Compatibility approach for the improvement of oxide thermoelectric converters for industrial heat recovery applications

Abstract

New ceramic Ca3Co3.9O9+δ /CaMn0.97W0.03O3−δ thermoelectric generators with different cross section areas Ap and An of the p- and the n-type leg are fabricated, characterized, and tested at high temperatures in long-term tests. The variation of the measured power output and the efficiency with changing Ap/An ratio is discussed and compared with calculations based on the measured material properties. The highest conversion efficiencies are reached for ratios close to the one predicted by the compatibility approach, whereas an improper choice of Ap/An leads to a strong reduction of the efficiency. A volume power density of 1.4 W/cm3 and an efficiency of 1.08% are found for the most promising generator (temperature difference ΔT= 734 K and Ap/An= 1.12). The results reveal the major importance of the Ap/An ratio for the conversion efficiency and subsequently cost and weight reduction issues, both crucial for a large scale application of thermoelectric converters. Additionally, the oxide generators proved to be very reliable, as after more than 110 h of high temperature energy conversion, no degradation is observable.

Redox-Promoted Tailoring of the High-Temperature Electrical Performance in Ca3Co4O9 Thermoelectric Materials by Metallic Cobalt Addition

“…With the discovery of attractive TE properties in Na x CoO 2 ceramics in 1997 [15], a lot of effort has been put in the research and development of CoO-based materials, as well as other transition metal oxides [16], which have important 'default' advantages (abundance, low-cost, environmental 'friendliness', low reactivity and high thermochemical stability) over established TE materials, enabling them to be considered for power generation applications at high temperatures and in oxidizing conditions [17][18][19][20][21]. While the best performing n-type TE oxides were found in the family of perovskite-type titanates [22][23][24][25], manganites [26][27][28][29] and ZnO-based materials [30][31][32], one of the most promising p-type TE materials (considered as the best choice for a p-type leg in a high-temperature TE module) continues to be the so-called Ca 3 Co 4 O 9 compound, belonging to the family of misfit-layered cobaltites [26].…”

Adjusting the thermoelectric properties of copper(i) oxide–graphite–polymer pastes and the applications of such flexible composites

“…Although well known thermoelectric materials such as chalcogenides offer a high energy conversion, 1,2 their toxicity and scarcity have demanded a search for alternatives. Materials, such as oxides [3][4][5][6][7] and organic polymers, [8][9][10][11][12][13] have attracted great interest, due to their availability, non-toxicity and small cost.…”

Half‐Heusler materials as model systems for phase‐separated thermoelectrics

“…Unileg modules based on half‐Heusler materials have already been proved to have a high energy density (). Improvement of the achieved values is expected if compatible p‐ and n‐type materials are identified according to their compatibility factor (). In order to achieve the best performance of thermoelectric modules, the n‐ and p‐type materials to be used should be designed to exhibit similar chemical and physical properties ().…”