Auswahl der wissenschaftlichen Literatur zum Thema „Thermoelectric generator, sensor technology, digitalisation“

The integration of electrical functionality into flexible textile structures requires the development of new concepts for flexible conductive material. Conductive and flexible thin films can be generated on non-conductive textile materials by electroless metal deposition. By electroless copper deposition on lyocell-type cellulose fabrics, thin conductive layers with a thickness of approximately 260 nm were prepared. The total copper content of a textile fabric was analyzed to be 147 mg per g of fabric, so that the textile character of the material remains unchanged, which includes, for example, the flexibility and bendability. The flexible material could be used to manufacture a thermoelectric sensor array and generator. This approach enables the formation of a sensor textile with a large number of individual sensors and, at the same time, a reduction in the number of electrical connections, since the conductive textile serves as a common conductive line for all sensors. In combination with aluminum, thermoelectric coefficients of 3–4 µV/K were obtained, which are comparable with copper/aluminum foil and bulk material. Thermoelectric generators, consisting of six junctions using the same material combinations, led to electric output voltages of 0.4 mV for both setups at a temperature difference of 71 K. The results demonstrate the potential of electroless deposition for the production of thin-film-coated flexible textiles, and represent a key technology to achieve the direct integration of electrical sensors and conductors in non-conductive material.

While wireless sensor nodes based on conventional semiconductor technology have revolutionized our understanding of the world in which we live, they are limited to operating in benign environments. This limitation precludes their use in a wide range of industrial, automotive and geological applications, where the required operating temperatures can exceed 200°C. Silicon-on-insulator technology has enabled the development of high temperature electronics, however applications requiring higher temperature operation are becoming apparent. Battery technologies capable of sustaining the required power level in these extreme environments are also a significant challenge. In this work, we present the integration of analog functional primitive circuits capable of interrogating resistive and capacitive sensors to form a wireless sensor node based on silicon carbide technology. The electrical power is provided from the output of a novel self-starting boost converter connected to a thermoelectric generator. Data can be transmitted from the node via frequency modulation of a Colpitts oscillator, for remote post processing. The signal conditioning is realised using JFET based amplifier circuits, designed using a novel JFET compact model, which enables a greater level of confidence than existing models in the literature.

Die vorliegende Arbeit forciert die Steigerung der Leistungsfähigkeit netzautarker thermoelektrischer Systeme. Hierunter werden im Folgenden Apparate verstanden, die mittels thermoelektrischer Generatoren (TEG) thermische Energie in Elektroenergie umwandeln, um damit netzautark und dezentral elektrische Kleinstverbraucher an großtechnischen Anlagen und Maschinen zu speisen. Bei den elektrischen Verbrauchern kann es sich beispielsweise um Sensoren zum Vermessen unterschiedlicher Prozessgrößen handeln. Aber auch eine Energieversorgung von Geräten zur drahtlosen Datenübertragung und Aktoren mit entsprechend geringer Leistungsaufnahme ist mittels netzautarker thermoelektrischer Systeme technisch möglich. Zum Erreichen der Zielstellung werden die TEG zur Energieumwandlung nicht isoliert betrachtet, sondern der optimierte Systemaufbau ganzheitlich forciert. Denn zur Steigerung der Leistungsfähigkeit netzautarker thermoelektrischer Systeme müssen alle Komponenten betrachtet: Angefangen von den TEG über die notwendige Wärmekopplung bis hin zu weiteren Peripheriegeräten. Im Konkreten basiert die in dieser Dissertation dargelegte Entwicklungsarbeit zum einen auf einem mathematischen Modell zur Berechnung verlustbehafteter TEG-Wärmeübertrager-Systeme, zum anderen auf der Entwicklung eines effizienten Wärmeübertragers zur passiven Kühlung thermoelektrischer Module sowie der Darstellung und Diskussion eines Gleichstromwandler-Schaltkreises für die Regelung des Betriebszustands eines angekoppelten TEG.

TE (Thermoelectric) materials have been widely used in clean energy system as low-power generator and Peliter cooler, due to its salient features of being compact, light-weighted, noiseless in operation, highly reliable, and environment friendly. Recently, another application has been explored on TE materials as gas sensors based on Seebeck effect and exothermic reaction of hydrogen oxidation on catalyst. In this paper, a TE hydrogen gas sensor with a simple structure, low energy consumption and a high sensitivity was reported. Bi-Te (bismuth telluride) with a high Seebeck coefficient at room-temperature was deposited onto thin glass substrates by RF magnetron sputtering technology. Four pairs of PN film couples were connected in series to improve the output voltage. Pt/ ACC (Activated Carbon Fiber Cloth) was mounted at the joint of PN couples, acting as catalyst so as to accelerate the oxidation of hydrogen. The influences of reduction temperature and Pt content on the generated temperature difference were investigated. The voltage output and selectivity to combustible gas mixture were measured. Experimental results showed that when exposed to 3vol% H2/ air, as-prepared sensor gave out a high output signal of 33.1mV, and the response time was about 50s with recovery time of 50s.

A prototype energy-harvesting thermoelectric generator (TEG) was designed and fabricated and it is being tested to provide power for wireless sensors used in the health monitoring (monitoring of temperatures, vibrations, strains, etc) of Navy shipboard machinery. TEGs are rugged, reliable, solid-state devices that convert heat directly into electricity without any moving parts. The TEGs designed in this project utilize the heat transfer between shipboard waste heat sources and ambient air to generate electricity. To satisfy the required small design volume of less than one cubic inch, Hi-Z Technology, Inc. (Hi-Z) is using its innovative Quantum Well (QW) thermoelectric technology that provides a factor of four increase in the conversion efficiency, and a large reduction in the design volume over the currently used bulk bismuth-telluride thermoelectics. QWs are nanostructured multi-layer thin films. These wireless sensors can be used to detect cracks, corrosion, impact damage, and temperature and vibration excursions as part of the Condition Based Maintenance (CBM) of the Navy ship machinery. The CBM of ship machinery can be significantly improved by automating the process with the use of self-powered wireless sensors. These power-harvesting TEGs can be used to replace batteries as electrical power sources and to eliminate tethered wires and cables, thus significantly reducing the installation and maintenance costs. The very first QW TEG module anywhere was just successfully tested (it produced electricity from heat). It remains to package this module with thermal insulation in the housing and heat sink, and to test this entire TEG device in a simulated thermal environment of a Navy gas turbine. Following this test, it is planned to attach this device to the surface of a gas turbine on a Navy ship and to test it in its actual environment, in conjunction with a wireless sensor. This power supply for wireless sensors can also be used in health monitoring of equipment in the nuclear and conventional power plants, process plants, and the monitoring of temperatures, vibrations and pressures of steam lines, etc. Hi-Z has chosen this small power supply as the first practical application of its emerging QW TEG technology. However, this technology can also be used on a much larger scale in, for example, recovering the waste heat from the exhaust of the truck and automobile engines, where the generated electricity can be used to eliminate the alternator and thus reduce the load on the engine, improve overall efficiency and reduce fuel consumption.