Fundamentals of Renewable Energy Processes, 3rd Edition

Chapter 6

Thermionics

6.1 Introduction

Discovered in 1885 by Edison, thermionic emission achieved enormous industrial importance in the 20th century, but only in 1956 was the first thermionic heat-to-electricity converter demonstrated.

It is easy to understand how vacuum thermionic generators work, but the device is impractical owing to the space charge created by the electrons in the inter-electrode space. Introducing a plasma containing positive ions into this space overcame the space charge problem but created additional complications. It became necessary to use plasma, not only to cancel space charge but also as a source of additional electrons. Only this latter solution—the ignited plasma device—holds promise of becoming a useful thermionic ...