CAREER: Nonlinear Solid-State Thermal to Electrical Power Generators

摘要非技术性：提出了用于工业废热回收和太阳能-热-电转换模块的固态热电转换装置，例如热电、电子和能斯特发电机。它们提供清洁、无噪音、可靠和绿色能源解决方案。这些器件大多效率较低，限制了它们在市场上的应用。它们大多被研究和设计为在小温差下在线性区域中操作。像任何其他热机一样，效率随着温差的增加而增加。因此，在真实的应用中，期望施加大的温度差以获得更高的输出功率和更高的效率。当施加大的温差时，电子与晶格不平衡，并且在高度非平衡条件下，响应可以是非线性的。在这里，PI将研究高度非平衡和非线性制度的数字使用一个全面的蒙特卡罗方法的电子传输。PI将使用热反射技术对器械操作进行实验研究。实验和数值计算结果将用于设计适合在大温差下工作的固态发电机。这些结果为固态发电机的广泛商业化迈出了一步。PI将与不同的当地项目合作，全年安排研讨会，PI将设计不同的实践活动，并向学生介绍计算机编程，热成像和可再生能源。 技术支持：在固态发电机中，期望经由电子将热从阴极传输到阳极，同时限制经由晶格的热传输。因此，具有高度非平衡电子并在非线性区域中操作是有利的。迄今为止开发的大多数理论工具仅在输出功率小的线性输运状态下有效。在线性输送中，材料优值ZT决定了效率。在非线性区域，ZT不是唯一的相关参数，其他参数，如对流换热系数，电子-声子耦合强度，施加的场和装置的几何形状起重要作用。为了研究非线性机制，PI将开发用于电子-声子输运的Monte Carlo代码，从而能够在大的外加场和不同的器件几何形状下研究电荷，自旋和热输运。包括界面传输的代码的输入将使用第一原理计算。除了该工具的功能外，这些数字代码还将有助于对传输进行基本了解，并有助于开发用于器件分析的分析模型。包括对流/辐射在内的传热问题的完整解决方案将解决效率优化问题的更实际但同样重要的方面。最后，PI将使用热反射成像和热磁表征实验研究非线性输运。这些实验提供了一种方法，用于验证的数值预测和额外的见解的设备操作。

Abstract Nontechnical: Solid-state thermal-to-electrical conversion devices such as thermoelectric, thermionic and Nernst power generators are proposed for industrial waste heat recovery and solar-thermal-electrical conversion modules. They provide a clean, noise-free, reliable and green energy solution. Most of these devices are of low efficiency, which limits their applications in the market. They are mostly studied and designed to operate in the linear regime under small temperature differences. Like any other heat engine, the efficiency increases as the temperature difference increases. Therefore, in real applications, it is desired to impose large temperature differences to obtain higher output powers and higher efficiencies. When large temperature differences are applied, electrons are out of equilibrium with lattice and under highly non-equilibrium conditions, responses can be nonlinear. Here, the PI will study the highly non-equilibrium and nonlinear regime numerically using a comprehensive Monte Carlo method for electron transport. The PI will use thermo-reflectance technique to study the device operation experimentally. The experimental and numerical results will be used to design solid-state power generators suitable to work under large temperature differences. The results serve as a step toward wide commercialization of solid-state power generators. The PI will partner with different local programs to arrange for workshops throughout the year, in which the PI will design different hands-on activities and will introduce students to computer programing, thermal imaging, and renewable energies. Technical: In solid-state power generators, it is desired to transport heat from cathode to anode via electrons while restricting heat transport via lattice. Therefore, it is advantageous to have highly non-equilibrium electrons and operate in the nonlinear regime. Most theoretical tools developed so far are valid only in the linear transport regime where the output powers are small. In the linear transport, materials figure of merit, ZT, determines the efficiency. In the nonlinear regime, ZT is not the only relevant parameter and other parameters such as convective heat transfer coefficient, strength of electron-phonon coupling; applied field and geometry of the device play important roles. To study the nonlinear regime, the PI will develop a Monte Carlo code for electron-phonon transport, enabling investigation of charge, spin and heat transport under large applied fields and for different device geometries. The inputs of the code including interfacial transmission will be calculated using first principles. In addition to the capability of this tool, such numerical codes will help developing a fundamental understanding of transport and insights for developing analytical models for device analysis. The full solution of heat transfer problem including convection/radiation will address more practical but equally important aspect of the efficiency optimization problem. Finally, the PI will use thermo-reflectance imaging and thermomagnetic characterization to study nonlinear transport experimentally. These experiments provide a method for validation of the numerical predictions and additional insights to the device operation.