Campbell Matthew F, Celenza Thomas J, Schmitt Felix, Schwede Jared W, Bargatin Igor
Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania Philadelphia PA 19104 USA.
Spark Thermionics, Inc. Emeryville CA 94608 USA.
Adv Sci (Weinh). 2021 Mar 3;8(9):2003812. doi: 10.1002/advs.202003812. eCollection 2021 May.
Thermionic energy converters are solid-state heat engines that have the potential to produce electricity with efficiencies of over 30% and area-specific power densities of 100 Wcm. Despite this prospect, no prototypes reported in the literature have achieved true efficiencies close to this target, and many of the most recent investigations report power densities on the order of mWcm or less. These discrepancies stem in part from the low-temperature (<1300 K) test conditions used to evaluate these devices, the large vacuum gap distances (25-100 µm) employed by these devices, and material challenges related to these devices' electrodes. This review will argue that, for feasible electrode work functions available today, efficient performance requires generating output power densities of >1 Wcm and employing emitter temperatures of 1300 K or higher. With this result in mind, this review provides an overview of historical and current design architectures and comments on their capacity to realize the efficiency and power potential of thermionic energy converters. Also emphasized is the importance of using standardized efficiency metrics to report thermionic energy converter performance data.
热离子能量转换器是固态热机，有潜力以超过30%的效率和100W/cm²的面积比功率密度发电。尽管有这样的前景，但文献中报道的原型机都没有达到接近这一目标的实际效率，而且许多最新研究报告的功率密度在mW/cm²或更低的量级。这些差异部分源于用于评估这些器件的低温（<1300K）测试条件、这些器件采用的较大真空间隙距离（25 - 100μm）以及与这些器件电极相关的材料挑战。本综述将指出，对于目前可用的可行电极功函数，高效性能需要产生大于1W/cm²的输出功率密度并采用1300K或更高的发射极温度。考虑到这一结果，本综述概述了历史和当前的设计架构，并对它们实现热离子能量转换器效率和功率潜力的能力进行了评论。还强调了使用标准化效率指标来报告热离子能量转换器性能数据的重要性。
