"Wafer-Scale Thermionic Energy Converters?"- Roger T. Howe of Stanford University

About the talk:
Thermionic energy converters (TECs) were conceived in 1915, demonstrated in 1939, and were the focus of huge investments during the Cold War by the U.S. and the Soviet Union. A 6 kW thermionic converter, fabricated using precision machining technology, was flown in 1987 by the Soviet Union. TEC research ramped down in the 1990s and the field withered to a few embers by 2005. I will review the simple physics of TECs and what the barriers have been to applying them to direct heat-to-electricity conversion for terrestrial applications.

Over the past decade, new materials, processes, and device architectures are being explored at Stanford, the Max Planck Institute, and other research groups around the world. I will provide an update on recent progress at Stanford on thermally isolated, suspended micro cathodes inspired by microbolometer infrared imagers. In order to reach useful efficiencies, both very high thermal isolation between the cathode and the anode and a much lower anode work function are needed. Over the past year, two approaches to fabricating anodes with work functions of 1 eV or less have been demonstrated at Stanford: the electrostatic doping of graphene and the surface photovoltage in a semiconductor anode.



Support for the Stanford Colloquium on Computer Systems Seminar Series provided by the Stanford Computer Forum.

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Colloquium on Computer Systems Seminar Series (EE380) presents the current research in design, implementation, analysis, and use of computer systems. Topics range from integrated circuits to operating systems and programming languages. It is free and open to the public, with new lectures each week.

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0:00 Introduction
4:15 Thermionic Energy Converter
6:29 Thermionics Timeline: The Early Days
10:30 A Cold War Application: Space Power
14:28 Thermionic Converter Design Cathode work function sets hot-side temperature
15:46 Barrier Index: a critical parameter
19:00 Microfabricated Thermionic Converters?
20:57 Standard MEMS Thermal Isolation Design
22:34 A Pixelated Suspended Cathode
25:33 Nano-Gap Heat Transfer
28:43 Testing Thermionic Components
29:21 Mixed Alkali Earth Oxide Coatings Lower the Work Function of Tungsten
30:07 Density Functional Theory (DFT) Simulations of Work Function and Formation Energy
32:06 Computation of Thermionic Emission Current from First Principles using DFT
33:14 Work Functions for Cathodes and Anodes
43:08 Topping Cycles for Fossil-Fuel Power Plants: Themoelectronic Triodes
47:03 A 21st Century Application for TEC: Concentrated Solar Thermal Power
48:28 Photon-Enhanced Thermionic Emission (PETE) Energy Diagram
51:04 Tandem Solar Thermal Cycle
55:48 Spark Thermionics @ Cyclotron Road

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