Metamaterials for Mechanical, Biomechanical and Multiphysical Applications Research Group, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam.
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam.
Molecules. 2021 Feb 25;26(5):1235. doi: 10.3390/molecules26051235.
Thermal energy storage is a technique that has the potential to contribute to future energy grids to reduce fluctuations in supply from renewable energy sources. The principle of energy storage is to drive an endothermic phase change when excess energy is available and to allow the phase change to reverse and release heat when energy demand exceeds supply. Unwanted charge leakage and low heat transfer rates can limit the effectiveness of the units, but both of these problems can be mitigated by incorporating a metal foam into the design of the storage unit. This study demonstrates the benefits of adding copper foam into a thermal energy storage unit based on capric acid enhanced by copper nanoparticles. The volume fraction of nanoparticles and the location and porosity of the foam were optimized using the Taguchi approach to minimize the charge leakage expected from simulations. Placing the foam layer at the bottom of the unit with the maximum possible height and minimum porosity led to the lowest charge time. The optimum concentration of nanoparticles was found to be 4 vol.%, while the maximu possible concentration was 6 vol.%. The use of an optimized design of the enclosure and the optimum fraction of nanoparticles led to a predicted charging time for the unit that was approximately 58% shorter than that of the worst design. A sensitivity analysis shows that the height of the foam layer and its porosity are the dominant variables, and the location of the porous layer and volume fraction of nanoparticles are of secondary importance. Therefore, a well-designed location and size of a metal foam layer could be used to improve the charging speed of thermal energy storage units significantly. In such designs, the porosity and the placement-location of the foam should be considered more strongly than other factors.
热能存储是一种有潜力的技术，可以为未来的能源电网做出贡献，以减少可再生能源供应的波动。储能的原理是在有多余能量时驱动吸热相变化，当能量需求超过供应时允许相变化逆转并释放热量。不需要的电荷泄漏和低传热速率会限制单元的有效性，但这两个问题都可以通过在存储单元的设计中加入金属泡沫来缓解。本研究展示了在基于铜纳米粒子增强癸酸的热能存储单元中添加铜泡沫的好处。使用田口方法优化纳米粒子的体积分数以及泡沫的位置和孔隙率，以最小化模拟中预期的电荷泄漏。将泡沫层放置在单元底部，尽可能高的高度和最小的孔隙率导致充电时间最短。发现最佳纳米粒子浓度为 4 体积%，而最大可能浓度为 6 体积%。优化外壳设计和最佳纳米粒子分数的使用导致单元的预测充电时间比最差设计缩短了约 58%。敏感性分析表明，泡沫层的高度和孔隙率是主要变量，多孔层的位置和纳米粒子的体积分数是次要变量。因此，设计良好的金属泡沫层的位置和尺寸可以显著提高热能存储单元的充电速度。在这样的设计中，应该比其他因素更强烈地考虑泡沫的孔隙率和放置位置。
