CAREER: Nonequilibrium effects in thermochemical energy storage: linking microstructure to thermal transport

建筑行业消耗了美国三分之一以上的一次能源，其脱碳对于实现气候和可持续发展目标至关重要。热负荷(例如，空间供暖和热水)占建筑能源使用的很大一部分，这可以通过使用存储热量的热电池来满足需求和供应。在不同的存储材料中，热化学盐具有比相变或敏感存储更高的能量密度，在可再生能源的可逆脱水-水化反应中作为热存储是很有前途的。然而，这些盐类水合物经历了结构变化(即机械应力)和湿热不稳定性(如熔融和溶解)，从而在电池循环(充放电)期间降低了它们的能量密度。为此，本项目的总体研究目标是从机理上了解控制热化学相变的关键因素及其对热质耦合传输的影响。这些基础知识将使开发具有长期稳定性的可逆热电池成为可能，同时培养材料和热科学交叉领域的研究生和本科生。该项目的教育目标是为STEM中传统上代表性不足的学生提供跨学科和体验式的学习机会，并为教师制定课程，以广泛提高能源储存的素养。为了跨越不同的长度(分子、微观和宏观)和时间尺度(化学反应与扩散)的热化学反应，我们将追求三个研究目标：(1)利用不同温度和蒸汽压下的原位热分析来阐明传输的动力学限制；(2)将反应的可逆性与结构稳定性关联起来，并设计促进热循环的复合材料；(3)建立多孔介质中热-流体耦合传输的瞬时和多尺度模型以预测能量和功率密度。在实现这些目标的同时，将开展两项旨在扩大和深化对STEM的参与的教育和外联工作：(Iv)招收多样化的高中生，为教师建立工程学教育；(V)让第一代大学生参与跨学科研究。总体而言，这种方法将揭示现实条件下的结构-性质关系，这将有助于解决长期存在的关于用于热能存储的水合物的能量密度和循环性的问题。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Decarbonization of the buildings sector, which consumes over a third of the primary energy in the United States, is essential to meet climate and sustainability goals. Thermal loads (e.g., space heating and hot water) account for a large portion of building energy use, and this can be satisfied using a thermal battery that stores heat to match demand with supply. Among the different storage materials, thermochemical salts are promising for storing renewable energy as heat as they undergo reversible dehydration-hydration reactions with a higher energy density compared to phase change or sensible storage. However, these salt hydrates experience structural changes (i.e., mechanical stress) and hygrothermal instabilities (e.g., melting and dissolution) that reduce their energy density during cycling of the battery (charge-discharge). To this end, the overall research goal of this project is to provide a mechanistic understanding of the key factors governing thermochemical phase transitions and its impact on coupled heat-and-mass transport. This fundamental knowledge will enable the development of reversible thermal batteries with long-term stability, while training graduate and undergraduate students at the intersection of materials and thermal science. The educational goal of this project is to provide interdisciplinary and experiential learning opportunities for traditionally underrepresented students in STEM, as well as curriculum development for teachers to increase literacy about energy storage broadly. To bridge our understanding of thermochemical reactions across different length (molecular, micro, and macro) and timescales (chemical reaction vs. diffusion), three research objectives will be pursued: (i) Elucidating the kinetic limitations on transport using in situ thermal analysis at different temperatures and vapor pressures, (ii) Correlating reaction reversibility with structural stability, and designing composite materials that facilitate thermal cycling, and (iii) Developing a transient and multiscale model for coupled thermal-fluid transport in porous media to predict energy and power density. These objectives will be pursued in tandem with two education and outreach efforts targeted at broadening and deepening participation in STEM: (iv) recruiting a diverse pool of high school students and establishing engineering education for teachers, and (v) engaging first generation college students in interdisciplinary research. Overall, this approach will reveal structure-property relationships under realistic conditions, which will help address long-standing questions about the energy density and cyclability of salt hydrates for thermal energy storage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.