Abstract Thermochemical energy storage using salt hydrates is a promising concept to bridge the gap between supply and demand for solar thermal energy in residential buildings. Using a suitable thermochemical material such as a salt hydrate, a thermal energy storage device, also known as a heat battery, can be created to supply low-temperature thermal energy during colder periods. To generate adequate power from a heat battery for the production of domestic hot tap water or space heating, the hydration rate of the salt hydrate needs to be sufficiently fast. It is hypothesized that the hydration rate of the material increases over multiple charge and discharge cycles due to crack formation and volume increase of the salt hydrate particles. This hypothesis is tested by performing two kinds of experiments: optical microscopy experiments using a micro-climate chamber to evaluate the particle size, and Thermo Gravimetric Analysis (TGA) experiments to determine the hydration rate of the particles. The hydration rate and particle size are input for a nucleation and growth model that takes into account crack formation and particle growth. Optical microscopy experiments show a particle expansion of approximately 30 % over 12 cycles. Typical hydration rates are increased by a factor 15 comparing the first and the 12th TGA cycle. It is shown that particle growth and crack formation significantly contribute to the improvement of the hydration rate. Finally, taking into account crack formation and particle growth in the numerical model results in a good agreement between model and experiments. Such a numerical model can be used for heat battery design.

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循环诱导裂纹形成对 K2CO3 颗粒水化行为的影响：实验和建模

摘要 使用盐水合物进行热化学储能是弥合住宅建筑太阳能热能供需缺口的一个有前景的概念。使用合适的热化学材料（例如盐水合物），可以创建热能储存装置（也称为热电池）以在较冷时期提供低温热能。为了从热电池产生足够的电力用于生产生活热水或取暖，盐水合物的水合速率需要足够快。据推测，由于盐水合物颗粒的裂纹形成和体积增加，材料的水合速率在多次充电和放电循环中增加。通过执行两种实验来检验该假设：使用微气候室的光学显微镜实验来评估颗粒大小，以及热重分析 (TGA) 实验来确定颗粒的水合速率。水化速率和粒径是成核和生长模型的输入，该模型考虑了裂纹形成和颗粒生长。光学显微镜实验表明，经过 12 次循环，粒子膨胀约 30%。与第一次和第 12 次 TGA 循环相比，典型的水合速率增加了 15 倍。结果表明，颗粒生长和裂纹形成显着促进了水化速率的提高。最后，在数值模型中考虑裂纹形成和颗粒生长导致模型和实验之间的良好一致性。这种数值模型可用于热电池设计。