Ube Industries,Ltd. (President: Kazumasa Tsunemi), building on its longstanding research and development efforts in the area of thermoelectric conversion technology, has succeeded in developing a thermoelectric conversion material that exhibits high efficiency in a moderate temperature range of 250oC - 450oC.
This material is based on a combination of zinc and antimony previously regarded as impractical because of its fragility. Ube has discovered a way of strengthening this material by using a proprietary ceramic manufacturing method to form a sintered body. The new material scores over 1.6 (at 400oC) on the nondimensional performance index ZT, which measures thermoelectric conversion.
Ube has already developed a thermoelectric conversion module (bismuth and tellurium) appropriate for capturing industrial waste heat at lower temperatures (300oC or below). Combining these with the newly developed material can yield units appropriate for capturing waste heat at temperatures of 500oC - 600oC, achieving high efficiency rates of electric conversion of 10% or more.
Possible applications for these thermoelectric conversion modules include manufacturing plants and automobiles, for capturing waste heat and converting it to electric power.
Ube Industries plans to further develop and begin test marketing of mid-temperature-range thermoelectric power conversion applications for the new material in FY04, including large-scale thermoelectric conversion modules and related systems.
The Ube Industries group itself plans to proactively promote the effective use of unutilized energy sources. In FY04, thermoelectric conversion test plants will be set up in factories owned by group member Ube Materials Co. (President: Kazuhiko Mitsui). It is expected that these will help to conserve energy and reduce electricity costs. Ube Materials may consider using these test plants as an opportunity to make advances in the thermoelectric business.
Ube's achievement in developing the new material came in cooperation with two projects: the New Energy and Industrial Technology Development Organization's (NEDO) "Preparatory Studies on High-Efficiency Thermoelectric Conversion Device Development" and the "Development of High-Efficiency Thermoelectric Conversion Systems," overseen by the non-ferrous metals division of the manufacturing bureau of the Ministry of Economy, Trade and Industry.
The company will report on details of the new material on the afternoon of March 30 as part of the 2004 Spring Applied Physics Symposium, to be held March 28 - 31 at Tokyo University of Technology, and again on March 31 at the 2004 Japan Institute of Metals spring conference, to be held March 30 to April 1 at the Okayama Campus of Tokyo Institute of Technology.
As shown in the diagram at right, thermoelectrics refers to a special kind of semiconductor material, which is capable of exploiting differences in temperature to convert heat energy directly into electricity.
The structure is relatively simple, as no moving parts are required. The system is scalable, and it can be dispersed to capture unused heat energy wherever it can be found, helping to conserve energy and protect the environment.
Note: Photomicroscopic image showing microscopic structure of ZnSb-based material.
The cross section of the sample was polished and etched to expose the grain boundary structure.