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			14. Toshiba Giga Topaz thermoelectric module  [1] [2] Electrical energy is a cornerstone of the modern lifestyle-which is based on convenience. But as everyone knows, the materials needed to generate electricity are limited. The damage to the environment caused by waste heat-the price we pay for our conveniences-is indisputable and present before our very eyes. This interview involves a discussion of a technology that enables use of high-temperature waste heat from sources like automobiles and factories-a technology not perfected until now. This interview opened my eyes to a vision of the future in which this technology provides remarkable benefits. Naruhito Kondo, Business Development Promotion Office, Business Development Promotion Coordination Division, Industrial and Power Systems & Service Company, Toshiba Corporation 1. A miniature powerhouse! Yoshino(Interviewer): This thermoelectric module developed by Toshiba is something most people have never heard of. Is it something we could use in our everyday lives? Kondo: Although this technology isn't in actual use yet, some products already on the market apply the same basic principle, which is based on differences in temperature. Are you familiar with those small heater/refrigerator units sometimes given away as prizes? Now you find them in home improvement centers. Well, they use a similar technology.   Yoshino: Can you describe the module's internal structure and how it generates power? Kondo: The module incorporates two types of semiconductors, Type P and Type N, in an alternating arrangement and connected by electrodes. Each unit composed of this Type P and Type N combination serves as a battery. By combining many of these in series, we can create a module that generates a significant amount of electricity. The device generates electricity by taking advantage of a temperature difference. With a temperature on the high-temperature side of 500°C and a temperature on the low-temperature side of 20°C, the maximum output density is 1 W/cm2. Yoshino: Could you describe what you needed to do to surpass previous technologies? Kondo: Well, until now, poor heat resistance made it very hard to use devices at temperatures of 300°C or above. A key factor in realizing this technology was successfully developing and applying materials resistant to high temperatures. Another key point was keeping the module enclosed, to keep parts like the semiconductor elements and electrodes from oxidizing-even at high temperatures. We used a highly heat-resistant steel alloy for the high-temperature side. We used copper, which readily transmits heat, for the low-temperature side. These two design choices make it possible to create a device that resists temperatures up to 500°C. Comparison with modules currently on the market:   Units Toshiba Giga TopazTM module Modules currently on the market Giga TopazTM Compact type Midsize type Large type Temperature on high-temperature side [°C ] 500 230 230 230 Temperature on low-temperature side [°C ] 20 30 30 30 Voltage [ V ] 3.6 3.3 1.7 2.4 Current [ A ] 4.2 0.8 8 5 Output [ W ] 15.0 2.5 14.0 19.0 Width × height [ cm ] 3.7 * 3.9 2.9 * 2.9 6.3 * 6.3 7.5 * 7.5 Weight [ g ] 40 14 82 115 Output per unit of surface area [ W / cm2] 1.04 0.30 0.36 0.34 Output per unit of weight [ W / g ] 0.38 0.18 0.17 0.17 The Toshiba thermoelectric module offers high heat resistance and powerful electricity-generating performance. Yoshino: So that explains this unprecedented leap for the industry. Kondo: Right. The technology also incorporates another major leap, known by the specialized term "modularization." Using only materials resistant to high temperatures and achieving high levels of performance results in heat dissipation, which is disadvantageous. The most important thing is to enable dense mounting of the various components to permit the heat to pass through the unit, and to attach these precisely. This means fitting around 100 semiconductors and other numerous compact components into a space the size of a 500-yen coin, and then packaging all of this. This modularization is a key factor in this device. Yoshino: I didn't appreciate this at first, but I think including so many parts inside a device the size of a tiny square of chocolate must have required some impressive technologies. It's no surprise this technology is in the limelight. Page Top