali metal thermal electric converter?AMTEC?,and thermoelectric generator?TEG?can convert heat energy into electric energy directly.They have many inherent characteristics and advantages,such as,good sealed performance,few movement parts,stable operation and so on.The three kinds of devices are incorporated into a novel thermoelectric hybrid system-TIC/AMTEC/TEG hybrid system.Not only are the output power and conversion efficiency of TIC/AMTEC/TEG hybrid system enhanced compared with subsystems,but also the heat energy can be utilized fully.The study of TIC/AMTEC/TEG hybrid system provides a theoretical basis for the future applications,and it is also of great academic value.A comprehensive theoretical model of solar-driven TIC/AMTEC/TEG hybrid system based on the first and second law of thermodynamics has been established for the first time.In the meantime,the calculation formulas of thermoelectric conversion efficiency,exergy efficiency,exergy loss and the ratio of exergy loss to total exergy loss have been deduced and their variation trends under the influence of load parameters?voltage output of TIC subsystem V₁,electrode current density of AMTEC subsystem J₂,dimensionless current of TEG subsystem i?were discussed.Besides,the exergy loss in each part of hybrid system was analyzed and the largest part was found.The results indicate that the variation trends of thermoelectric conversion efficiency(?_ALL??_TIC??_AMTEC)are similar with the exergy efficiency(?_xALL??_xTIC??_xAMTEC).And their maximums are one-to one achieved in the same V₁ and J₂.?_TICIC and?_xTICTIC increase with the increasing of V₁ and J₂.It is worth to mention that the increasing rate of?_xTICTIC increases with the increasing of V₁ when J₂ is small.And it is obvious for?_xTICTIC to increase with J₂ when V₁ is small.The maximal?_TICIC and?_xTICTIC are equal to 39%and 46%,respectively,when V₁=0.9V,J₂=4000A/m².Decreasing V₁ or increasing J₂ can both increase?_AMTECMTEC and?_xAMTEC.?_xAMTECAMTEC increases first and then decreases with the growing of V₁ when J₂ is small.With the increasing of J₂,?_xAMTECAMTEC decreases gradually with the growing of V₁.The maximal?_AMTECMTEC and?_xAMTECAMTEC are equal to 32%and 40.5%,respectively,when V₁=0.5V,J₂=4000A/m².?_ALLLL and?_xALLALL are decided by TIC and AMTEC subsystem mainly.The smaller of J₂,the greater of increasing rate of?_xALLALL with V₁.?_xALLALL increases first and then decreases with the growing of V₁ when J₂increases.The maximal?_ALLLL and?_xALLALL are equal to 55%and 64%,respectively,when V₁=0.9V,J₂=2800A/m².Furthermore,i shows influences on?_TEGEG and?_xTEGTEG only and its impacts on?_TIC??_xTIC??_AMTEC??_xAMTEC??_ALLLL and?_xALLcan be ignored.In addition,the exergy loss in AMTEC subsystem is the largest in three subsystems and its ratio of exergy loss to total exergy loss of TIC/AMTEC/TEG hybrid system is more than 90%.The exergy loss of AMTEC subsystem decreases with increasing V₁ and i,and decreasing J₂.But its exergy loss is still number one among three subsystems.The largest exergy loss in AMTEC subsystem is BASE.Hence,we should focus on increasing the performance of BASE in order to increase the capability of thermoelectric conversion in TIC/AMTEC/TEG hybrid system.