Fabrication Of Micro-thermoelectric Devices And Investigation Of Geothermal-thermoelectric Coupled Air Conditioning System

Thermoelectric devices（TEDs）,including thermoelectric generators（TEGs）and thermoelectric coolers（TECs）based on the Seebeck and Peltier effect respectively,are capable of converting heat into electricity directly and vice versa.Because of its all-solid-state nature with pollution-free,no moving part,and no chemical reaction,TEDs have been found many applications,such as the remote power source for spacecraft,solid state refrigerators,waste heat recycling,and so on.In particular,on-chip integrable micro-thermoelectric devices（μ-TEDs）,which can realize local thermal management,on-site temperature sensing,and energy harvesting under minor temperature gradient,could play an important role in biological sensing and cell cultivation,self-powered Internet of things（Io T）,and wearable electronics.Ground-source heat pump is a kind of refrigeration/heating technology,which uses the geothermal resources stored in the surface（about 47%of the solar radiation energy）and takes the land shallow soil or groundwater as the cold/heat source for energy conversion.The soil and water on the surface is a huge dynamic energy balance system,which can naturally maintain the relative balance of energy absorption and emission.The temperature keeps around 18℃at all time.Using it as a cold/heat source makes the geothermal air conditioning system have higher refrigeration and heating coefficient.This paper focuses on thermoelectric devices,mainly divided into two aspects.In the first part,based on micro electro mechanical machining（MEMS）technology,we explored the fabrication process ofμ-TEDs,using the electrochemical deposition method to synthesis compact N-type and P-type thermoelectric materials,and explored the patterned growth technology.In the second part,we report a prototype of a geothermal-thermoelectric coupled air conditioning system（GTAC）.The commercial Bi₂Te₃ based thermoelectric devices were used as the heat pump through the Peltier effect to compensate the low-grade heat energy in geothermal resources.Compared with traditional vapor compression air conditioning systems,the GTAC is a simpler system without compressor,expansion valve,and refrigerants such as CFCs and HCFCs,which eliminates the possibility of environmental damage caused by refrigerant leakage.In addition,the separate and personalized thermal energy management of GTAC terminals can make rational use of geothermal resources and effectively avoid the waste of electric energy.The experimental results show that the performance of the engineering prototype is good.the cooling capacity of the prototype is 631 W,and the corresponding COP is 1.77,when the input power is 350 W and the ambient temperature is 25℃under the cooling mode.When switch to heating mode with input power is 350 W and ambient temperature is 18℃,the heating capacity and COP of the prototype is 590 W and 1.65,respectively.