复合相变储能材料的制备及其在光热系统中的应用

PREPARATION OF COMPOSITE PHASE CHANGE ENERGY STORAGE MATERIALS AND ITS APPLICATION IN PHOTOTHERMAL SYSTEM

胡先锋

11849353

硕士

材料工程

何祝兵

2020-05-30

2020-07-01

哈尔滨工业大学

深圳

近年来，随着温室气体排放水平不断增加以及化石燃料快速消耗，环境污染和能源短缺的问题日益严峻，因而可再生能源受到了广泛的关注。太阳能作为最重要的清洁能源之一，具有成本低、来源广等优势。相变材料（Phase Change Materials，PCMs）是一种在温度不变的情况下改变物质状态并能提供潜热的物质，在太阳能光热转化和能量存储中起着重要的作用，近年来受到越来越多的关注。通过掺杂高剂量的导热颗粒可以有效提高PCM 的导热性能，但是导热颗粒易于在表面聚集降低光吸收，同时降低 PCM整体储能密度。此研究中，通过集成中低温相变材料 D-甘露醇（D-Mannitol， DM）和高导热乙炔黑纳米颗粒，设计了一种体吸收型太阳能吸收器。该吸收器通过掺入低浓度（0.05wt％）的乙炔黑纳米颗粒，使 DM 在保持较高的相变焓（295.2 kJ/kg）的同时，提高了 PCM 的导热性能。实验结果表明，5.0 wt%的乙炔黑纳米颗粒使得热导率提高了 26.4%，从 DM 的 0.68 W·m-1·K-1 提升至 0.85 W·m-1·K-1。除此之外，乙炔黑纳米颗粒还促进了 DM 的形核，降低了过冷度，改善了热管理性能。通过多种表征手段对比了乙炔黑纳米颗粒不同掺杂浓度下 PCM 的性能，挑选出具有最适宜掺杂浓度（0.05wt％）的复合 PCM，并将其与商业化典型的表面式吸收器进行了实际工作环境下的对比。光热转化试验中，添加乙炔黑纳米颗粒可以有效提高 PCM 的全光谱吸收，将 DM 材料 41.86%光吸收率提高到 90%以上。与传统的表面吸收型 PCM 相比，体吸收型 PCM 显著降低了材料内部的温度差。在同样 10 mm 的厚度下，体吸收的工作模式使得上下表面温差从表面吸收型的 103.1℃降至 62.7℃。除此之外，本研究首次在太阳能热电发电机（Solar Thermoelectric Generator，STEG）系统中研究了 PCM 的光热转化和充放能性能。结果表明，体吸收器在PCM 的底部可以达到 198.2 °C，相应的开路电压为 0.65 V，这些性能数据明显优于表面吸收器的 135.1℃和 0.45 V，表明体吸收模式可以极大提高 PCM 的性能。这种新型低成本、易制备的体吸收型复合相变储能材料为 PCM 的改进提供了一种非常有发展潜力的思路。

In recent years, with the increasing level of greenhouse gas emissions and the rapid consumption of fossil fuels, the problems of environmental pollution and energy shortage have become increasingly serious. So renewable energy has received increasing attention. As one of the most important clean energy, solar energy has the advantages of low cost and wide sources. Phase change materials (PCMs) can change the state of matter and provide latent heat under a constant temperature. PCM plays an important role in solar thermal conversion and energy storage, which have received more and more attention in recent years. Doping with high doses of conductive particles can effectively improve the thermal conductivity of PCM. However, the particles will accumulate on the surface to reduce light absorption and reduce the overall energy storage density of PCM.In this study, by integrating the low-temperature phase change material DMannitol (DM) and acetylene black nanoparticles with high conductivity, a volumetric absorption solar absorber was designed, which was equipped with low concentration (0.05 wt%) of acetylene black nanoparticles. This doping can maintain a high phase change enthalpy (295.2 kJ/kg) of DM, and can effectively improve the thermal conductivity of PCM. 5.0 wt% acetylene black nanoparticles make the thermal conductivity increase by 26.4%, from 0.68 W·m-1·K-1 of pure DM increased to 0.85 W·m-1 ·K-1 . Acetylene black nanoparticles also promote DM nucleation, reduce supercooling, and improve thermal management performance. The performance of PCM with different doping concentrations of acetylene black nanoparticles was compared through various characterization methods. The composite PCM with the most suitable doping concentration (0.05 wt%) was selected and compared in actual work with a commercial typical surface absorber. In the photothermal conversion test, the addition of acetylene black nanoparticles can effectively improve the full spectrum absorption of PCM and increase the 41.86% light absorption rate of pure DM materials to more than 90%. Compared with the traditional surface absorption-type PCM, the volumetric absorption-type PCM significantly reduces the temperature difference inside the material. At the same thickness of 10 mm, the working mode of volumetric absorption reduces the temperature difference between the upper and lower surfaces from the surface absorption type of 103.1°C to 62.7°C.For the first time, the solar thermoelectric generator (STEG) system was studied for the solar thermal conversion and energy charging and discharging performance of PCM. The results show that the volumetric absorber can reach 198.2°C at the bottom of the PCM, and the corresponding open circuit voltage is 0.65 V. These performance data are significantly better than surface absorber. The corresponding results in the surface absorption mode can only reach 135.1℃ and 0.45 V, indicating that the volumetric absorption mode can significantly improve the performance of PCM. This new low-cost, easy-to-prepare volumetric PCM provides a very promising idea for further improvement.

相变材料 光热转化 体吸收 STEG

PCM photothermal conversion volumetric absorber STEG

中文

联合培养

南方科技大学

胡先锋. 复合相变储能材料的制备及其在光热系统中的应用[D]. 深圳. 哈尔滨工业大学,2020.