Effect of non-uniform illumination on performance of solar thermoelectric generators

Solar thermoelectric generators （STEGs） are heat engines which can generate electricity from concentrated sunlight. The non-uniform illumination caused by the optical concentrator may affect the performance of solar thermoelectric generators. In this paper, a three- dimensional finite element model of solar thermoelectric generators is established. The two-dimensional Gaussian distribution is employed to modify the illumination profiles incident on the thermoelectric generator. Six non-uniformities of solar illumination are investigated while keeping the total energy constant. The influences of non-uniform illumination on the temperature distribution, the voltage distribution, and the maximum output power are respectively discussed. Three thermoelectric generators with 32, 18 and 8 pairs of thermocouples are compared to investigate their capability under non-uniform solar radiation. The result shows that the non-uniformity of the solar illumination has a great effect on the temperature distribution and the voltage distribution. Central thermoelectric legs can achieve a larger temperature difference and generate a larger voltage than peripheral ones. The non-uniform solar illumination will weaken the capability of the TE generator, and the maximum output power decrease by 1.4% among the range of non-uniformity studied in this paper. Reducing the number of the thermoelectric legs for non-uniform solar illumination can greatly increase the performance of the thermoelectric generator.

Solar thermoelectric generator and thermoelectric cooler performance:analysis and comparison using a different shape geometry

Thermoelectric devices are one of the technologies used either to generate electricity by applying a temperature difference using thermal energy or as a heating/cooling system by applying an electrical voltage.The number of materials required to produce a product is an important factor in determining its price.Production costs associated with these materials,as well as their availability and quality,play a crucial role in price determination by manufacturers.In this context,a method that employs a uniform volume distribution was implemented.This approach enabled the analysis to focus on other variables,thereby promoting a more precise and relevant evaluation of overall performance.Based on the finite element method,this study investigated the influence of geometric shape,including Rect-leg,Y-leg,Pin-leg and X-leg designs,on the performance of solar thermoelectric generators and thermoelectric coolers.The study was conducted considering the same hot alumina junction surface that receives solar radiation;however,the ef-fective surface,which corresponded to the heat flow area and had a similar area near the exposed surface,varied depending on the chosen leg geometry,thus impacting the heat flux due to the variation in thermal resistance.In the case of a solar thermoelectric generator,the Rect-leg model,having the same effective surface area,presented the lowest heat loss value resulting from convection and radiation in the heat spreader and the hot alumina plate.Under the same conditions,the Y-leg showed the highest value.The Rect-leg design generated,by using thermal and optical concentration,the highest output power of 0.028 and 0.054 W,and efficiency of 3.47%and 4.7%,respectively,whereas the Y-leg generated lower values of 0.006523 and 0.018744 W for power,and 2.83%and 2.71%for efficiency,respectively.In the case of the thermoelectric coolers,the Y-leg generated the highest temperature difference between the hot and cold sides of 67.28 K at an electric current value of 1.8 A,whereas the Rect-leg,Pin-leg and X-leg generated~66.25,~67.02 and~67.19 K at 6.1,2.7 and 2.6 A.

Wide spectrum solar energy harvesting through an integrated photovoltaic and thermoelectric system

This paper proposes a power system concept that integrates photovoltaic （PV） and thermoelectric （TE） technologies to harvest solar energy from a wide spectral range. By introduction of the ＇spectrum beam splitting＇ technique, short wavelength solar radiation is converted directly into electricity in the PV cells, while the long wavelength segment of the spectrum is used to produce moderate to high temperature thermal energy, which then generates electricity in the TE device. To overcome the intermittent nature of solar radiation, the system is also coupled to a thermal energy storage unit. A systematic analysis of the integrated system is carried out, encompassing the system configuration, material properties, thermal management, and energy storage aspects. We have also attempted to optimize the integrated system. The results indicate that the system configuration and optimization are the most important factors for high overall efficiency.