Research On Thermoelectric Power Generation System Based On Concentration And Phase Change Energy Storage

The main bottleneck of applying wireless sensor network(WSN)is the power supply of WSN's node in forest environment monitoring.How to collect and store the environment energy to solve the nodes'power supply has become a research hotspot.This paper proposes a thermoelectric power generation(TEG)system based on solar energy concentration and phase change energy storage.It puts forward a new idea for the power supply of WSN's node in forest environment monitoring.The main content and results are as follows:1.The conversion efficiency of TEG is an important factor in the system and the existing simplified model of the TEG efficiency conversion is constant properties model.To study the effect of the temperature dependence of the Seebeck coefficient,electrical resistivity,and thermal conductivity of thermoelectric material(TE)on the thermoelectric conversion efficiency,the TE differential equation is solved by introducing the volume average of TE material parameters,and a simplified TE element model is established for a TE element with a linear temperature profile.The temperature dependence of the Seebeck coefficient,electrical resistivity and thermal conductivity are incorporated into the thermal conductivity equation,and the TE conversion efficiency is solved.This proposed model is applied to a high-performance N-type half-Heusler alloy,and the obtained maximum conversion efficiency agrees well with the numerical results(with relative error 1.36%)for an average temperature Tm=510 K and temperature difference?T=440 K.The results confirm that the proposed model,which incorporates the Thomson effect,is simple and accurate.It is innovatively proposed that using the volume average of TE parameters converts the variable coefficient TE control differential equation into a constant coefficient differential equation.It obtains a simplified model considering the influence of nonlinear temperature dependence on the conversion efficiency.2.To improve the thermoelectric conversion efficiency of solar thermoelectric power,a Fresnel lens is used to concentrate thermal energy,and a phase change material(PCM)is used to store thermal energy to increase the temperature difference between the hot and cold ends of thermoelectric(TE)sheets.By establishing the energy conversion equilibrium equation to numerical analysis the effects of different concentration ratios on the hot end temperature and thermoelectric conversion efficiency of the system.By selecting different heights of the heat exchanger,the system supplies 1.025 V,0.4204 V,and0.299 V open circuit voltages on average for approximately 30,44 and 53 minutes,respectively.Therefore,the height of the heat exchanger affects the rate of heat energy absorption and release.The reversible operation of the system is conducive to the day and night operation of solar power generation and is more suitable to solving the self-supplying power problem for wireless temperature sensors in forests.3.To further explore the PCM radiator's factors affecting the thermoelectric output of the system and improve the utilization rate of energy storage,it proposes a two-stage TEG-PCM system.The experimental results show that heat source thermal power's influence is more manifest than that of the heat sink's thermal resistance.The inclusion of PCM can reduce the second-stage voltage;however,it can have a longer time.The heat sink configuration has more influence on the second-stage voltage(U₂)than the first-stage voltage(U₁).The single cavity is most suitable for the two-stage TEG system.Under the same power supply,the properties of different PCMs affect the duration of each stage voltage.The experimental results show that the influence of three studied factors on the system's efficiency is:heat source>heat sink's thermal resistance>PCM type.The research results of this paper provide a certain technical foundation and support for the self-powered wireless sensor network of forest environment monitoring.