Planar-type thermally chargeable supercapacitor without an effective heat sink and performance variations with layer thickness and operation conditions
Planar-type thermally chargeable supercapacitor without an effective heat sink and performance variations with layer thickness and operation conditions
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DOI：
10.1016/j.apenergy.2020.114975
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发表时间：
2020-06
期刊：
影响因子：
11.2
通讯作者：
Aqeel Mohammed Abdul Mageeth;Sungjin Park;M. Jeong;Woochul Kim;Choongho Yu
中科院分区：
文献类型：
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作者：
Aqeel Mohammed Abdul Mageeth;Sungjin Park;M. Jeong;Woochul Kim;Choongho Yu
热充电超级电容器（TCSC）是可穿戴和物联网（IoT）电子设备中同时收集和存储能量的良好候选者。在这里，我们报告的平面型TCSC的氧化石墨烯层插入硫酸根离子（SGO）作为电解质/隔膜和还原SGO层（rSGO）作为电极。平面型配置在产生大的温度差方面具有优势，但是由于相对小的横截面积，电荷或电流的量受到限制。此外，这种类型的热能采集器通常由于环境空气的大热阻而遭受小的温差，此时热量没有被散热器或/和强制对流严格地移除。在这里，我们测试了TCSC的性能没有一个有效的散热器时，SGO层的厚度增加沿着与不同浓度的硫酸和湿度。发现SGO越厚，湿度越高，电容越大。TCSC的热功率被测量为高（4.53 mV/K）在50%的相对湿度环境下，和时间依赖的能量收集通过热充电，然后通过放电的能量使用已被证明。模拟了TCSC与皮肤的对流换热系数以及TCSC的热传导系数变化时，TCSC在前臂上的温度分布。在考虑TCSC和皮肤之间的热接触电阻的较高（或较低）对流热传递条件下，对于跨TCSC的较大温度梯度，具有通过TCSC的较高（或较低）热传导是有利的。还对TCSC中的温度分布进行了实验测试，表明TCSC两端的温差保持在约4 °C和输出电压保持在约20 mV是可行的。实验结果可以为在实践中没有有效散热器的可穿戴和分布式电子设备收集热能提供见解。
Thermally chargeable supercapacitor (TCSC) is a good candidate for simultaneous energy harvesting and storage in wearable and internet-of-things (IoT) electronic devices. Here we report planar-type TCSC made of graphene oxide layers intercalated with sulfate ions (SGO) acting as electrolytes/separators and reduced SGO layers (rSGO) as electrodes. The planar type configuration has advantage in creating a large temperature difference but the amount of charge or current is limited due to the relatively small cross sectional area. In addition, this type of thermal energy harvesters often suffer from a small temperature difference due to the large thermal resistance of ambient air when heat is not rigorously removed by a heat sink or/and forced convection. Here, we tested the performance of TCSC without an effective heat sink when the thickness of the SGO layer was increased along with different concentration of sulfuric acid and humidity. It was found that thicker SGO and higher humidity resulted in higher capacitance. The thermopower of TCSC was measured to be high (4.53 mV/K) under 50% relative humidity environment, and time-dependent energy harvesting by thermal charging and then energy usage by electrical discharging have been demonstrated. Temperature distributions in TCSC mounted on a forearm were simulated when the convective heat transfer coefficients on TCSC and skin as well as heat conduction through TCSC are altered. Under higher (or lower) convective heat transfer conditions considering the thermal contact resistance between TCSC and skin, it is advantageous to have higher (or lower) heat conduction through TCSC for larger temperature gradients across TCSC. Temperature distribution in TCSC was also experimentally tested, demonstrating that it is feasible to maintain a temperature difference of ~4 °C across TCSC and an output voltage of ~20 mV. The experimental outcomes could provide insight for harvesting thermal energy for wearable and distributed electronics without an effective heat sink in practice.