Research For The Performance Of Solar Thermoelectric Generator System

Solar thermoelectric power generation(STEG)is an emerging green power generation technology,which can convert solar heat into electrical energy directly by the Seebeck effect of semiconductor.Compared with the traditional power generation technology,thermoelectric power generation has many advantages,such as no mechanical moving parts,simple structure,small size,light weight,no noise,no pollution and so on.And the solar energy has the advantages of getting no regional limit and unlimited power.Therefore,STEG technology is widely used in the military industry,the intelligent building and the other fields.In recent years,the STEG technology has attracted widespread attention by researchers all over the world.The domestic and overseas researchers have used theoretical analysis,experimental measurement and numerical simulation methods to study the STEG and their important achievements were published.While,many defects are still existed in mathematical model when researchers use the numerical method to study the STEG performance.For example,most studies using zero or one dimensional thermoelectric model.However,zero and one dimensional model usually ignore the three-dimensional temperature distribution within the thermoelectric devices,and this two models unable to realize the coupling of temperature field and electric potential field.So the precision of the above two models is difficult to guarantee.Moreover,many models have no actual heat sink or use convective heat transfer instead of heat sink.These implification does not reflect the real effects of heat sink on the STEG system performance.Based on the above studies,fistly,we establish a three-dimensional and steady-state model of STEG system coupling with thermoelectric power generation and heat sink.This model contains the main effects involved in the thermoelectric power generation process and couples the temperature field and electric potential field equations.So the precision of this model is higher than zero and one dimensional model.This model can also reflect the true effects of heat sink on the STEG performance.Then,we use this three-dimensional and steady-state model to sudy the influences of the coolant flow rate and the channel numbers of heat sink on the performance of STEG system.The results show that the heat sink strongly influences the power generation performance of the STEG system.In the conventional model which the cold end of STEG system is filled with heat sink channels,there is an optimum heat sink coolant flow rate that make the system achieve the best performance.Based on the above analysis and research,in this paper,we put forward a new concept of "heat sink channel coverage ratio" in order to design the new type of heat sink channels in the STEG system model.When the coverage ratio of heat sink channels is 1/5,that is,the heat sink channels is only arranged at the cold end of PN junction composed by P-type semiconductor and N-type semiconductor.When we use this new design of heat sink channels model,we can increase the coolant flow rate to improve the solar thermoelectric generator system performance.Moreover,this new model has many superiorities,such as effectively adapting to various coolant flow rates,reducing the consumption of pump power and manufacturing expense by heat sink.Finally,on the basis of the new design of the heat sink channel s,we make further study on the semiconductor geometric parameters which can make influence on the solar thermoelectric generator system.These factors include the number,the height and the cross section area of PN junction.The results show that the STEG system performance will be reduced duing to the decrease of the temperature difference between hot and cold end of PN junction.The decrease of the temperature difference caused by the decrease of the heat of one PN junction under the condition of solar energy heat is fixed in the STEG system.As a result,it is not the more the better for the number of PN junction.When the other geometrical parameters of PN junction remain unchanged,an optimal PN junction height or cross-sectional area can be found to make the STEG system have best performance.