Highly Improved Thermionic Energy Converter

Abstract

Thermionic energy converter (TEC) has recently received significant attention, for it holds potential for clean energy generation with a very high theoretical conversion efficiency (60%). For the latter to be achieved, some of the key hurdles are to be overcome. This paper discusses all these key hurdles along with modelling of solar energy conversion using a TEC with nano-materials and metals, using the modified Richardson-Dushman equation, which best describes the thermionic emission current density from these materials. Using two scenarios: allowing natural heat radiation from the back surface of the collector and using controlled heat collection from the collector to maintain it at a fixed temperature. We then discuss results of simulation of the conversion efficiency as a function of temperatures of emitter and collector, work functions and Fermi energy of emitter and collector at absolute zero temperature, solar insolation, the radius of parabolic concentrator and emissivity of radiating surfaces. We discuss the impact of neglecting the radiation losses on the efficiency evaluation as has been done by other workers recently. We suggest some innovative ways to reduce significantly the space charge effect to make a solar TEC a reality.

Concentrated thermionic solar cells using graphene as the collector: theoretical efficiency limit and design rules

“…When the system is connected to an external load, these emitted electrons traverse across the vacuum gap and are subsequently absorbed by the cooler collector, thus generating electrical power through the system. Compared with current technologies for heat-to-electricity conversion, such as the thermoelectric generator (TEG) [6][7][8] and thermophotovoltaics (TPV) [9], the TIEC operating at higher temperatures possesses substantially a higher theoretical efficiency [5,10] and is thus particularly well suited for concentrated solar thermal-harvesting system and for high-grade waste recovery. For TEGs and TPVs, the hightemperature operation is plagued by multiple fundamental device limitations such as maintaining large temperature gradients in TEGs while minimizing the detrimental heat back-flow, and mitigating the large dark saturation currents in TPVs [11,12].…”

Solar thermal characterization of micropatterned high temperature selective surfaces

“…Solar thermal [1] energy converters have been widely studied for many years and are suitable for both small and large-scale deployment. Solar thermionic energy converters [2,25] are a much more direct and potentially more efficient way of generating electricity from solar energy. A basic thermionic converter consists of a hot cathode, which emits electrons which are collected by a cold anode, generating an electrical current.…”

Numericalsimulation on thermal‐hydraulic and thermoelectric characteristics of theTOPAZ‐IIreactor core

“…Liang et al investigated the thermionic electron emission from a single‐layer graphene, and studied the application of graphene as the TEC's emitter 19 . De et al improved the TEC electrode with nano‐materials and metals, and modified Richardson‐Dushman equation was used to describe the current density from these materials 20 . Rahman et al studied a micro gap vacuum TEC, the loss mechanisms in the TEC were investigated (including the radiative heat transfer in the interelectrode gap and space charge effect) 21 …”