Effects of side-wall air cooling on solar thermoelectric generation with high aspect-ratio, V-shaped P/N couples
Effects of side-wall air cooling on solar thermoelectric generation with high aspect-ratio, V-shaped P/N couples
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DOI：
10.1063/5.0151168
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发表时间：
2023-06
影响因子：
3.2
通讯作者：
Xinjie Li;Thiraj Mohankumar;J. Bahk
中科院分区：
文献类型：
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作者：
Xinjie Li;Thiraj Mohankumar;J. Bahk
太阳能热电发电机(STEG)通常需要较长的热电(TE)腿和冷端的有效冷却，以增加TE腿之间的温差，从而增加功率输出。研究了TE支路侧壁直接空冷对高深宽比STEG输出功率的影响，以及无额外散热片的V型p型和n型TE对的功率输出。线型金属TE材料焊接在一起，形成V形TE腿阵列，不需要额外的电极，并连接到顶部有太阳能吸收器的陶瓷板上，以完成STEG。研究了STEG在集中太阳光照射下不同风速下的发电性能。进行了有限元模拟，进一步分析了热传导和热电性能。研究发现，虽然侧壁空冷在自然对流和强迫对流两种情况下都有助于保持冷端温度较低，但它也可以降低热端温度，从而减小净温差，从而降低功率输出和效率。TE电偶的部分绝热通过保持较高的热端温度，进一步提高了强迫空气对流条件下的功率输出。研制的STEG在10个太阳的自然对流条件下，最大功率密度为230Wcm2，系统效率为0.023%。效率低的主要原因是所使用的金属TE材料的ZT较低，且支腿长度不优化。我们的模拟表明，在最佳支腿长度下，使用最先进的Bi2Te3合金可以将系统效率提高到2.8%。
Solar thermoelectric generators (STEGs) often require long thermoelectric (TE) legs and efficient cooling at the cold side to increase the temperature difference across TE legs and, thus, the power output. We investigate the effects of direct side-wall air cooling of TE legs on the power output of STEGs fabricated with high aspect-ratio as well as V-shaped p-type and n-type TE couples without additional heat sinks. Wire-type metallic TE materials are welded together to create V-shape TE leg arrays without additional electrodes and attached to a ceramic plate with a solar absorber on top to complete the STEG. The power generation performance of the STEG is investigated with varying wind speed under concentrated solar irradiation. Finite element simulation is performed to further analyze the heat transfer and thermoelectric performance. We find that although sidewall air cooling helps to keep the cold-side temperature cooler in both natural and forced convection regimes, it can also lower the hot-side temperature to reduce the net temperature difference and, thus, the power output and efficiency. Partial thermal insulation of TE couples can further enhance the power output under forced air convection by keeping the hot side temperature higher. The developed STEG achieves a maximum power density of 230 μW/cm2 and a system efficiency of 0.023% under 10 suns with natural convection. The low efficiency was mainly due to the low ZT of the metallic TE materials used and the unoptimized leg length. Our simulation shows that the system efficiency can be improved to 2.8% with state-of-the-art Bi2Te3 alloys at an optimal leg length.